Glycollic acid. Table

A number of carboxylic acids other than acetic were investigated as solvents or promoters. All of these acids which were stable to reaction conditions were found to be effective in promoting glycol ester production (e.g., propionic, pivalic, benzoic, etc.). However, other Br nsted acids of non-carboxylic nature were not found to be effective promoters. Thus penta-chlorophenol, although it has a pKa value (4.82) very close to that of acetic acid (4.76), is not a comparable promoter (Table I, reaction 13). Likewise, phosphoric acid (pK 2.15) is not an effective solvent or co-solvent with acetic acid (Table I, reaction 8). Experiments with lower concentrations of these acids in sulfolane solvent also showed that carboxylic acids are unique in promoting glycol formation. The promoter function of carboxylic acids thus appears not to be dependent (only) upon their acidity, but on some other chemical or structural property. 

The most common synthetic biodegradable polymers for suture material and their corresponding weight loss in aqueous solution are listed in Table 3.10. Of these, poly(glycolic acid), PGA, poly(lactic acid), PLA, and copolymers of these two polyesters are the most widely used for resorbable sutme material. PGA is a tough. 

Table 4 A Partial List of Marketed Drug Delivery Products Utilizing Polylactic Acid or Poly(lactic-co-glycolic) Acid Polymers...

Isbell and co-workers (51) have tried to minimize the oxygen reaction and to maximize the peroxide reaction. When a large excess of peroxide and a low temperature were maintained, they found that the monosaccharides are converted almost quantitatively to formic and two-carbon acids. Table II presents results for the peroxide oxidation of 14 sugars. The total acid produced from aldo-hexoses under favorable conditions is about six moles, consisting almost entirely of formic acid. Aldopentoses react more rapidly than aldo-hexoses and yield about five moles of formic acid per mole of pentose. Fructose and sorbose yield approximately five moles of total acid of which four moles are formic acid. Glycolic acid was identified qualitatively but not determined quantitatively. L-Rham-nose and L-fucose yield about five moles of acid, including four moles of formic acid. Acetic acid was identified only qualitatively. 

A DS of up to 1.0 is obtained in one step by applying optimised reaction conditions 3.8 M aqueous NaOH, reaction temperature of 60 °C for 90 min in tert-butanol/water or isopropanol/water 85 15 (v/v) mixtures (Table 12) [219]. The DS of CMD can be increased by repeated carboxymethy-lations. CMD with DS 1.5 was realised by two-step carboxymethylation. Under optimal conditions, the applied NaOH solution was 3.8 M. The DS value is decreased with lower NaOH concentrations because of incomplete activation of the hydroxyl groups, and also with higher NaOH concentrations due to increasing side reactions of MCA with NaOH forming glycolic acid [280]. 

Two organic acids were selected as test additives for Ca(0H>2, adipic acid because of its extensive use in wet scrubbing, and glycolic acid, because of its deliquescent properties. Both of these acids proved to be detrimental to the reaction of SO2 with Ca(OH>2, as can be seen from Table II. At 74% relative humidity the average Ca(0H)2 conversion in the reactor decreased from 22 to 11% when 5 wt% of glycolic acid was added to the Ca(OH>2, and from 22 to 20% when 1 wt% adipic acid was used as additive. 

Table 6.42 (S)-l-Naphthyl glycolic acid-catalyzed O-nitroso aldol reactions.

On the other hand, Take and Otsuka (27) stated that the aqueous extract of the corbicula, Corbicula leana, was judged more acceptable by testers than that from which the organic acids had been removed by extraction with diethyl ether. They reported that exceedingly large amounts of citric, malic, and glycolic acids and a small amount of succinic acid were contained in their sample. Therefore, the contribution of succinic acid to the taste is obscure. Take and Otsuka noted that a synthetic mixture (Table III) containing amino acids and organic acids in the same relative concentrations as they occurred in the corbicula extract, simulated the taste of the natural extract. 

TABLE 1. Biodegradable poly[(lactic-co-glycolic acid) substrates free radically functionalized with grafted acrylic acid or 2-hydroxylethyl acrylate. 

A few comments on the values of r and (r+ - - r ) (cf. Table VIII) are necessary. Increasing hydrocarbon content decreases the hydrophilic property of the anion (cf. formic, acitic, propanoic, butanoic, 3-methyl-butanoic, and benzoic acids) resulting in the decrease of hydration the trend eventually levels off. Hydrophilic substitution increases hydration (cf. acetic, chloroacetic, cyanoacetic, glycolic acids cf. glutaric, succinic, and malonic acids cf. benzoic and salicyclic acids). Also note that r is smallest for benzoic acid and largest for malonic acid. These trends cannot be fortuitous. 

Co-monomer ratios of lactic acid and glycolic acid for poly(DL-lactide-co-glycolide) range from 85 15 to 50 50. Table I shows the chemical and trade names of different commercially available aliphatic polyesters. 

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