Acids, organic hydroxy

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. 

Citric acid undergoes most of the reactions typical of organic hydroxy polycarboxylates. 

In more recent times chemically defined basal media have been elaborated, on which the growth of various lactic acid bacteria is luxuriant and acid production is near-optimal. The proportions of the nutrients in the basal media have been determined which induce maximum sensitivity of the organisms for the test substance and minimize the stimulatory or inhibitory action of other nutrilites introduced with the test sample. Assay conditions have been provided which permit the attainment of satisfactory precision and accuracy in the determination of amino acids. Experimental techniques have been provided which facilitate the microbiological determination of amino acids. On the whole, microbiological procedures now available for the determination of all the amino acids except hydroxy-proline are convenient, reasonably accurate, and applicable to the assay of purified proteins, food, blood, urine, plant products, and other types of biological materials. On the other hand, it is improbable that any microbiological procedure approaches perfection and it is to be expected that old methods will be improved and new ones proposed by the many investigators interested in this problem. 

Nitrosyl perchlorate Organic materials Perchloric acid Alcohols Permanganic acid Organic materials Peroxodisulfuric acid Organic liquids Potassium dioxide Ethanol Potassium perchlorate Ethanol Potassium permanganate Ethanol, etc. Ruthenium(VIII) oxide Organic materials Silver perchlorate Aromatic compounds Sodium peroxide Hydroxy compounds Uranium hexafluoride Aromatic hydrocarbons, etc. Uranyl perchlorate Ethanol See v-halomides Alcohols... 

Zhu, D., Ankati, H., Mukheijee, C. et al. (2007) Asymmetric reduction of /3-ketonitriles with a recombinant carbonyl reductase and enzymatic transformation to optically pure /3-hydroxy carboxylic acids. Organic Letters, 9 (13), 2561-2563. 

In view of these shortcomings, the system has been limited to only three classes of optically active organic compounds, the Sugars, amino acids and hydroxy acids. 

In sludge anionic and non-ionic surfactants carboxylic acids hhydroxybutyrate hydroxy valerate chloroaliphatic compounds chlorophenols polychlorobiphenyls 4-nitrophenol mixtures of organic compounds chlorinated insecticides, phenoxy acetic acid type herbicides and organotin compounds. 

A large variety of organic reagents are naturally available as single enantiomers (e.g., amino acids, carbohydrates, hydroxy acids). Therefore, organic catalysts are generally inexpensive to prepare, easy to handle, and readily accessible in industrial-scale quantities. 

Asymmetric synthesis of cyanohydrins is an important process in organic synthesis because cyanohydrins can be easily converted into a variety of valuable synthetic intermediates such as a-hydroxy acids, a-hydroxy ketones, and g-amino alcohols. 

Zincon (o-[l-(2-hydroxy-5-suIpho)-3-phenyI-5-formazono]-benzoic acid) [135-52-4] M 459.4. Main impurities are inorganic salts which can be removed by treatment with dilute acetic acid. Organic contaminants are removed by refluxing with ether. It can be recrystd from dilute H2SO4. [Fichter and Schiess B 33 751 J900]. 

D-Panthenol (Provitamin B, / -2,4-dihydroxy-3,3-dimethylbutyric acid 3-hydroxy-propylamide) [81-13-0] M 205.3, b 118-120°/0.02mm, d20 1.2, n2D° 1.4935, [a]2D° (c 5, H2O). Purified by distn in vacuo. It is a slightly hygroscopic viscous oil. Soluble in H2O and organic solvent. It is hydrolysed by alkali and strong acid. [Rabin J Amer Parm Assoc (Sci Ed) 37 502 1948 Bonati and Pitre Farmaco Ed Scient 14 43 1959]. 

An asymmetric C-C coupling, one of the most important and challenging problems in synthetic organic chemistry, seems to be most appropriate for the creation of a complete set of diastereomers because of the applicability of a convergent, combinatorial strategy [38-40]. In Nature, such reactions are facilitated by lyases which catalyze the (usually reversible) addition of carbo-nucleophiles to C=0 double bonds, in a manner mechanistically most often categorized as aldol and Claisen additions or acyloin reactions [41], The most frequent reaction type is the aldol reaction, and some 30 lyases of the aldol type ( aldolases ) have been identified so far [42], of which the majority are involved in carbohydrate, amino acid, or hydroxy acid metabolism. This review will focus on the current state of development of this type of enzyme and will outline the scope and limitations for their preparative application in asymmetric synthesis. 

F. S. Brown and C. R. Bury 6 obtained colloidal solutions of phosphorus pentoxide in nitrobenzene by stirring the mixture in the presence of alcohols or organic acids. The hydroxy-compound is absorbed and peptizes the pentoxide. Traces of moisture cause coagulation. Cone. soln. set to gels on keeping. 

The chemistry of silicon oxygen compounds with SiOs and SiC>6 skeletons in aqueous solution is of special interest. It has been speculated that such Si(IV) complexes with ligands derived from organic hydroxy compounds (such as pyrocatechol derivatives, hydroxycarboxylic acids, and carbohydrates) may play a significant role in silicon biochemistry by controlling the transport of silicon. 

Sugar acids, mono-, di-, and tri-carboxylic acids, keto-, hydroxy-acids as well as unsaturated organic acids are present in foods. While uronic acids participate in the browning reaction, others might accelerate or retard the reaction. 

The precipitation of aluminium hydroxide by solutions of sodium hydroxide and ammonia does not take place in the presence of tartaric acid, citric acid, sulphosalicylic acid, malic acid, sugars, and other organic hydroxy compounds, because of the formation of soluble complex salts. These organic substances must therefore be decomposed by gentle ignition or by evaporating with concentrated sulphuric or nitric acid before aluminium can be precipitated in the ordinary course of qualitative analysis. 

Optically active cyanohydrins are synthetic precursors of a-hydroxy carboxylic acids, a-amino carboxylic acids, /1-hydroxy amines, and several other classes of organic compound of biological importance [146]. Several efficient catalysts have been developed by using titanium as the central metal. 

As already noted, the structures of hydroxy-acids, which include B(0H)3 and Te(OH)g, are described in Chapter 14 with hydroxides, to which they are more closely related stmcturally, the molecules being linked by long 0-H—0 bonds (two from each OH) as in many organic hydroxy-compounds. One form of metaboric acid, consisting of cyclic 6303(011)3 molecules, is also of this type, for the three 0 atoms in the ring are not involved in hydrogen bonding. 

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