Properties chemical

Chemical resistance tests are conducted using four different methods  

Handbook of Plastics Testing and Failure Analysis, Third Edition, by Vishu Shah Copyright 2007 by John Wiley Sons, Inc. 

Plastic materials should not be selected solely on the basis of published chemical resistance data. The type of test conducted, test temperature, media concentration, duration of exposure, type of loading, and additives used in the base polymer must be considered, since each of the above-mentioned factors can have a significant effect on the chemical resistance of plastics. The risk potential of premature failure can be minimized by conducting the test under anticipated end-use conditions and media (5). 

Plastics have deeply penetrated the household products market in the last two decades. Determination of stain resistance of plastic materials has become increas- 

Excess staining material is removed from the surface after exposure and the specimen is visually observed for residual staining. Depending upon the specific requirement, the residual staining may or may not be acceptable. The color of plastic has a significant bearing on the noticeability of stains and, therefore, one must consider testing end-use color specimens. 

Chemical properties, ranging from resorbability to chemical stability, can be controlled according to the nature of the crystal, the glass phase or the 

Particularly Favorable Combinations of Properties of Glass-Ceramics (Selection) 

Mechanical property (machinabillty) + thermal properties (temperature resistance) 

Thermal property (zero expansion + temperature resistance) + chemical durability 

Mechanical property (strength) + optical property (translucency) + favorable processing properties 

The general chemical composition of carbon black according to elemental analysis is within the following limits  

The composition depends on the manufacturing process, the raw material, and the chemical aftertreatment. The ash content of most furnace blacks is 1 wt.%. The ash components can result from the raw material, the salts that are injected to control the structure, and the salts of the process water. The ash content of gas blacks is less than 0.02%. 

The surface of carbon blacks contains certain amounts of polynuclear aromatic substances. These are strongly adsorbed and can only be isolated by continuous extraction with solvents, e.g., boiUng toluene. For most industrial carbon blacks, the amount of extractable material is below the Umit defined by the food laws. 

Distillates from coal tar (carbochemical oils), or residual oils that are created by catalytic cracking of mineral oil fractions and olefin manufacture by the thermal cracking of naphtha or gas-oil (petrochemical oil) can also be used as a source of raw material. Quality is the main criteria to favor a specific feedstock. Here a variety 

The chemical properties of uranium are derived from its electronic structure 92 protons and 92 electrons (the number of neutrons varies from 125 to 149). Six electrons are in its outer shell with an electron configuration of [Rn]7s 5U6d so the two most common valence states are +6 with [Rn]5f° configuration and +4 with [Rn]7s configuration. Trivalent and pentavalent compounds are also known, but their commercial importance is quite negligible. When uranium metal is exposed to air, an oxide layer is formed. Finely divided metal is pyrophoric and can ignite spontaneously in air. The chemistry, production, and reactions of some of the most commercially important uranium compounds, especially those that play a role in the NFC, are discussed later. 

In general molybdenum disulphide is chemically very inert. It is resistant to attack by most acids, except aqua regia and hot concentrated sulphuric, nitric and possibly hydrochloric acids. Whereas most metals form salts when attacked by acids, molybdenum has no such tendency, and the product of acid attack is normally molybdenum trioxide. The same appears to be true of the disulphide, and the limited attack by acids can be considered more as a form of oxidation. There is considerable variation in the resistance of different samples to acid attack, and the reactions involved may therefore be primarily those of contaminants rather than of the molybdenum disulphide itself. 

It is attacked by fluorine but there is no reaction with dry hydrogen fluoride, and only a slow reaction with hydrofluoric acid. Reaction with chlorine produces molybdenum pentachloride. Heating in hydrogen reduces the disulphide directly to molybdenum metal. 

Adsorption on molybdenum disulphide is important because of its effect on lubrication, and Kalamazov and co-workers , studied the adsorption of oxygen, hydrogen, nitrogen and water vapour. They found that after desorption at 900°C and 10 Pa (10 Torr) subsequent re-adsorption was at a lower level, and inferred that active adsorption sites had been destroyed by the vacuum and high temperature. They found that at 700°C adsorbed water vapour was dissociated, causing oxidation and the liberation of hydrogen. 

Matsunaga studied adsorption of n-amylamine on cleavage faces and edge sites of the crystals by the use of Auger spectrometry . He confirmed the easy adsorption and slow desorption on crystal edges, and the very slow adsorption and very easy desorption on cleavage faces. This behaviour is discussed later in relation to the effects of contaminants on friction. 

At temperatures above 300°C Holinski found that molybdenum disulphide produced embrittlement of stainless steel. He suggested that free sulphur released at these temperatures reacted with nickel in austenitic alloys to deposit nickel sulphide preferentially at grain boundaries, thus leading to a form of stress corrosion. Knappwost similarly reported that molybdenum disulphide reacted with iron at 700°C to produce ferric sulphide and free molybdenum, and Tsuya et al showed that it reacted more rapidly with iron and nickel than with silver or copper in a vacuum of 10 Torr above 500°C. The reaction with copper was in fact slow above 500°C but very rapid about 700 C. 

3 Water, Chemical and Physical Properties 1.3.1 Chemical Properties 

Water has some almost unique chemical properties which can be explained by the structure of its molecules. 

The charge separation induces temporary dipoles even in non-polar molecules. This explains why water is an excellent solvent. Water can solve and bring together a variety of substances that are the basis for life. 

If the bond were linear, this would have a profound effect for life on Earth. Pure water has a neutral pH of 7 it is neither acidic nor basic. 

Considering a water molecule, the side with the hydrogen atom (positive charge) attracts the oxygen side (negative charge) of a different water molecule. This attraction between two water molecules is also called hydrogen bond (Fig. 1.9). 

Conformation has a major influence on the chemical reactivity of cycloalkanes. To understand its effect in any one reaction, we first need to know what the conformation is of the transition state, and this requires a knowledge of the reaction mechanism. Next, we have to decide what amount of energy is required for the reactants to achieve transition-state conformations. For example, consider the E2 elimination discussed in Section 8-8D. The preferred transition state requires the leaving groups to be antarafacial and coplanar  

For cyclohexane derivatives to react in this way, the transition-state conformation must have both leaving groups axial  

CH2Br (CH2)n + Br2 — (CH2)n-2 very readily3 slowly6 inert inert inert 

CH2Br ch3 (CH2)n + H2S04 — (CH2) 2 readily readily inert inert 

For this reason, compounds such as cw-4-ferr-butylchlorocyclohexane eliminate HC1 much more readily by the E2 mechanism than do the corresponding trans isomers. 

Sulfone polymers exhibit varying levels of chemical compatibility, depending upon their polymeric structure. The chemical compatibility is influ- 

Sulfone-hased polymers show a very good resistance to prolonged chlorine exposure at elevated temperatures. The weight change after an exposure of 6 months to static chlorinated water at 60°C at chlorine levels of up to 30 ppm is essentially zero for Udel , whereas e.g., poly(acetal) exhibits a weight loss of ca. 5% at 30 ppm chlorine in water after 6 months. This property suggests applications in water delivery systems. 

In most cases, the chemical properties of vitreous carbon are similar to those of the graphite crystal, reviewed in Ch. 3, Sec. 7. Since the material has low permeability, is essentially non-porous and free of surface defects, and can be made with very low impurities, its resistance to chemical attack is generally excellent and is one of its outstanding characteristics. In many instances, it is far more chemically resistant than other forms of carbon, such as molded or pyrolytic graphites. 

The presence of impurities (ashes) is very critical. For instance, the rate of oxidation increases by approximately an order of magnitude when the amount of impurities increases by the same ratio, as shown in Fig. 6.7 Thisfigure also shows thatthe oxidation of vitreous ceu bon is much less than that of molded graphite. 

Vitreous carbon does not react with nitric, sulfuric, hydrofluoric, and chromic acids. It is not attacked by halogens such as bromine, even at high temperatures, as opposed to other graphitic materials which are attacked rapidly.t l Its rate of reaction with various reagents is shown in Table 6.3. 

Rgure 6.7. Oxidation rate of vitreous carbon and other carbon products.l l 

Physical State at 20°C — the physical nature of the chemical (solid, liquid, or gas) at 20°C (i.e., room temperature). Changing the temperature may alter the physical state, depending on the magnitude and direction of the change relative to the melting and boiling points of the chemical. 

Octanol/water partition coefficient (Kow) other solvents) 

Boiling Point (BP) — the temperature at which a liquid changes to gas under standard atmospheric pressure (760 mm mercury). The BP of water is 100°C, while the BPs of ethyl alcohol and n-hexane are 78.4°C and 68.7°C, respectively. Lowering the atmospheric pressure (e.g., by applying a vacuum) will lower the BP conversely, higher pressures result in elevated boiling points. 

Melting Point (MP) — the temperature at which a solid changes to a liquid. The melting point is not particularly sensitive to atmospheric pressure, but it is responsive to dissolved salts which depress the melting point. Thus, in winter, it is usual to salt sidewalks to keep water from freezing. 

Fire and Explosion Hazards Handbook of Industrial Chemicals 

The surface of carbonaceous materials contains numerous chemical complexes that are formed during the manufacturing step by oxidation or introduced during post-treatment. The surface complexes are typically chemisorbed oxygen groups such as carbonyl, carboxyl, lactone, quinone, and phenol (see Fig. 3). 

In addition, carbon-hydrogen bonds are present, particularly in carbonaceous materials obtained by carbonizing polymers at low temperatures, typically 1000 °C. Detailed discussions on the types of surface groups and their surface concentrations are presented by Boehm [14] and Rivin [15]. 

A good understanding of the chemical properties of CNTs is mandatory for enhancing the efficiency of practical devices and also for comprehending related fundamental processes such as their electrochemistry. In the following, we will address the chemical reactivity of CNTs and in Section 3.3.3, the different (bio) chemical functionalization procedures that can be performed for applications, will be discussed in more detail. 

One of the outstanding characteristics of silicon carbide is its chemical resistance, which is due to the high affinity of silicon for oxygen. The reaction of silicon with 

SiC material type SiC content (weight-%) Density (g cm - ) Porosity (%) Young modulus (GPa) Thermal expansion 30-1500X (lO K ) Thermal conductivity at 600°C (W mK ) Flexural strength 20°C 1400°C (MPa) (MPa)  

The reaction rate varies with time according to a parabolic law [191], The kinetics are determined by the diffusion of oxygen through the Si02 layer. The temperature dependence of oxidation follows the Arrhenius equation. 

The active oxidation of SiC is distinguished from the passive oxidation reaction described above  

Active oxidation takes place under conditions of oxygen deficiency above 1000°C and leads to decomposition of the SiC and formation of silicon monoxide [194,192], The two forms of corrosion (active, passive) and the conditions for the boundary have been recently discussed by Nickel et al. [195] using examples from SiC- and also Si3N4-based ceramics. A likely high temperature boundary for SiC is w 1700-1800°C, where a secondary active-to-passive transition by bubble formation and spalling occurs. 

Hydrolysis, methanolysis and interesterification are the most important chemical reactions for TGs. 

Hydrolysis. The fat or oil is cleaved or saponified by treatment with alkali (e.g. alcoholic KOH)  

After acidification and extraction, the free fatty acids are recovered as alkali salts (commonly called soaps). This procedure is of interest for analysis of fat or oil samples. Commercially, the free fatty acids are produced by cleaving triglycerides with steam under elevated pressure and temperature and by increasing the reaction rate in the presence of an alkaline catalyst (ZnO, MgO or CaO) or an acidic catalyst (aromatic sulfonic acid). 

Methanolysis. The fatty acids in TG are usually analyzed by gas liquid chromatography, not as free acids, but as methyl esters. The required transesterification is most often achieved by Na-methylate (sodium methoxide) in methanol and in the presence of 2,2-dimethoxypropane to bind the released glycerol. Thus, the reaction proceeds rapidly and quantitatively even at room temperature. 

Interesterification. This reaction is of industrial importance (cf. 14.4.3) since it can change the physical properties of fats or oils or their mixtures without altering the chemical structure of the fatty acids. Both intra- and inter-molecular acyl residue exchanges occur in the reaction until an equilibrium is reached which depends on the structure and composition of the TG molecules. The usual catalyst for interesterification is Na-methylate. 

These may be subdivided into physical phenomena and those where there is chemical reaction the former include the transmission of fluids through plastics barriers (permeation), and the interaction of plastics with solvents, the effects ranging from swelling to solution. Chemical reaction causes permanent change to the polymer. 

The low density of plastics implies a relatively open structure which can be penetrated by fluids, such as water, oxygen or carbon dioxide, during which the barrier material may be affected only marginally. Permeation is especially important in packaging. 

The interaction of plastics with solvents is relevant to the wider use of plastics materials. Solution (for linear polymers) or maximum swelling (for cross-linked systems) is favoured by similarity between polymer repeat unit and the solvent, and by specific interaction between solvent and polymer. On the other hand, solubility is reduced by crystallinity in the plastic, the energy associated with the formation of the crystallites having to be overcome before solution can be effected. Thus, crystalline plastics are considerably more resistant to solvents than are amorphous materials. 

It is not possible on the basis of present knowledge of the relationship of chemical structure to the carcinogenic activity of a chemical to predict how many of the millions of compounds in nature, or the tens of thousands of compounds in commerce, are carcinogenic. Although relatively few chemicals have been observed to cause cancer in human populations, those that have (Thble 5.1), and the himdreds of other substances for which there is some evidence of carcinogenicity in laboratory animals (Thble 5.2), include compounds of widely diverse structures. 

2 Sources and Levels of Carcinogenic Chemicals in the External Elnviromnent 

A brief examination of Thbles 5.1 and 5.2 shows many chemicals that are common in the environment. In contrast to the relatively extensive assessment of human exposure to ionizing radiation, assessment of the extent of human exposures to these and other chemicals is fragmentary. Because there are some 6,000,000 known chemicals (NAS/NRC, 

1984)—60,000 in commerce—the task of measurement is huge. Also, whereas radioactive materials decay with well defined half-lives, the fates of chemicals are much mote diverse. 

Cadmium, certain cadmium compounds Nickel certain nickel compounds 

Perfluorinated surfactants are remarkably stable. Their outstanding thermal and chemical stability permits applications under conditions which would be too severe for conventional hydrocarbon-based surfactants. The very strong C—bond is stable to acids, alkali, oxidation, and reduction, even at relatively high temperatures. 

The unusual properties of fluorosurfactants arise from the unique properties of elemental fluorine [1]  

High electronegativity of covalently bonded fluorine (Table 3.2). Fluorine is the most electronegative element. 

The low dissociation energy of fluorine (Fo — 2F) (Table 3.3) provides a sufficient number of fluorine atoms for a reaction to occur. This is probably the main reason for the high reactivity of elemental fluorine [1]. 

Element Ionization energy Electron affinity s Electronegativity  

Objects molded from classic ABS or ASA copolymers are generally severely attacked by numerous chemical products, such as acids like acetic acid, butyric acid, and nitric acid, phthalates like dioctyl phthalate, gasoline, greases, inks, iodine, alcohols like methanol, motor oils, phenols, glycols, tetrachloroethylene, and acetates like ethyl acetate, amyl acetate, and others (29). 

Compositions based on ASA, ABS and SAN have been described and tested with respect to their chemical resistance. 

ASA types are comparatively impermeable to gases. The gas permeation coefficients of a selected ASA type is shown in Table 12.5. 

Whereas the physical properties of plastics are determined mainly by their morphological structure, their chemical behavior depends mainly on the chemical structure of their macromolecules. Thermoplastics are in most cases resistant to 

1 Transport Mechanisms in Reaction to Chemical Actions (Permeation) 

At first, the low molecular molecule attaches to the surface of the plastic (step 1 adsorption). If the molecule is then unable to penetrate into the plastic, no further 

Chemical properties Resistant to organic solvents, oils, fats, y Relatively resistant to electrolytes 

Not resistant to electrolytes — Show little resistance to organic 

The chemical resistance of polyethylene is, to a large measure, that expected of an alkane. It is not chemically attacked by non-oxidising acids, alkalis and many aqueous solutions. Nitric acid oxidises the polymer, leading to a rise in power factor and to a deterioration in mechanical properties. As with the simple alkanes, halogens combine with the hydrocarbon by means of substitution mechanisms. 

Since polyethylene is a crystalline hydrocarbon polymer incapable of specific interaction and with a melting point of about 100°C, there are no solvents at room temperature. Low-density polymers will dissolve in benzene at about 60°C but the more crystalline high-density polymers only dissolve at temperatures some 20-30°C higher. Materials of similar solubility parameter and low molecular weight will, however, cause swelling, the more so in low-density polymers Table 10.5). 

Low-density polyethylene has a gas permeability in the range normally expected with rubbery materials Table 5.11). This is because in the amorphous zones the free volume and segmental movements facilitate the passage of small molecules. Polymers of the Phillips type (density 0.96 g/cm ) have a permeability of about one-fifth that of the low-density materials. 

Solvent Solubility parameter 8 MPa % increase in weight in polymers  

The reason for the activity of the above named classes of liquids is not fully understood but it has been noted that the most active liquids are those which reduce the molecular cohesion to the greatest extent. It is also noticed that the effect is far more serious where biaxial stresses are involved (a condition which invariably causes a greater tendency to brittleness). Such stresses may be frozen in as a result of molecular orientation during processing or may be due to distortion during use. 

Among thermosetting polymers, epoxy resins are characterized by the highest chemical and corrosion resistance, in addition to optimal resistance to attack from seawater. For these reasons, these thermosetting resins represent the best choice as matrices for composite structures that must retain their mechanical and physical properties and not degrade when immersed in seawater or in a 

Some authors have studied the wet aging of four thermoset resins (orthophthalic polyester, isophthalic polyester, vinyl ester and epoxy) and their composites reinforced with glass fibers. In particular, resins and composites were aged for 18 months, under three immersion conditions i.e. 20°C and 50°C in seawater, and 50°C in distilled water. The experimental tensile tests have shown the inflnence on weight changes particularly of the matrix resin and the aging medinm (Davies et al., 2001). 

Seawater aging of epoxy and vinyl ester resins reinforced with different fibers (e g. glass and carbon) has also been investigated (Narasimha Murthy et al., 2010). The experimental results have evidenced that the vinyl ester composites retain better their mechanical properties than epoxy ones in particular, the flexural strength and ultimate tensile strength (UTS) dropped by about 35% and 27% for glass/epoxy, by 22% and 15% for glass/vinyl ester, by 48% and 34% for carbon/epoxy, and by 28% and 21% for carbon/ vinyl ester composites, respectively. In contrast, the authors have shown that the water uptake of the epoxy-based composites is lower than that of the vinyl ester ones. 

A set of spectra, recorded during stepwise deposition of ZnO onto a decapped Cu(In,Ga)Se2 surface is shown in Fig. 4.26. The ZnO film has been sputtered from an undoped ZnO target using 15 W dc power but otherwise the same standard deposition conditions, which have been used for investigation of the CdS/ZnO interface. On a first inspection no changes in the shape of the peaks is observed during deposition. A chemical reaction between Cu(In,Ga)Se2 and ZnO is, therefore, not evident. 

The O Is spectra do not show the surface species at low coverage in contrast to the CdS/ZnO interface (see Fig.4.19). The difference has already been discussed in Sect. 4.2.2.2, where the absence of the surface species has been attributed to the propensity of the Cu(In,Ga)Se2 surface to dissociate oxygen. However, in case the oxygen can easily dissociate on the surface, an 

Another species might contribute to the chemistry and electronic properties at the interface. As evident from the In MNN spectra shown in Fig. 4.28, there is also sodium present at the surface. The sodium diffuses from the soda lime glass substrate during deposition of the Cu(In,Ga)Se2 film and has a beneficial effect on the solar cell conversion efficiency [139]. As mentioned 

Massive technetium metal tarnishes slowly in a moist atmosphere. In sponge or powder form it is readily oxidized to the volatile heptoxide when heated in air. The metal dissolves in dilute or cone, nitric acid, in cone, sulphuric acid [38J, and in chlorine or bromine water, but not in hydrochloric acid. Technetium dissolves slowly in neutral, ammoniacal or acid hydrogen peroxide solution. The solvents mentioned above oxidize technetium to pertechnetate, in the case of chlorine and bromine water the partial formation of [TcCl J and [TcBreP, respectively, is expected. 

Alkyl halides react mainly by heterolysis of the polar C—X bond. NUCLEOPHIUC DISPLACEMENT 

The equilibrium of nucleophilic displacements favors the side with the weaker Bronsted base the stronger Bronsted base displaces the weaker Bronsted base. The rate of the displacement reaction on the C of a given substrate depends on the nucleophilicity of the attacking base. Basicity and nucleophilicity differ as shown  

Probtom 7.7 What generalizations about the relationship of basicity and nucleophilicity can be made from the following relative rates of nucleophilic displacements  

The order in Problem 7.7(c) may occur because the valence electrons of a larger atom could be more available for bonding with the C, being further away from the nucleus and less firmly held. Alternatively, the greater ease of distortion of the valence shell (induced polarity) makes easier the approach of the larger atom to the C atom. This property is called polarizability. The larger, more polarizable species (e.g. I, Br, S, and P) exhibit enhanced nucleophilicity they are called soft bases. The smaller, more weakly polarizable bases (e.g. N, O, and F) have diminished nucleophilicity they are called hard bases. 

Problem 7.8 Explain why the order of reactivity of Problem 7.7(c) is observed in nonpolar, weakly polar aprotic, and polar protic solvents, but is reversed in polar aprotic solvents. 

Chiral compounds are of wide interest as auxiliaries in asymmetric synthesis. The efficiency of the auxiliary in the process is usually expressed as the ee of the product (eCpfod)- What happens if the chiral auxiliary is not enantiomerically pure One expects a lower ee for the product. From this value one can calculate the maximum ee of the product (eCj ax) by taking into account the enantiomeric excess of the auxiliary, assuming a proportionality between eCprod and eeaux  

The flash point of a fliumiiable liquid is defined as Uic teinperature at which Uie vapors can be ignited midcr conditions defined by the test apparatus and iiieUiod employed. The Uirec major iiieUiods of measuring Uic flash point are  

These are experimental tests that measure the lowest temperature at wliich application of a test flame causes tlie vapor overlying tlie sample to igitite. Tables of flash points for selected substances are available in tlie literature/ 

Many cliciiiical reactions evolve or absorb heat. When applying energy balances (consenatioit law for energy) in tccluiical calculations the heat (enthalpy) of reaction is often indicated in mole units so that tliey can be directly applied to demonstrate its chemical change. To simplify the presentation that follows, examine the equation  

the heat of a reaction is obtained by taking the difference between the heat of formation (AHi) of the products and reactants. If the heat of reaction is negative (exothermic), as is the case of most combustion reactions, tlien energy 

It has been argued that the inorganic chemistry of boron is more diverse and complex than that of any other element in the periodic table. Indeed, it is only during the last three decades that the enormous range of structural types has begun to 

The composition of the technical insecticide varies somewhat between batches. However, the pp isomer usually accounts for 70% or more of the total weight. The o,p isomer is the other major constituent, accounting for some 20% of the technical product. o,p -DDT is more readily degradable and less toxic to insects and vertebrates than the p,p isomer. The presence of small quantities of p,p -DDD deserves mention. Technical DDD has been marketed as an insecticide on its own (rhothane) and the p,p isomer is a reductive metabolite of p,p -DDT. 

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

Thiamine diphosphate (TDP) is an essential coenzyme in carbohydrate metabolism. TDP-dependent enzymes catalyze carbon-carbon bond-breaking and -forming reactions such as a-keto acid decarboxylations (oxidative and non-oxidative) and condensations, as well as ketol transfers (trans- and phospho-ketolation). Some of these processes are illustrated in Fig. 12. 

The finding that thiamine, and even simple thiazolium ring derivatives, can perform many reactions in the absence of the host apoenzyme has allowed detailed analyses of its chemistry [33, 34]. In 1958 Breslow first proposed a mechanism for thiamine catalysis to this day, this mechanism remains as the generally accepted model [35]. NMR deuterium exchange experiments were enlisted to show that the thiazolium C2-proton of thiamine was exchangeable, suggesting that a carbanion zwitterion could be formed at that center. This nucleophilic carbanion was proposed to interact with sites in the substrates. The thiazolium thus acts as an electron sink to stabilize a carbonyl carbanion generated by deprotonation of an aldehydic carbon or decarboxylation of an a-keto acid. The nucleophilic carbonyl equivalent could then react with other electro- 

The reaction path of thiamine-dependent catalysis is essentially unchanged in the presence of an apoenzyme, except that the enzyme active site residues increase reaction rates and yields and influence the substrate and product specificity. The X-ray crystal structures of TDP-dependent enzymes have clarified this view and permitted an understanding of the roles of the individual amino acids of the active site in activating and controlling the thiazolium reactivity [36-40]. 

In the crystal structures of TDP-dependent enzymes, the coenzyme is generally tightly packed within the active site and is maintained in a specific conformation which is conserved in all TDP-dependent enzymes but which is 

The complexity of the environment surrounding the coenzyme has prevented most simple model systems from dramatically enhancing thiamine reactivity or specificity [46-48]. Peptide- or protein-based models have the advantage of presenting a reasonably complex environment to the coenzyme functionality within a water soluble, yet synthetically accessible, scaffold. 

With respect to molecular energetics, one can, iir principle, measure the total energy of a molecule (i.e., tire energy required to separate it into its constituent nuclei and electrons all infinitely separated from one another and at rest). More typically, however, laboratory measurements focus oir Ihermodyiiainic quantities such as enthalpy, free energy, etc., and 

Due to its symmetrical structure, pentaerythritol tetranitrate is characterized by high resistance to many reagents. Thus PETN, differing from the majority of nitric esters, is not readily decomposed by sodium sulphide at 50°C. On the other hand, it is decomposed quite quickly by boiling in a ferrous chloride solution. Boiling with a 2.5% solution of sodium hydroxide causes very slow decomposition, whereas nitrocellulose rapidly decomposes under these conditions. 

Experiments by Aubertein and Rehling [21] have shown that treatment with water at approximately 100°C causes PETN to hydrolyse. At 125°C, and under pressure, hydrolysis proceeds quite quickly, and is considerably speeded up by the presence of 0.1% of HN03. Whether it occurs in water alone or in water acidified with nitric acid, the hydrolysis produces mainly pentaerythritol dinitrate. A dilute sodium hydroxide solution causes PETN to hydrolyse more rapidly than acidified water. PETN neither reduces Fehling s reagent nor enters into addition products with any aromatic nitro compound. In this respect it differs from both nitroerythritol and nitromannitol. 

It has been established experimentally (T. Urbanski, Kwiatkowski, Miladowski [22]) that the addition to pentaerythritol tetranitrate of such nitro compounds as nitrobenzene, nitrotoluene, dinitrobenzene, dinitrotoluene, trinitrobenzene, and trinitrotoluene, decreases its stability as determined by heating to 120-135°C. The degree of decomposition of PETN, heated alone or in mixtures, can be estimated in terms of the pH-values determining the acidity of the decomposition products (Table 32, Fig. 72). 

Change of pH of PETN alone and with TNT on heating at 120°C (T. Urbanski, Kwiatkowski, Miiadowski [22]). 

Indigo is very stable to light and heat. The molecule does not readily undergo electrophilic or nucleophilic substitution. However, it can be successfully sulfo-nated in concentrated sulfuric acid to give the tetrasulfonic acid, and halogenated in nitrobenzene to introduce up to six halogen atoms. 

Indigo is readily reduced by various reducing agents such as zinc dust, sodium dithionite, hydroxyacetone, and hydrogen, or by electrochemical means. In an alkaline medium, a salt (for example the sodium salt) of leuco indigo is produced (3), which can be converted by acids to so-called indigo white (2). 

Oxidation of indigo results in dehydroindigo (4). Oxidation with permanganate or chromate splits the molecule, forming isatin (5). Oxidation and reduction of the indigo system are accompanied by corresponding changes in the spectroscopic properties (see Section 2.4). 

For thousands of years, indigo was produced from plant material containing low concentrations of indican, a precursor of the dye. Indican is split by enzymes and converted to indigo by oxidation. Indigo can be synthesized from D-glucose by genetically modified strains of coli bacteria, presumably by a process that resembles biosynthesis in plants. 

Metal and nonmetal oxides are converted to fluorides or oxyfluorides by reactions with halogen fluorides as illustrated by the following equations  

Metal salts are generally converted to the metal fluorides by reactions with the halogen fluorides, with the metal being oxidized to its highest oxidation state if an excess of the interhalogen is present. 

Finally, the following reaction of nitrosyl fluoride, NOF, with C1F is noteworthy  

The product, N0C1F2, is essentially ionic, and it contains the NO+ (nitrosyl) cation and the C1F2 anion. This polyhalide anion is similar to several others that are known. For example, I3 results when I2 is dissolved in a solution that contains KI  

The X3 and X X2 species are linear. We shall explore the characteristics and behavior of the polyhalide species in greater detail in the next section. 

Problem 14.12 (a) Why do ethers dissolve in cold concentrated H2S04 and separate out when water is added to the solution (b) Why are ethers used as solvents for BF3 and the Grignard reagent  

Notice that two ether molecules coordinate with one Mg atom. 

Problem 14.13 Identify the ethers that are cleaved with excess HI to yield (a) (CH3)3CI and CH3CH2CH2I, (b) cyclohexyl and methyl iodides, (c) l(CH2)5I.  

Problem 14.14 (a) Show how the cleavage of ethers with HI can proceed by an SN2 or an SNl mechanism. (b) Why is HI a better reagent than HBr for this type of reaction (c) Why do reactions with excess HI afford two moles of RI  

The high polarity of the solvent (H20) in reaction (2) favors an SN1 mechanism giving the 3° R+-H 

The standard (appro.xiinately 16-30 C) heat of reaction, AH , is given by 

The autoignition temperature (AIT) or tlte maximum spontaneous ignition temperature is defined as the maximum temperature at which combustion occurs in a combustible bulk gas mixture when tlie temperature of a flammable gas-air mixture is raised in a uniformly heated apparatus. The AIT represents a tlircshold below which chemicals and combustibles can be handled s ely. (The AlTs of selected substances arc available in the literature. ) The AIT is strongly independent on tlie nature of hot surfaces. The AIT may be reduced by as mudi as 100-200°C when the surfaces arc contaminated by dust. When tlie temperature of a flanuiiable mi.xturc is raised to or above the autoignition temperature, ignition is not spontaneous. Most notably in liquids, there is a finite delay before ignition lakes place, i.e., a lapse between the time tlicrc is a flammable mixture reaches its flame temperature and tlie first appearance of a flame. An equation tliat correlates with the ignition temperature is also available in the literature.  

FIGURE 8-3 Ionization Energies of the Main Group Elements. (Data from C. E. Moore, Ionization Potentials and Ionization Limits Derived from the Analyses of Optical Spectra, National Standard Reference Data Series, U. S. National Bureau of Standards, NSRDS-NBS 34, Washington, DC, 1970.) 

Oxidation-reduction reactions of inorganic species can be described in many different ways. For example, hydrogen exhibits oxidation states of -1, 0, and +1. In acidic aqueous solution, these oxidation states occur in the half-reactions 

These oxidation states and their matching reduction potentials are shown in a Latimer diagram as 

FIGURE 8-4 Frost Diagrams for Hydrogen, (a) Acidic solution, (b) Basic solution. 

The half-reaction 2 H -f 2 e ---- H2 is used as the standard for all electrode poten- 

Because of its strongly negative inductive effect, fluorine substitution tends to dramatically increase the acidity of organic acids [24, 25] (Table 1.5). For example, the acidity of trifluoroacetic acid (pK = 0.52) is four orders of magnitude higher than that of acetic acid (pK = 4.76). Even very tveak acids, for example tert-bu-tanol (pKa = 19.0), are converted by fluorination into moderately strong acids ((CF3)3C0H, pK, = 5.4). 

The inductive effect of fluorination also reduces the basicity of organic bases by approximately the same order of magnitude (Table 1.6). In contrast with basicity, the nucleophilicity of amines is influenced much less by fluorinated substituents. 

The chemical stability of pentaerythritol tetranitrate is very high and exceeds that of all other nitric add esters. It withstands the heat test at 80°C for several hours. As heating continues decomposition is gradually perceptible at temperatures above the melting point, i.e. above 140°C. Aubertein and Rehling [21] have found that water is occluded in crystals of PETN purified by recrystallization from acetone-water. The presence of these occlusions has an adverse effect on the results obtained by examinii the stability of penthrite at 132°C. Removal by grinding and drying the crystals improves the result of the stability test. 

Carbon is a fairly inert element and most of its modifications may only be reacted under rather harsh conditions. Nevertheless the entire Organic Chemistry, known exclusively to deal with its compounds alone, is founded on the chemistry of carbon. This apparent contradiction is resolved by the simple compounds being hard to obtain from the elements, but any further reaction being quite easy to achieve. They succeed in impressive variety, mainly due to the manifold ways of carbon bonding with itself (chains, rings, single and multiple bonds, etc.). 

Carbon s chemistry is governed by its position in the fourth main group. In contrast to the higher elements in this group it does not tend to exert only two out of its four valencies. The maximum connectivity, as present, for example, in diamond, is 4. The octet mle is strictly obeyed in covalently bound carbon, yet 

Carbon monoxide and carbon dioxide, respectively, are obtained from reacting carbon with water or oxygen at a sufficiently high temperature. The latter determines the course of the reaction as well as the present amounts of oxygen or water vapor do. The different enthalpies of the oxidative steps may be explained by the destruction of the crystal lattice required in the reaction of solid carbon to give CO. No energy has to be applied for this process in the second step from CO to CO2, so more heat is released here. 

Strong heating of carbon with gaseous sulfur yields carbon disulphide (CS2) in an endothermal reaction. This may be further reacted with elemental chlorine to give carbon tetrachloride. 

With metals and elements such as boron or silicon (in general, with less electronegative elements) carbon forms carbides. Consequently carbon is the electron acceptor in these compounds. There are three different types salt-tike, metallic 

Velocity of sound. A value of 3810m/sec has been quoted for marble [3.1]. 

Calcite is metastable with respect to dolomite in the presence of sea-water (which contains dissolved magnesium). The process of dolomitisation is slow, even in geological terms. It is, however, slowly reversed in the presence of fresh water. 

The thermal decomposition of calcium and magnesium carbonates is described below. 

Solubility in carbon dioxide-free water. The solubility of calcite in distilled water free of carbon dioxide is 14 mg/1 at 25 °C, rising to 18 mg/1 at 75 °C. That of aragonite increases from 15.3 mg/1 at 25 °C to 19.0 mg/1 at 75 °C [3.1]. However, these values are only of academic interest, as natural water contains dissolved carbon dioxide. 

Reaction with carbon dioxide. The increase in solubility of limestones in the presence of carbon dioxide is due to reversible chemical reaction (3.1) and (3.2), which form calcium and magnesium bicarbonates. For example, at 20 °C approximately 30 mg/1 of calcite will dissolve in distilled water at equilibrium with the atmospheric carbon dioxide [3.9]. 

Incorporation of hydrophobic poly(vinyl) moieties through graft copolymerization onto natural polysaccharides results in the decrease of base sensitivity 

Crystalline silica resists the action of most aqueous alkalis and acids, apart from hydrofluoric acid, which reacts with silica to form silicon tetrafluoride, Sip4, which is a volatile substance 4HF+Si02= t Sip4+2H20 

This reaction is made use of in the gravimetric determination of silica. However, crystalline silica is attacked by fused caustic alkalis, and alkaline slags, forming silicates for example, when silica is fused with sodium hydroxide, sodium silicate is formed. Fortunately crystalline silica is not readily attacked by ferric oxide, hence silica bricks are used in open-hearth steel furnaces. 

Whereas the reactivity of silica glass with chemical reagents is similar to that of crystalline silica, silica gel is much more reactive, presumably because it is more finely divided. Apart from its chemical reactivity silica gel is a powerful water-absorbant (hence it is used as a desiccant) and is attacked by aqueous alkalis. 

Acrolein is soluble in water and in many organic solvents including ethanol, acetone, and ether (Table 1.1). Acrolein is a highly reactive molecule with two reactive centers one at the carbon-carbon double bond, and the other at the aldehydic group. Acrolein is extremely volatile, flammable, and explosive (Table 1.1), especially in sunlight or in the presence of alkali or strong acid. A potential hazard in 

Spectrophotometric determination with 4-hexyl-resorcinol and a fluorometric method with m-aminophenol are the most commonly 

These oxidation states and their standard reduction potentials can be depicted in a Latimer diagram, with the oxidation states decreasing from left to right (from the most 

The half-reactions associated with these hydrogen redox conples in basic solntion (1 M OH ) are 

Potentials for nonadjacent pairs of substances (those that share a common species in their reduction half-reactions) can be conveniently derived, as the following example describes. 

Determine the standard reduction potential for the O2/H2O redox couple in acid  

Methanol decomposes to formaldehyde when it is subject to the ultraviolet radiation contained in the sun light, even extraordinarily slowly. The direct oxidation on suitable catalysts and at tempoatures of 650 to 1000°C yields formaldehyde. Dimethyl ether is produced from methanol by dehydration. 

Methanol can be esteriiied using a mixture of sulfuric and nitric acid, converted to methyl chloride with hydrogen chloride and to methyl amines with ammonia. Alkali metals are dissolved by methanol with alkali methylates fcam-ing if this reaction takes place in the presence of CO, methyl formiate occurs. One of the most important reaction occurring in the presence of carbonyl catalysts is CO being taken up by methanol producing acetic acid. 

Pu is a very reactive metal. The potential for the couple Pu = Pu + e is 2.03 volts, which places it between scanditim (Sc) and thorium (Th) in the EMF series of elements, Pu oxidizes more readily than does U, and resembles cerium (Ce) in its reactions in air. Superficial oxidation of a freshly prepared surface occurs in a few hours in normal air. The oxide is more or less adherent, and in several days the oxidation reaction accelerates until finally the oxidation to PuOg is complete. However, the oxide coating protects the underlying metal in dry air, and the oxidation proceeds more slowly. Pu metal is attacked at elevated temperatures by most gases Hg, N2. halogens. SOg, etc. Pu metal dissolves easily and rapidly in moderately concentrated HCl and other halogen acids. 

Pu forms intermetallic compounds with intermediate solid solutions with most metallic elements. However, simple eutectic mixtures are usually made with the group Va and Via metals, and very little solubility in either the liquid or solid state is exhibited by alkali and alkaline earth metals. 

The behavior of Pu toward various solutions is given in Table IV-2. 

Latent heat of transformation to next higher phase (cal/g-atom) 

Body- Orthorhombic Face- Body-or face- Bodj - 

Differentia Scanning Calorimetry (DSQ measurements on [Aus5(PPh3)i2Q6] reveal a sharp exothermic decomposition signal at 156 C. [81] Preparative thermolysis of the compound in solution results in the quantitative stoichiometric reaction (3.35)  

These results agree well with electrochemical experiments. If dichloromethane solutions of different Msj dusters are contacted to Pt electrodes to which 20 V dc is applied, the duster molecules are degraded as a result of the contact with the electrodes. [109] Polarization effects may be the reason for the decomposition. Electrophoresis is observed without any indication of duster decomposition if the platinum electrodes dip into water layers covering the organic phase in a U-tube. The black, thermodynamically unstable microcrystalline products formed on the Pt surfaces have been identified by X-ray powder diffraction to be novel [(Mi3)J metal modifications. The results from the diffraction experiments indicate a structure consisting of cubic dose packed M13 dusters which are linked via their triangular faces to form a kind of pseudo dose packed structure with M13 dusters as building blocks. 

Ikble 3-15. Measured and Calculated Values for the Peak Centers of (Aujs), in the Positive SIMS Spectra of [Aus3(PPh3)i2Cl i]. 

These very preliminary results of catalytic reactions with supported large ligand stabilized clusters are promising. The present experiments indicate a considerably increased activity compared with usual systems. For the present, one may interpret these results in terms of the uniformity of the cluster molecules used because the influence of the ligands is still not understood. 

van der Putten, H.B. Brom, L.J. de Jongh, G. Schmid in Physics and Chemistry of Finite Systems From Clusters to Crystals (Eds. P. Jena, S.N. Khanna, B. K. Rao), Kluwer Acad. Publ. 1992, P. 1007. 

A characteristic of the carbides of Group IV and the monocarbides of Group V is their mutual solubility as shown in Fig. This solubility 

Many ternary carbides and nitrides are known and some of these compounds have excellent properties. For instance, the hardness of ternary-carbide systems of the same group (Group IV or Group V) is considerably higher than the hardness of the binary constituents.1 1 A hardness of approximately 43.1 GPa is reported for the compound TIq 4C 

The study of these ternary (and quaternary) systems is an extensive and promising area but outside the scope of this book (for a general review of these systems, see Ref 24). 

The Group IV carbides are generally chemically inertPJ (see following three sections). 

The interaction with H, N, and O is widely dififer-ent for Mo and W on the one hand, and Nb and Ta on the other. Molybdenum and W have almost no solubility, whereas Nb and Ta can dissolve a considerable amount of these elements. Hydrogen can be removed from Nb at 300 °C to 1600 °C and from Ta at 800 °C to 1800 °C without metal loss by degassing in high vacuum. For the removal of N, temperatures higher than 1600 °C are recommended. The evaporation of volatile oxides at temperatures above 1600 °C in high vacuum leads to a reduction of the oxygen content in Nb and Ta. But during such heat treatments, metal is evaporated simultaneously. 

An overview on the resistance of pure Mo, W, Nb, and Ta against different media is given in Tables 3.1-109 

Refractory metals require protection from oxidizing environment as they do not form protective oxide layers. Oxidation of Mo and W leads to a loss of material by the formation of volatile oxides above 600 °C, but without any significant impact on the mechanical properties. 

There is extensive evidence that between 300 and 500 °C, oxide-dispersion-strengthened (ODS) refractory metal alloys (e.g.. Mo—LaaOs and Mo—Y2O3 grades) possess markedly reduced oxidation rates compared to the pure metals [1.133]. In-situ oxidation and evaluation of the binding state reveal that M0O2 dominates over M0O3 both for Mo and Mo- 

Corroding agent (aqueous solution) Temperature Metal loss (mm/yr) Mo 1 W 1 t  

With the exception of Rb2Th(N03)e, Cs2Th(N03)6 and K3Th(N03)7 all the complexes mentioned in the preceding paragraph are very hygroscopic all the compounds dissolve readily in water and are soluble in nitric acid [1]. Solubility data for Cs2Th(N03)e are illustrated in Fig. 37 [13]. NaTh(N03)s 8.5 H2O and the alkaline earth hydrated complexes are reported to dissolve in ethanol [1]. 

Solubility of Alkyldimethylbenzylammonium Hexanitratothorates(iV) in Nitric Acid Solutions 

The —S—S— link-breaking process can take place under the action of nucleophilic or electrophilic agents [41]. 

For example, under the action of nucleophilic agents, desulfuration can occur according to the following reactions [41)  

These reactions are based on the exchange of tioanion with HO ion, the affinity of which toward sulfur is larger. 

More frequent are nucleophilic decompositions of —S—S— links. These can be achieved with the participation of sulfides, disulfides, and inorganic hydrosulfide, used individually or in mixture with Na2S03- The following reactions take place [421  

Sodium hydrosulfide is usually employed together with sodium sulfite, and in this case the following chemical reactions take place  

In addition to the carboxy-group, most natural long-chain acids contain one or more olefinic and/or acetylenic centres and, occasionally, an additional oxygenated function (hydroxy or epoxy). The reactions and interactions of these polyfunctional systems continue to be actively explored. 

Morrison, M. D. Barratt, and R. Aneja, Chem. andPhys. Lipids, 1970, 4, 47. 

Holman, ibid., p. 869 R. A. Hites, Analyt. Chem., 

Samuelsson and B. Samuelsson, Chem. and Phys. Lipids, 1970, 5, 44 K. Samuels- 

Data from [93] Low D PLA from Cargill press film (0.5 x4 x 10 mm)  

Hydrogels have received increasing interest for biomedical and consumer products application [98]. PLA and PEG hydrophilic/hydrophobic block copolymers are especially promising for soluble hydrophilic/hydrophobic system that becomes an insoluble microsphere when injected into the body as drug release systems [99]. The hydrolysis and biodegradation of these copolymers are subjects of ongoing research. 

Huang in Encyclopedia of Polymer Science and Engineering, Ed., J.I. Kroschwitz and H.E Mark, John Wiley Sons, New York, NY, USA, 1985, Volume 2, p.220-243. 

Degradable Polymers, Recycling, and Plastics Waste Management, Eds., A-C. Albertsson and S.J. Huang, Marcel Dekker, Inc., New York NY, USA, 1995. 

Polymers from Renewable Resources Biopolyesters and Biocatalysis, Eds., C. Scholz and R. Gross, ACS Symposium Series No.764, American Chemical Society, Washington, DC, USA, 2000. 

Chlorosulfonic acid is a powerful acid with a relatively weak sulfur-chlorine bond. It ftimes in moist air producing pungent clouds of hydrogen chloride and sulfuric acid (Equation 1). 

When chlorosulfonic acid is heated it partially decomposes into sulfliryl chloride (SO2CI2), sulfuric acid, sulfur trioxide, pyrosulfuric acid (H2S2O7), hydrogen chloride, pyrosulfuryl chloride (CI2S2O5) and other compounds. At 170 °C, there is an equilibrium between chlorosulfonic acid, sulfuryl chloride and sulfuric acid (Equation 2). Sulfur dioxide and chlorine are not observed when chlorosulfonic acid is heated between 170 and 190 °C, but do appear at higher temperatures or when it is heated in a sealed tube (Equation 3).  

With primary or secondary amines, chlorosulfonic acid yields the corresponding sulfamic acid (Equation 5) this reaction with cyclohexylamine afforded the artificial sweetener sodium cyclamate 3 (Equation 9). In contrast to alkanes, alkenes readily react with chlorosulfonic acid to give the alkyl chlorosulfonates thus ethylene (ethene) is absorbed by chlorosulfonic acid to give ethyl chlorosul-fonate 4 (Equation 10). 

Aromatic hydrocarbons also react smoothly with an equimolar amount of chlorosulfonic acid or an excess of the reagent to yield either the sulfonic acid or the sulfonyl chloride (Equations 6 and 7). The direct conversion of aromatic compounds into their sulfonyl chlorides (chlorosulfonation or chlorosulfonylation) is probably the most important reaction of chlorosulfonic acid because sulfonyl chlorides are intermediates in the synthesis of a wide range of sulfonyl derivatives. The process is of wide application because many substituents on the aromatic ring, e.g. alkyl, alkoxy, amide, carboxy, cyano, hydroxy, nitro and multiple bonds are unaffected by the reagent. 

Chlorosulfonation is essentially an electrophilic substitution reaction, consequently the reaction is facilitated by the presence of electron-donor groups, like alkyl, alkoxy and hydroxy, when it proceeds under relatively mild conditions, e.g. the minimum excess (approx, two equivalents) of the reagent, temperatures of —5 °C to 25 °C and an inert diluent such as chloroform. On the other hand, when electron-withdrawing groups, e.g. nitro, carbonyl or carboxy are present, the reaction requires more drastic conditions, e.g. a large excess of the reagent (five to ten equivalents) and heating to 100-150 °C.  

Nitrogen is usually present in minor amounts, but sulfur can be present in high concentrations, 1%, depending on the precursor that is used to manufacture the carbonaceous material. Besides sulfur that is bonded to carbon, other forms such as elemental sulfur, inorganic sulfate, and organosulfur compounds may be present. The carbon-sulfur surface compounds on carbon blacks are relatively stable, but they desorb as H2S when carbon is heat-treated in H2 between 500 and 1000°C. 

The surface oxide groups on carbon play a major role in its surface properties for example, the wettability in aqueous electrolytes, work function, and pH in water are strongly affected by the presence of surface groups on the carbonaceous material. Typically, the wettability of carbon blacks increases as the concentration of surface oxides increases [16]. The pH of an aqueous slurry of carbon decreases as the volatile or oxygen content of the carbon increases [17]. The work function of carbon blacks shows a minimum at a pH near 6 [18]. 

The physicochemical properties of carbonaceous materials can be altered in a predictable manner by different types of treatments. For example, heat treatment of soft carbons, depending on the temperature, leads to an increase in the crystallite parameters, and Lc and a decrease in the d(0 0 2) spacing. Besides these physical changes in the carbon material, other properties such as the electrical conductivity and chemical reactivity are changed. A review of the electronic properties of graphite and other types of carbonaceous materials is presented by Spain [3j. 

IR-spectrum of EDOT (neat film between KBr windows). 

The most remarkable EDOT reactions are its oxidation reactions, typically resulting in conductive oligomeric to polymeric materials in the presence of charge balancing, so-called doping counterions (anions). These reactions and syntheses will be discussed in detail later (Chapters 7 through 9). 

There are several other reaction pathways not leading to conductive polythiophenes, which will be in the focus of this chapter. Nevertheless, a lot of them are closely related to the essential EDOT chemistry, that is, the tendency to form electrically active oligomers and polymers. 

A simple, but mechanistically important feature is the ability of EDOT and a limited number of derivatives to be protonated in a-position of the thiophene ring by strong acids. The protonation—for example, performed by sulfuric acid or organic sulfonic acids, and more efficiently by trifluoro acetic acid—results in the formation of an active, electrophilic [EDOT-H]+ intermediate. Hydrochloric acid leads to additional side reactions trichloro acetic acid is far less achve than the fluoro analog. The [EDOT-H]+ is able to reversibly add to the basic C-2 of another EDOT molecule. The now formed intermediate may deprotonate to a dimeric structure, a 1,4-dihydro-thiophene derivative (see Eigure 5.10).  

All isomeric products of acid-catalyzed EDOT-di- and trimerization. 

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BrCHi CHjBr. A colourless liquid with a sweet odour, m.p. 10°C, b.p. 132°C. Manufactured by passing ethene through bromine or bromine and water at about 20 C. Chemical properties similar to those of 1,2-dichloroethane when heated with alkali hydroxides, vinyl bromide is formed. Used extensively in petrols to combine with the lead formed by the decomposition of lead tetraethyl, as a fumigant for stored products and as a nematocide. 

Although isotopes have similar chemical properties, their slight difference in mass causes slight differences in physical properties. Use of this is made in isotopic separation pro cesses using techniques such as fractional distillation, exchange reactions, diffusion, electrolysis and electromagnetic methods. 

Overall Physical and Chemical Properties of Crude Oils Related to Transport, Storage And Price... 

Crude oils present a wide variety of physical and chemical properties. Among the more important characteristics are the following ... 

There is a large volume of contemporary literature dealing with the structure and chemical properties of species adsorbed at the solid-solution interface, making use of various spectroscopic and laser excitation techniques. Much of it is phenomenologically oriented and does not contribute in any clear way to the surface chemistry of the system included are many studies aimed at the eventual achievement of solar energy conversion. What follows here is a summary of a small fraction of this literature, consisting of references which are representative and which also yield some specific information about the adsorbed state. 

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Is 2s 2p 3s 3p 3d 4s. If the 3d states were truly core states, then one might expect copper to resemble potassium as its atomic configuration is ls 2s 2p 3s 3p 4s The strong differences between copper and potassium in temis of their chemical properties suggest that the 3d states interact strongly with the valence electrons. This is reflected in the energy band structure of copper (figure Al.3.27). 

Systematic experimental investigations of these transport effects on reaction rates can either be done by varying solvents in a homologous series to change viscosity without affecting other physicochemical or chemical properties... 

Another method by which metals can be protected from corrosion is called alloying. An alloy is a multicomponent solid solution whose physical and chemical properties can be tailored by varying the alloy composition. 

Another example of epitaxy is tin growdi on the (100) surfaces of InSb or CdTe a = 6.49 A) [14]. At room temperature, elemental tin is metallic and adopts a bet crystal structure ( white tin ) with a lattice constant of 5.83 A. However, upon deposition on either of the two above-mentioned surfaces, tin is transfonned into the diamond structure ( grey tin ) with a = 6.49 A and essentially no misfit at the interface. Furtliennore, since grey tin is a semiconductor, then a novel heterojunction material can be fabricated. It is evident that epitaxial growth can be exploited to synthesize materials with novel physical and chemical properties. 

The scope of tire following article is to survey the physical and chemical properties of tire tliird modification of carbon, namely [60]fullerene and its higher analogues. The entluisiasm tliat was triggered by tliese spherical carbon allotropes resulted in an epidemic-like number of publications in tire early to mid-1990s. In more recent years tire field of fullerene chemistry is, however, dominated by tire organic functionalization of tire highly reactive fullerene... 

Characterization of zeolites is primarily carried out to assess tire quality of materials obtained from syntliesis and postsyntlietic modifications. Secondly, it facilitates tire understanding of tire relation between physical and chemical properties of zeolites and tlieir behaviour in certain applications. For tliis task, especially, in situ characterization metliods have become increasingly more important, tliat is, techniques which probe tire zeolite under actual process conditions. 

Among the metals, for example, sodium and potassium are similar to each other and form similar compounds. Copper and iron are also metals having similar chemical properties but these metals are clearly different from sodium and potassium—the latter being soft metals forming mainly colourless compounds, whilst copper and iron are hard metals and form mainly coloured compounds. 

Among the non-metals, nitrogen and chlorine, for example, are gases, but phosphorus, which resembles nitrogen chemically, is a solid, as is iodine which chemically resembles chlorine. Clearly we have to consider the physical and chemical properties of the elements and their compounds if we are to establish a meaningful classification. 

Mendeleef drew up a table of elements considering the chemical properties, notably the valencies, of the elements as exhibited in their oxides and hydrides. A part of Mendeleefs table is shown in Figure 1.2 -note that he divided the elements into vertical columns called groups and into horizontal rows called periods or series. Most of the groups were further divided into sub-groups, for example Groups... 

Chemical properties and spectroscopic data support the view that in the elements rubidium to xenon, atomic numbers 37-54, the 5s, 4d 5p levels fill up. This is best seen by reference to the modern periodic table p. (i). Note that at the end of the fifth period the n = 4 quantum level contains 18 electrons but still has a vacant set of 4/ orbitals. 

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