Basic Reaction

Calcium aluminate cements (CAC) have a wide range of alumina content (38 to 90%). The chemistry and principle cement-water reactions for high alumina cement—a widely used non-portland eement—are described in detail in Ch. 9. The primary binding phase is calcium monoaluminate (CaAl204 or CA). Refractory cements contain higher alumina contents (70 to 90%). 

In CAC, the CA reacts with water to form a series of calcium aluminate hydrates. These include CAHjq, C2AHg, C3AH6, and AH3 (an amorphous phase). The metastable hydrates, CAHjq and C2AHg, convert to C3AH6. The following scheme summarizes the eonversion reactions. 

The conversion that occurs as a consequence of the transformation of the hexagonal phases, CAH q or C2AHg, into the cubic phase, C3AH5, is known to be accompanied by a loss of strength of the hardened alumina cement. 

The conversion reactions themselves are described according to the following equations  

The conversion of CAH q to C3AH5 results in a volume decrease to about 50% whereas that of C2AH8 to the cubic phase results in a decrease of about 65% of the original volume of the reactants. It is apparent that methods to identify and determine the amounts of the aluminate hydrates in CAC concretes are useful for a meaningful diagnosis of potential problems. 

A PEM fuel cell consists of an electrolyte sandwiched between two electrodes. At the surfaces of the two electrodes, two electrochemical reactions take place. At the anode, over which hydrogen gas passes, occurs the HOR. At flie cafliode, over which oxygen or air passes, occurs the ORR. The two electrode reactions are as follows  

The ORR is well recognized as sluggish. The slow kinetics constitutes one of the major voltage losses due to a high reduction overpotential in the performance of a 

and is one of the most limiting factors in the energy conversion efficiency of the state-of-the-art PEMFC [52], Thus, investigation of the ORR remains a major foeus of PEMFC research [53-56]. 

Transition metal complexes with porphjTin ligands [71-73] 

Transition metal complexes with non-porphjTin ligands [74-78] 

A urethane group forms in the reaction between an isocyanate and a hydroxyl group. The active hydrogen atom on the hydroxyl reacts with nitrogen of the isocyanate  

Isocyanates will react in a similar manner with other compounds containing active hydrogens  

If the functionality of the reagents exceeds unity polymers will form. Thus, the use of di-isocyanates and dihydric alcohols (glycols) give the fundamental polyurethanes. One of the first of these was an early synthetic fibre Perlon U, made by Bayer from 1,4 butane diol and hexamethylene diisocyanate  

Linear products result if the reactants are bifunctional, as in the case of Perlon U. Higher functionality leads to the formation of branched chain or crosslinked materials. This tendency is enhanced by the additional reaction of the isocyanate with the urethane, urea, or amide groups already introduced during initial polymer formation, reactions (a), (b), (c) above. The hydrogen on the urethane, urea or amide group is still active, and attacks a further isocyanate group. 

The above reactions, (e), (f) and (g) are important in crosslinking to complex polyurethane structures. 

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Table 1.2 lists several examples of condensation reactions and products. Since the reacting monomers can contain different numbers of carbon atoms between functional groups, there are quite a lot of variations possible among these basic reaction types. 

Nucleophilic Addition. Nucleophilic reagents attack the -carbon position in the conjugated maleic and fumaric frameworks. Basic reaction conditions favor these condensations for the addition of glycolate (21) to maleate [142-44-9] (22) ... 

Acid Chloride Reaction. In situations where the reactants are sensitive to high temperature or the polymer degrades before the melt poiat is reached, the acid chloride route is often used to produce the polyamide (47). The basic reaction ia the presence of a base, B , is as follows ... 

The neat resin preparation for PPS is quite compHcated, despite the fact that the overall polymerization reaction appears to be simple. Several commercial PPS polymerization processes that feature some steps in common have been described (1,2). At least three different mechanisms have been pubUshed in an attempt to describe the basic reaction of a sodium sulfide equivalent and -dichlorobenzene these are S Ar (13,16,19), radical cation (20,21), and Buimett s (22) Sj l radical anion (23—25) mechanisms. The benzyne mechanism was ruled out (16) based on the observation that the para-substitution pattern of the monomer, -dichlorobenzene, is retained in the repeating unit of the polymer. Demonstration that the step-growth polymerization of sodium sulfide and /)-dichlorohenzene proceeds via the S Ar mechanism is fairly recent (1991) (26). Eurther complexity in the polymerization is the incorporation of comonomers that alter the polymer stmcture, thereby modifying the properties of the polymer. Additionally, post-polymerization treatments can be utilized, which modify the properties of the polymer. Preparation of the neat resin is an area of significant latitude and extreme importance for the end user. 

Nitrosyl chloride, a product of the basic reaction, has no commercial value and is converted to salable chlorine and to nitric acid for recycling. 

Analysis of a method of maximizing the usefiilness of smaH pilot units in achieving similitude is described in Reference 67. The pilot unit should be designed to produce fully developed large bubbles or slugs as rapidly as possible above the inlet. UsuaHy, the basic reaction conditions of feed composition, temperature, pressure, and catalyst activity are kept constant. Constant catalyst activity usuaHy requires use of the same particle size distribution and therefore constant minimum fluidization velocity which is usuaHy much less than the superficial gas velocity. Mass transport from the bubble by diffusion may be less than by convective exchange between the bubble and the surrounding emulsion phase. 

Reaction with Other Halides. Bromide ion is oxidi2ed by chlorine to bromine. This is the basic reaction in the production of bromine from seawater, brines, or bitterns. 

After thorough mixing, the mixture is roasted in a mechanical furnace, usually a rotary kiln. An oxidizing atmosphere is essential, and the basic reaction of a theoretical chromite is... 

Cycloalkyl esters have.been used to protect the /3-CO2H group in aspartyl peptides to minimize aspartimide formation during acidic or basic reactions. Aspartimide foimation is limited to 2-3% in TFA (20 h, 25°), 5-7% with HF at 0°, and 1.5-4% TfOH (thioanisole in TFA). Cycloalkyl esters are also stable to Et3N, whereas use of the benzyl ester leads to 25 % aspartimide formation during Et3N treatment. Cycloalkyl esters are stable to CF3COOH, but are readily cleaved with HF or TfOH. - ... 

High molecular weight polycarbonates may be produced without undue difficulty by the phosgenation process. The basic reaction is as shown in Figure 20.5. 

C4 cuts, after extraction of butadiene, are preferred as feed to isobutylene extraction units because the isobutylene concentration (about 30-40%) is higher than in C4 streams from catalytic cracking. The basic reaction in isobutylene extraction is the reversible hydration of isobutylene to tertiary butyl alcohol in the presence of sulfuric acid. 

Aluminium oxide is available in grades with neutral, acidic and basic reactions, which can also vary in the specific surface area and pore size. This makes the separations achieved vary and care must be taken to document precisely. 

Many functional groups are stable to alkaline hydrogen peroxide. Acetate esters are usually hydrolyzed under the reaction conditions although methods have been developed to prevent hydrolysis.For the preparation of the 4,5-oxiranes of desoxycorticosterone, hydrocortisone, and cortisone, the alkali-sensitive ketol side chains must be protected with a base-resistant group, e.g., the tetrahydropyranyl ether or the ethylene ketal derivative. Sodium carbonate has been used successfully as a base with unprotected ketol side chains, but it should be noted that some ketols are sensitive to sodium carbonate in the absence of hydrogen peroxide. The spiroketal side chain of the sapogenins is stable to the basic reaction conditions. 

Either the iodo carbamate (96) or the iodo amine salt (94) from above can be converted to the aziridine by refluxing about 2.5 g of the respective product in 100 ml of ethanol which contains 10 ml of water and 10 g of potassium hydroxide for ca. 2 hr. The aziridine is then isolated by pouring the basic reaction mixture into 250 ml water and extracting with 200 ml ether. The ether extract is washed several times with water and dried (MgS04). Evaporation of the ether on a steam bath yields 2j5,3j5-iminocholestane (95, 25-95 %) as a clear oil which solidifies on standing mp 103-105°. This aziridine is not easily crystallized. 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

Epi and cata substituents show a linear correlation between nucleophilic reactivity of 4-chloroquinoline and basicity (reaction... 

A mixture of 31 5 g (0.1 mol) of 2-chloro-9-(3 -dimethylaminopropylidene)-thiaxanthene (MP 97°C) and 100 g of N-( 3-hydroxyethyl)-piperazine is heated to 130°C and boiled under reflux at this temperature for 48 hours. After cooling, the excess of N-( 3-hydroxyethyl)-piperazine Is evaporated in vacuo, and the residue is dissolved in ether. The ether phase is washed with water and extracted with dilute acetic acid, and 2-chloro-9-[3 -N-(N - -hydroxy-ethyD-piperazinylpropylidene] -thiaxanthene separated from the aqueous acetic acid solution by addition of dilute sodium hydroxide solution to basic reaction. The free base is extracted with ether, the ether phase dried over potassium carbonate, the ether evaporated and the residue dissolved in absolute ethanol. By complete neutralization of the ethanolic solution with a solution of dry hydrogen chloride in absolute ethanol, the dihydrochloride of 2-chloro-9-[3 -N-(N -(3-hydroxyethyl)-piperazinylpropylidene] -thiaxanthene is produced and crystallizes out as a white substance melting at about 250°C to 260°C with decomposition. The yield is 32 g. 

Figure 14-17A. Basic reaction and impulse turbine principles. (Used by permission Rowley, L N., B. G. A. Skrotzki and W. A. Vopat. Power, Dec. 1945. McGraw-Hill, Inc. All rights reserved.)...

Nickel can also be deposited by reduction with the aid of boranates such as sodium boranate (NaBH4) or A-diethyl borazane, i.e. (C2Hj)2NH-BH3, the basic reaction proceeding as follows ... 

Generally, both sodium methoxide and ethoxide are employed as basic catalysts, but sometimes potassium methoxide or sodium hydride67 is used. The alkali salts of the dicarboxylic acids are primarily formed, due to the basic reaction conditions, but after acidic workup the free acids are obtained in 20-60 % yield. Reesterification65 of the acids can be performed (see Section 2.1.4.3.). This method can also be applied to the synthesis of hetarenothiepins such as furanothiepins.67... 

Depending on the degree of oxygen infiltration, the temperature of the condensate and the presence of other gases such as carbon dioxide, various corrosion reactions may take place in the steam distribution and CR systems. The most basic reaction associated with oxygen infiltration results in oxygen corrosion, which can produce deep pitting in the pipework and is described later in this chapter. 

There are four basic reactions that take place. 

Several dihydrotetrazine materials have been promoted as oxygen scavengers, including 3,6-dimethyl,1-2-dihydro,1,2,4,5-tetrazine, and the diethyl- and diphenyl-derivatives. 3,6-Dimethyl,1-2-dihydro,1,2,4,5-tetrazine is a six-sided ring with a formula H3C-CN2C-CH3NHNH its MW equals 102. Its basic reaction with oxygen is shown here ... 

The basic reactions of the sol-gel procedure are shown in Eqs. (1-3), in which the species of Si—OH are the key intermediates. These Si—OH groups are known as Bransted acids. On the other hand, the amide carbonyl groups are... 

Hie basic reaction is the condensation of a bisorthodiamine with a bisethane-dione (Fig. 5.38). The first papers described the unsubstituted quinoxalines,161 but die phenylquinoxalines described later162 are more stable against oxydative... 

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