Carboxyl group, 787 table

A number of the water-soluble polymers also have adhesive properties which are being extensively evaluated for drug delivery (9). These polymers will adhere to the mucous coating in the gastrointestinal tract, the nose, and the mouth to delay passage and sustain drug release. Those polymers with the best adhesive properties are those with hydroxyl and carboxyl groups. Table II lists some of the bioadhesive polymers and their adhesive properties. 

One possibility is hydroxyl endgroups, which may be formed by a side reaction of sulfate ion-radicals to form hydroxyl radicals (9) or hydrolysis of the surface sulfate groups. To determine if hydroxyl groups were present, the ion-exchanged latexes were oxidized by heating with persulfate and 10 silver ion at 90°, then ion exchanged and titrated conductometrically to determine the carboxyl groups. Table II (9) shows that some sul-... 

The hydrophilic groups of anionic surfactants consist in most cases of sulfonate, sulfate, or carboxyl groups (Table 30.1). Amongst them, LAS are produced in the largest quantities worldwide. These are mainly used in powdery and liquid laundry detergents and household cleaners. 

The polarity of a lipid affects its volatility, solubility, and nonspecific binding to other polar compounds. Lipids are often functionally classified as neutral or polar on the basis of their mobility on thin-layer chromatography using a neutral or polar solvent system. Neutral lipids such as wax esters, steryl esters, ether lipids, and TAG are chemically neutral while other neutral lipids, such as free FA, fatty alcohols, and monoacylglycerols, are actually slightly polar due to the presence of hydroxyl or carboxyl groups. Table 3.8 lists the relative polarities of some common lipid classes. 

A selection of important anionic surfactants is displayed in table C2.3.1. Carboxylic acid salts or tire soaps are tire best known anionic surfactants. These materials were originally derived from animal fats by saponification. The ionized carboxyl group provides tire anionic charge. Examples witlr hydrocarbon chains of fewer tlran ten carbon atoms are too soluble and tliose witlr chains longer tlran 20 carbon atoms are too insoluble to be useful in aqueous applications. They may be prepared witlr cations otlrer tlran sodium. 

Systematic names for carboxylic acids are derived by counting the number of car bons m the longest continuous chain that includes the carboxyl group and replacing the e ending of the corresponding alkane by oic acid The first three acids m Table 19 1 methanoic (1 carbon) ethanoic (2 carbons) and octadecanoic acid (18 carbons) illus trate this point When substituents are present their locations are identified by number... 

Table 19 3 lists the ionization constants of some substituted benzoic acids The largest effects are observed when strongly electron withdrawing substituents are ortho to the carboxyl group An o nitro substituent for example increases the acidity of benzoic acid 100 fold Substituent effects are small at positions meta and para to the carboxyl group In those cases the values are clustered m the range 3 5-4 5... 

Glycine is the simplest ammo acid and the only one m Table 27 1 that is achiral The a carbon atom is a chirality center m all the others Configurations m ammo acids are normally specified by the d l notational system All the chiral ammo acids obtained from proteins have the l configuration at their a carbon atom meaning that the amine group IS at the left when a Fischer projection is arranged so the carboxyl group is at the top... 

Many trivial names exist for acids these are listed in Table 1.11. Generally, radicals are formed by replacing -ic acid by -oyL When a trivial name is given to an acyclic monoacid or diacid, the numeral 1 is always given as locant to the carbon atom of a carboxyl group in the acid or to the carbon atom with a free valence in the radical RCO—. 

The method of choice for determining carboxyl groups in lignin is based on potentiometric titration in the presence of an internal standard, /)-hydroxybenzoic acid, using tetra- -butylammonium hydroxide as a titrant (42). The carboxyl contents of different lignins are shown in Table 6. In general, the carboxyl content of lignin increases upon oxidation. 

Decarboxylation of sahcyhc acid takes place with slow heating because of the presence of the electronic configuration of the carboxyl group ortho to the hydroxyl group, but does not occur in the other isomers of hydroxyben2oic acid. On rapid heating, sahcyhc acid sublimes because of its low vapor pressure. This property allows commercial separation from the other isomers as a means of purification analogous to distillation. The differences ia the vapor pressures are shown ia Table 4. 

Aqueous solutions of citric acid make excellent buffer systems when partially neutralized because citric acid is a weak acid and has three carboxyl groups, hence three p-K s. At 20°C pifj = 3.14, pi 2 4.77, and = 6.39 (2). The buffer range for citrate solutions is pH 2.5 to 6.5. Buffer systems can be made using a solution of citric acid and sodium citrate or by neutralizing a solution of citric acid with a base such as sodium hydroxide. In Table 4 stock solutions of 0.1 Af (0.33 N) citric acid are combined with 0.1 Af (0.33 N) sodium citrate to make a typical buffer solution. 

The anomalous effect of the last two rubbers in the table with their low solubility parameters is possibly explained by specific interaction of PVC with carbonyl and carboxyl groups present respectively in the ketone- and fumarate-containing rubbers to give a more than expected measure of compatibility. It is important to note that variation of the monomer ratios in the copolymers and terpolymers by causing changes in the solubility parameter and eompatibility will result in variation in their effect on impact strength. 

Table 7-17. Relative Rates of Intramolecular Catalysis of Ester Hydrolysis by Carboxylate Groups...

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