Carboxylic acids functional groups

Ammo acids undergo reactions characteristic of both their amine and carboxylic acid functional groups Acylation is a typical reaction of the ammo group... 

Carboxylic Acid Functional Group Reactions. Polymerization is avoided by conducting the desired reaction under mild conditions and in the presence of polymeriza tion inhibitors. AcryUc acid undergoes the reactions of carboxyUc acids and can be easily converted to salts, acryhc anhydride, acryloyl chloride, and esters (16—17). 

However, certain additives can decrease the rate of thermal decomposition [28]. These additives include cyclic sulfates, sulfones, sultones, aliphatic and aromatic anhydrides, and polymers with pendant carboxylic acid functional groups. Most of these materials are latent acids, which decompose on heating in the presence of moisture to form a strong acid, as shown for cyclic sulfate, 9, in Eq. 5. 

Our molecular inset shows citric acid, which has three carboxylic acid functional groups. Citric acid is present in all citrus fruits as well as many other tart-tasting foods, including berries, pineapples, pears, and tomatoes. Lemons are acidic because they contain as much as 3% citric acid by mass. 

One fact to keep in mind with such phases is that weak acid cation-exchange materials based on carboxylic acid functional groups are subject to esterification in the presence of alcohol containing eluents. Even thongh typical eluent conditions (i.e., weakly acidic aqneous eluents containing alcohol) do not favor ester formation, such stationary phases typically exhibit slowly declining capacity when operated in the presence of alcohol-containing eluents. Consequently, such columns are normally operated with acetonitrile, tetrahydrofuran or acetone rather than with methanol, in order to avoid this problem. 

Amino acid a compound possessing both amino and carboxylic acid functional groups. 

The main fluorescent pH indicator probes are based on fluorescein and therefore it is important to understand the pH-dependent ionic equilibria of it and its derivatives, hi aqueous solutions above pH 9 the phenolic and carboxylic acid functional groups in the molecule are almost totally ionised (Figure 3.14). Upon acidification of the dianion, firstly, protonation of the phenolic group occurs (pK 6.4) to yield the monoanion followed by the carboxylic acid (pA < 5), giving the neutral species of fluorescein. On further acidification the fluorescein cation pK 2.1) is generated. In strongly acidic environments fluorescein is non-fluorescent, only the mono-anion and di-anions are fluorescent, with quantum yields of 0.37 and 0.93, respectively. The pH-dependent absorption spectrum of fluorescein exhibits a blue-shift and... 

There is no obvious best solution to these problems. One direction is to redefine (or generalize) the bond separation reaction such that the products are not restricted to the smallest (two-heavy-atom) molecules, but rather include molecules made up of larger components as well (functional groups, rings, etc.). For example, were the phenyl ring and the carboxylic acid functional group included as fragments , then the bond separation reaction for w-toluic acid could be written. 

Amines are nitrogen-containing compounds found in all meteorites that contain amino acids. Their abundances are comparable to those of amino acids, and abundances decrease with increasing numbers of carbon atoms. Similarities between amines and amino acids in the same meteorite have led to the suggestion that amines formed from the amino acids by decarboxylation (loss of the carboxylic acid functional group). This process commonly occurs on heating. 

Uronic acids are monosaccharides in which the terminal primary alcohol group is oxidized to a carboxylic acid functional group, eg, D-glucuronic acid [6556-12-3] (11). 

Since both hydrolysis and acylation yield the release of carboxylic acid functional groups, the medium becomes acidic during the course of the reaction. This requires either the presence of a strongly buffered environment to maintain the pH or periodic monitoring and adjustment of the pH with base as the reaction progresses. 

Because the anhydride is cyclic, its structural units are not incorporated into a ketone and a carboxylic acid as two separate product molecules. Rather, they become part of a four-carbon unit attached to benzene by a ketone carbonyl. The acyl substituent terminates in a carboxylic acid functional group. 

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