Hydration of unsaturated

In contrast, the acid-catalyzed hydration of arylbenzoylacetylenes differs markedly from the hydration of a-unsaturated ketones. Hydration of unsaturated ketones has been shown to proceed via a 1,4-addition mechanism where protonation occurs on oxygen to give an oxonium salt, followed by attack of water at the 0-carbon to give a hydroxy enol. The rate-limiting step has been shown to be the protonation of the hydroxy enol (27) ... 

Specific acid Inversion of cane sugar Hydrolysis of acetals Hydration of unsaturated aldehydes C12H22O11 +h2o = c6h12o6 +c6h12o6 R CH(OR2)2 + H20 = R CHO+ 2R2OH CH2 CH CH0 + H20 = CH20H CH2 CHO... 

Figure VIII shows the enantiomeric composition of various hydroxy- and acetoxyacid esters and of if -hexa-and -octalactone isolated from pineapple. Methyl 3-hydroxyhexanoate and methyl 3-acetoxyhexanoate are mainly of the (S)-configuration corresponding to intermediates of B-oxidation. The optical purity of the 5-acetoxy esters is lower than of the 3-acetoxy derivatives. The lactones were mainly of the (R)-configuration. Figure IX presents a possible pathway to explain the formation of these compounds. Methyl (S)-(+)-3-hydroxyhexanoate and methyl (S)-3-acetoxyhexanoate may be derived from (S)-3-hydroxyhexanoyl-CoA by transacylation with methanol and acetyl-CoA, respectively. The biosynthesis of 5-hydroxyacids is still unknown, but they may be formed by elongation of 3-hydroxyacids with malonyl-ACP. This hypothesis could explain their varying enantiomeric composition relative to the 3-hydroxyacids. However, hydration of unsaturated acids and/or the reduction of 5-oxoacids may be involved.

Enoyl-CoA hydratase catalyses the hydration of unsaturated acyl-CoA. This enzyme has broad specificity and can act on a-, P- (or A -) unsaturated CoA in trans or cis configuration. The products formed are... 

From a historical point of view, the earliest work followed some studies on the hydration of unsaturated compounds u> by Lucas et al. 12L They were able to study the following reaction ... 

Microbial hydration of unsaturated fatty acid was first reported by Wallen et al. (4) from our laboratories. They found that a Pseudomonad isolated from fatty material... 

Colloidal copper, prepared by borohydride reduction of copper(II) salts in the presence of protective polymers and with particle sizes of 5.0-15.0 nm (depending on preparation details), is an active catalyst for the hydration of unsaturated nitriles to their corresponding unsaturated amides with 100% selectivity. [53, 268] The copper particle size was unaffected by the catalytic process. The catidyst performance was optimized in a detailed study of the effects of polymer molecular weight, polymer/metal ratio, and the chemical constitution of the polymer. [268, 269]... 

Catalytic hydration of unsaturated bonds is to a certain extent a complementary process to Wacker-type oxidation. Hydration catalyzed by transition-metal complexes has been rather little studied [185]. One process involving hydration and having a good industrial perspective is the telomerization of unsaturated compounds. For example, the aqueous telomerization of butadiene can afford octadienols. The process may be performed in a micellar system in the presence of surfactants with remarkable selectivity [186] ... 

Hydration.—Pseudomonas species of bacteria effect the stereospedfic hydration of unsaturated acids, acting on the following substrate acids to give, in 20—40% yield, the product indicated in parentheses oleic (lOo-hydroxy-stearic acid), linoleic (10D-hydroxyoctadec-c -12-enoic acid), linolenic... 

Fig. 4 Enzymatic hydration of unsaturated fatty acids to produce hydroxystearic acid, a precursor of Y-dodecalactone...

REGIO- AND STEREOSELECTIVE HYDRATION OF UNSATURATED FATTY ACIDS... 

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