Acid/base characteristics

Lysine and aspartic acids are two of the amino acids found in proteins. Describe the acid-base characteristics of these compounds. 

An easy way to quantify the adsorptive and acid/base characteristics of a column is to measure the peak height as a percentage of that expected for complete and undisturbed elution. The two alkanes and three fatty acid methyl esters (non-adsorbing peaks) are connected at their apexes to provide the 100% line as shown in Figure 2.8 [190]. The column activity is then quantified... 

The only means by which inorganic wastes can be rendered nonhazardous are dilution, isolation (as in deep-well injection), in some cases changes in oxidation state, and neutralization. Acidic wastes made up one-fifth of the injected waste volume and involved one-third of the injection wells in 1983. Most of the volume was from inorganic acids (hydrochloric, sulfuric, and nitric). Acid-base characteristics and neutralization were discussed in detail earlier, so the remainder of this section will focus on heavy metals and other hazardous inorganics (selenium and cyanide). 

Absorption from the GI tract is controlled by a variety of factors. These include the acid-base characteristics of the chemical (called the pKa), the solubility, the nature of the delivery (e.g., diet vs. gavage), the nature of any vehicle (suspensions vs. solution, or aqueous vs. nonaqueous), and the gastrointestinal tract of the species under study. 

Extensive tabulations on experimentally determined surface equilibrium constants (Schindler and Stumm, 1987 Dzombak and Morel, 1990) reflecting the acid-base characteristic of surface hydroxyl groups and the stability of surface metal com-... 

In summary, the model proposed on the basis of acid-base characteristics of kaolinite platelets explains the pH-dependent charge primarily to the protonation of the hydroxyl groups at the basal gibbsite and the edge surface. We will later illustrate how this charge characteristics (surface protonation) influences the reactivity (dissolution characteristics) of kaolinite. 

All studies show the zwitterionic nature of the spiropyran merocyanine beyond any doubt and we can further see how the acid-base characteristics of the C9 oxygen and indoline nitrogen are delocalized as alternating charges on the methine bridge, leading to the labile properties of the bridge itself. 

Aramendia et al. (22) investigated three separate organic test reactions such as, 1-phenyl ethanol, 2-propanol, and 2-methyl-3-butyn-2-ol (MBOH) on acid-base oxide catalysts. They reached the same conclusions about the acid-base characteristics of the samples with each of the three reactions. However, they concluded that notwithstanding the greater complexity in the reactivity of MBOH, the fact that the different products could be unequivocally related to a given type of active site makes MBOH a preferred test reactant. Unfortunately, an important drawback of the decomposition of this alcohol is that these reactions suffer from a strong deactivation caused by the formation of heavy products by aldolization of the ketone (22) and polymerization of acetylene (95). The occurrence of this reaction can certainly complicate the comparison of basic catalysts that have different intrinsic rates of the test reaction and the reaction causing catalyst decay. 

Isomerization of jS-isophorone to a-isophorone has been represented as a model reaction for the characterization of solid bases 106,107). The reaction involves the loss of a hydrogen atom from the position a to the carbonyl group, giving an allylic carbanion stabilized by conjugation, which can isomerize to a species corresponding to the carbanion of a-isophorone (Scheme 9). In this reaction, zero-order kinetics has been observed at 308 K for many bases, and consequently the initial rate of the reaction is equal to the rate constant. The rate of isomerization has been used to measure the total number of active sites on a series of solid bases. Figueras et al. (106,107) showed that the number of basic sites determined by CO2 adsorption on various calcined double-layered hydroxides was proportional to the rate constants for S-isophorone isomerization (Fig. 3), confirming that the reaction can be used as a useful tool for the determination of acid-base characteristics of oxide catalysts. 

Each of the three definitions expands our concept of acids and bases. Arrhenius basic definition is adequate for understanding many of the properties of acids and bases. It is important to recognize, though, that acids and bases are not fixed labels that can be applied to a substance. Bronsted-Lowry and Lewis showed that acid-base characteristics are dependent on the reactions that take place between substances. A... 

Fluxes vary in characteristics such as degree of covalency, acid-base characteristics and redox behavior. While chemical reasoning may provide some insights into appropriate choices of suitable fluxes, an empirical approach to the problem is usually necessary to produce crystals of a new compound. 

Lately the most frequently used technique for the determination of thermodynamic and acid/base characteristics is inverse gas chromatography [30,73-75]. In IGC the unknown filler or fiber surface is characterized by compounds, usually solvents, of known properties. IGC measurements can be carried out in two different ways. In the most often applied linear, or ideal, IGC infinite concentrations of n-alkane are injected into the column containing the filler to be characterized. The net retention volume (V ) can be calculated by ... 

Acid-base characteristics of silane-treated E glass fiber surfaces... 

Niederer [100] used ion trap mass spectrometry and negative ion chemical ionisation to determine nitro- and oxypolyaromatic hydrocarbons in soils. Meyer et al. [101] have described a simple and reproducible method which provides the simultaneous determination of polycyclic aromatic hydrocarbons and het-eropolycyclic aromatic hydrocarbons (N, S, O) and their metabolites in contaminated soils. Contaminants extracted from the soil sample were separated by polarity and acid-base characteristics using solid-phase extraction on silica gel and a strong basic anion exchange material. A subfraction containing PANHs and neutral metabolites was subsequently fractionated into neutral and basic... 

Tetrazoles, compared with the other azoles, possess an abnormally high acidity and very weak basicity. Nowadays, a sufficiently large experimental and theoretical database covers the acid-base characteristics of tetrazoles. Not only have dozens of fundamental constants inherent to the compounds of this series been determined by various methods, but also the effect of different factors on these constants has been analyzed. 

To synthesize coordination compounds of definite type, the following properties of a solvent should be taken into account, additionally to its capacity to dissolve ligands and metal sources physical properties (mainly dielectric constant, dipole moment, boiling and melting points) and chemical ones (solvation activity, including acid-base characteristics, specific interaction) [208,222-229],... 

Effect by which all acids stronger than the acid that is characteristic of the solvent react with solvent to produce that acid similar statement applies to bases. The strongest acid (base) that can exist in a given solvent is the acid (base) characteristic of the solvent. 

Liu, R., and H. Tang. 2002. Surface acid-base characteristics of natural manganese mineral particles. Coll. Surf. A, 197 47-54. 

Liu, W. et al., A comparative study of surface acid-base characteristics of natural illites from different origins, J. Colloid Interface Sci., 219, 48, 1999. 

Acid-Base Characteristics of Common Chemical Species... 

Table 2.1. Contribution of cations and anions to the acid/base characteristics of aqueous solutions...

The goal of the present monograph is to generalize the works carried out in this research direction. The subject of investigations is the synthesis of complex oxides of the elements ofl-Vin groups of the Periodic Table from ordinary hydroxides. For numerous hydroxides, substantial differences in their properties are observed, in particular, the differences in acid-base characteristics due to the structure of electron shells of atoms and the nature of chemical bonds. This allows one to search the definite laws governing the formation of complex oxides, and to look for correlation between the structure of initial hydroxides, their thermodynamic parameters and kinetics of mechanochemical synthesis. 

There were some attempts to estimate acid-base properties for oxide compounds, both solids and melts. The most popular of them is Lux-Flood s acid-base theory.2,3 This concept seems to be more effective for estimating the acid-base characteristics of anhydrous borates and of some promising solvents for the flux growth of borate crystals. According to Lewis-Lux s equation,... 

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