Carboxylic, generally group

The transition state for the rapid hydrolysis of the monoanion has been depicted as involving an intramolecular general acid catalysis by the carboxylic acid group, with participation by the anionic carboxylate group, which becomes bound at the developing electrophilic center... 

Hydrolysis of aspirin in H2 0 leads to no incorporation of into the product salicylic acid, ruling out the anhydride as an intermediate and thereby excluding mechanism 1. The general acid catalysis of mechanism III can be ruled out on the basis of failure of other nucleophiles to show evidence for general acid catalysis by the neighboring carboxylic acid group. Because there is no reason to believe hydroxide should be special in this way, mechanism III is eliminated. Thus, mechanism II, general base catalysis of hydroxide-ion attack, is believed to be the correct description of the hydrolysis of aspirin. 

Methods of synthesis for carboxylic acids include (1) oxidation of alkyl-benzenes, (2) oxidative cleavage of alkenes, (3) oxidation of primary alcohols or aldehydes, (4) hydrolysis of nitriles, and (5) reaction of Grignard reagents with CO2 (carboxylation). General reactions of carboxylic acids include (1) loss of the acidic proton, (2) nucleophilic acyl substitution at the carbonyl group, (3) substitution on the a carbon, and (4) reduction. 

Carboxylates (9.4, where R is the long-chain hydrophobe and X the cation) represent the oldest type of surfactants, since they could be obtained from naturally occurring fats and oils long before the advent of the petrochemical industry sodium heptadecanoate (9.5), for example, incorporates the cetyl group as hydrophobe. Sodium stearate, sodium palmitate and sodium oleate are the simplest carboxylates generally used as surfactants. Alkylaryl compounds (9.6) are also known. 

Esterification reactions are acid catalyzed [18-21], and an overall reaction order of 3 (2 with respect to acid and 1 with respect to alcohol) is generally accepted [9], Thus, the acid behaves both as reactant and as catalyst. It can be assumed that the concentration of acid groups, cacid, is the sum of the concentrations of carboxylic end groups (tTPA) and carboxylic groups of the free acid (TPA). 

In general, the degradation of PET is characterized by a loss in molecular weight, a loss in weight in the case of thermal and thermal oxidative degradation, and an increase in the carboxyl end groups. This is usually accompanied by the material first turning yellow, then brown and finally black [17]. 

The reaction rate is very sensitive to the ratio of hydroxyl to carboxyl end groups, as shown by Figures 4.7 and 4.8. At low carboxyl concentrations, the transesterification reaction will be favoured, while at high carboxyl concentrations the esterification route will be favoured. If the transesterification and esterifications were equal, which they are generally not, then the consumption ratio of end... 

Generally, two to three preheater sections are used for the product heat-up by using nitrogen, and two to three sections are required to reach the final viscosity. Cooling is carried out either in an additional compartment or with a fluid bed. Typically, for a viscosity increase from 0.60 up to 1.0, the crystallinity increases to ca. 62 vol%, and the carboxyl end group concentration decreases by approximately 10-15 mol/t. This equates to both esterification and transesterification contributing half of the IV increase if side reactions are neglected. 

Amino Acids Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins. [NIH]... 

Carboxylic acid groups attached to an aromatic ring are reducible at cathodes of lead or mercury in sulphuric acid [127]. Oxalic acid is also reduced but in general, where the carboxyl group is attached to an aliphatic carbon as in phenylacetic acid... 

Two carboxylic acid groups may combine to form cm acid cmhydride with the general structure shown in Figure 9-7. We discuss this combination in more detail, including synthesis and reactions, in Chapter 12. 

Molecules may contain more than one carboxylic acid group. The dicarboxylic acids,which contain two carboxylic acid groups, are very important in areas such as organic synthesis. Many dicarboxylic acids have the general formula H00C-(CH2) -C00H. Table 12-1 lists how the names of the dicarboxylic acids relate to the value of n. 

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