Hydroxy acids formation

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Chiral Lactones and Polyesters. Similar to intermolecular reactions described previously. Upases also catalyze intramolecular acylations of hydroxy acids the reactionsults in the formation of lactones. 

Cyanohydrin Synthesis. Another synthetically useful enzyme that catalyzes carbon—carbon bond formation is oxynitnlase (EC 4.1.2.10). This enzyme catalyzes the addition of cyanides to various aldehydes that may come either in the form of hydrogen cyanide or acetone cyanohydrin (152—158) (Fig. 7). The reaction constitutes a convenient route for the preparation of a-hydroxy acids and P-amino alcohols. Acetone cyanohydrin [75-86-5] can also be used as the cyanide carrier, and is considered to be superior since it does not involve hazardous gaseous HCN and also virtually eliminates the spontaneous nonenzymatic reaction. (R)-oxynitrilase accepts aromatic (97a,b), straight- (97c,e), and branched-chain aUphatic aldehydes, converting them to (R)-cyanohydrins in very good yields and high enantiomeric purity (Table 10). 

Bicucine, C20H19O7N, H2O. This alkaloid has m.. 222° (dec.) and — 115 4° (N/10, KHO) but in N/HCl it shows mutarotation — 145° to — 100°,due to the formation of an equilibrium mixture of bicucine and bicuculline. Alkaline permanganate oxidises it to 3 4-methylene-dioxyphthalic acid, isolated as the ethylimide. In view of its formation from bicuculline by the action of alkali, Manske has suggested for its formula (II) or (III), the former representing it as the nomarceine (p. 208) analogue of bicuculline, whilst (III) makes it the hydroxy-acid corresponding to the lactone, bicuculline and is preferred. 

Mandelic Acid.—The reaction furnishes a simple and general method for obtaining hydroxy-acids from aldehydes or ketones by the aid of the cyanhydrin. The formation of the cyanhydrin may be effected in the manner described or by the action of hydrochloric acid on a mixture of the aldehyde or ketone with potassium cyanide, or, as in the case of the sugais, by the use of liquid hydrocyanic acid and a little amme-nia. 

The rhodium catalyst previously discussed is employed in the hydrogenation of / -hydroxybenzoic acid. The resulting mixture of cis and trans products is separated by virtue of the ready formation of the lactone of the cis product, which is then hydrolized to the hydroxy acid. 

If the hydroxy-acid is heated with hydrobromic acid, it is converted into l-methyl-l-bromocyclohexane-4-carboxylic acid, and this is decomposed by boiling with sodium carbonate with loss of hydrogen bromide and with formation of 1-methyl-A cyclohexene-4-carboxyhc acid—... 

The reaction between acid anhydrides and diols is another convenient method of polyester synthesis. The reaction proceeds in two steps with the formation of an intermediate hydroxy acid (Scheme 2.15). 

Effects of -/-Radiation. Part I. Polymer Formation from Sugars, Hydroxy-acids and Amino-acids. S. A. Barker, P. M. Grant, M. Stacey, and R. B. Ward, J. Chem. Soc., (1959) 2648-2654. 

Lithium enolates of carboxylic acids such as phenylacetic acid or of amides such as N-methyl-N-phenylvaleric acid amide 1974 are oxidized by BTSP 1949 to a-hydroxy acids, which are isolated after esterification, e.g., to 1973, or to a-hydroxyamides such as 1975 [155] (Scheme 12.43) (cf. also the formation of 3-hydroxybutyrolactam 1962). 

In 1929 Carothers proposed a generally useful differentiation between two broad classes of polymers condensation polymers in which the molecular formula of the structural unit (or units) lacks certain atoms present in the monomer from which it is formed, or to which it may be degraded by chemical means, and addition polymers, in which the molecular formula of the structural unit (or units) is identical with that of the monomer from which the polymer is derived. Condensation polymers may be formed from monomers bearing two or more reactive groups of such a character that they may condense intermolecu-larly with the elimination of a by-product, often water. The polyamides and polyesters referred to above afford prime examples of condensation polymers. The formation of a polyester from a suitable hydroxy acid takes place as follows ... 

Polyfunctionality of the reactants is not sufficient in itself to assure formation of polymer the reaction may proceed intramolecularly with the formation of cyclic products. For example, hydroxy acids when heated yield either lactone or linear polymer (or both),... 

The principles set forth above account reasonably well for the course of bifunctional condensations under ordinary conditions and for the relative difficulty of ring formation with units of less than five or more than seven members. They do not explain the formation of cyclic monomers from five-atom units to the total exclusion of linear polymers. Thus 7-hydroxy acids condense exclusively to lactones such as I, 7-amino acids give the lactams II, succinic acid yields the cyclic anhydride III, and ethylene carbonate and ethylene formal occur only in the cyclic forms IV and V. 

Roberts DJ, PM Fedorak, SE Hrudey (1990) COj incorporation and 4-hydroxy-2-methylbenzoic acid formation during anaerobic metabolism of m-cresol by a methanogenic consortium. Appl Environ Microbiol 56 472-478. 

A low-molecular-weight condensation product of hydroxyacetic acid with itself or compounds containing other hydroxy acid, carboxylic acid, or hydroxy-carboxylic acid moieties has been suggested as a fluid loss additive [164]. Production methods of the polymer have been described. The reaction products are ground to 0.1 to 1500 p particle size. The condensation product can be used as a fluid loss material in a hydraulic fracturing process in which the fracturing fluid comprises a hydrolyzable, aqueous gel. The hydroxyacetic acid condensation product hydrolyzes at formation conditions to provide hydroxyacetic acid, which breaks the aqueous gel autocatalytically and eventually provides the restored formation permeability without the need for the separate addition of a gel breaker [315-317,329]. 

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