Acetate overoxidation

The growth of Acetobacter species on ethanol results in the accumulation of acetate, which is then completely oxidized by the phenomenon termed acetate overoxidation. The sequential oxidation of ethanol and acetate leads to a diauxic growth profile that is characterized by acetate accumulation in the first exponential growth phase and complete oxidation of the accumulated acetate in the secrnid exponential phase (Saeki et al. 1997). However, in some conditions, ethanol is oxidized to acetate both in the periplasm, by membrane-bound PQQ-dependent ADH and aldehyde dehydrogenase (ALDH), and in the cytoplasm, by soluble NAD (P) -dependent ADH and ALDH. These conditimis are unfavorable for vinegar production because acetate generated in the cytoplasm tends to be rapidly metabolized via the tricarboxylic acid (TCA) cycle. 

Another convenient method for the preparation of tertiary enamines involves the dehydrogenation of saturated bases with mercuric acetate (111-116). A trans-1,2 elimination occurs, which requires an antiperi-planar position of the nitrogen-free electron pair and the eliminated atom. A preferential elimination of the hydrogen atom from the tertiary carbon atom is supposed. Overoxidation can be avoided by adding disodium ethyl-enediaminotetraacetate to the reaction mixture (117). 

Lowering the temperature of the reaction would certainly decrease the rate of acetal hydrolysis and thereby partially remove one of the causes of overoxidation. This would simultaneously decrease the rate of oxidation by periodate. Although no comprehensive study of the effect of temperature on oxidation rates has been made, the number of reactions successfully dealt with in the temperature range of 0 to 6°31 39 78 113 126 130 i33, i64, us, 203,210,266,267 indicates that lowered temperatures do not affect the rates unfavorably. In order to obtain the maximum of selective oxidation and the minimum of overoxidation, periodate oxidations should be performed at as low a temperature as is practicable in relation to the solvent system used and the solubility of the reactants therein. 

Izumi and Urabe [105] found first that POM compounds could be entrapped strongly on active carbons. The supported POMs catalyzed etherization of ferf-butanol and n-butanol, esterification of acetic acid with ethanol, alkylation of benzene, and dehydration of 2-propanol [105], In 1991, Neumann and Levin [108] reported the oxidation of benzylic alcohols and amines catalyzed by the neutral salt of Na5[PV2Mo10O40] impregnated on active carbon. Benzyl alcohols were oxidized efficiently to the corresponding benzaldehydes without overoxidation ... 

Oxidation of Bis (1-methyl-2-acetoxypropyl) selenide with Peracetic Acid. The oxidation of the selenide was conducted in a 10 wt. % solution in glacial acetic acid at 5°C. Peracetic acid was added dropwise as a 1M solution in acetic acid. To prevent any potential overoxidation of the selenide, only 0.3 mole of peracetic acid per mole of selenide was used. 

A -chlorotriazole, dinitrogen tetroxide, chromic acid, chromium trioxide/ A -arylsulfonyl oxaziridines, azaaromatic A -oxides, and aryldimethylamine oxides. Overoxidation to the sulfone, which is a complication with hydrogen peroxide and the peracids, may be minimized by use of only one equivalent of oxidant and low temperatures. Sodium metaperiodate, m-chloro-perbenzoic acid, and hydrogen peroxide in acetone are often the oxidants of choice when the convenient hydrogen peroxide-acetic acid method is unsatisfactory. When particularly mild conditions (CHCI3, 25°) are desired, the oxaziridines may be useful (no acids or bases are present). 

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