Alcoholysis-hydrolysis reaction

It is possible to increase the hydroxyl number by developing an alcoholysis - hydrolysis reaction. 

Tetrachlorosilane was added to aqueous ethanol (the presence of water was accidental). There was no proper stirring during this operation, which led to the formation of two liquid layers of compounds that did not react. The very fast and exothermic reaction of the alcoholysis-hydrolysis of chlorosilane started violently and the large compoundion of hydrogen chloride caused the reactor to detonate. 

Biphasic systems have been effectively used in several enzyme-catalyzed reactions, including peptide and alkyl glycosides synthesis, esterification and transesterification, alcoholysis, hydrolysis, and enantiomeric resolution [2, 24, 60]. Although application of this particular bioconversion system has been used for final products, it is mostly used in the production of intermediate compounds, particularly optically active ones, that can be used as building blocks in the pharmaceutical and food sectors [61-64]. Updated reviews have addressed this matter [2, 4, 24, 60-63], and examples of some representative recent applications of this methodology are given in Table 8.1). 

Since our earlier work gave little insight into the nature of the transition state of our proposed mechanism, the work reported in this paper intends to fill that gap. By attaching a phenyl group to the silicon and varying its electronic character with substituents, we can observe the influence of different partial charges on the silicon. This was done for both the alcoholysis and the hydrolysis reactions. 

The substituent effects for the alcoholysis and hydrolysis reactions of para-substituted phenyldimethylethoxysilanes have been investigated. Compounds with the general formula p-XCf,H4(CH3)2SiOC2H5 were used, where X = H, CH3,... 

Nesmeyanov et al. 201-211) have carried out a systematic study of cyclopentadienyl ligand substitution in bis- and mono-cyclopentadienyl derivatives of titanium, including alcoholysis, hydrolysis, and reaction with FeClj. 

Q-phenyl phosphorochloridothioate (252) were each obtained when (248) was acted upon by PCl here, inversion still predominated although the extent of racemization was greater than that found for the alcoholysis and hydrolysis reactions. The displacements were considered in terms of pentacoordinate intermediates. 

The hydrolysis reaction (eq 4) replaces alkoxide groups with hydroxyl groups. Subsequent condensation reactions involving the silanol groups produce siloxane bonds plus the by-products alcohol (eq 5) or water (eq 6). The reverse of hydrolysis is esterification, in which hydroxyl groups are replaced with alkoxides. The reverse of condensation is siloxane bond alcoholysis (eq 5) or hydrolysis (eq 6). 

Introduction.—Few reviews have appeared dealing with more or less general aspects of cyclophosphazene chemistry. The role of cyclophosphazenes as model compounds for reactions of their polymeric analogues has been discussed some fundamental subjects in the area of phosphorus-nitrogen chemistry such as aminolysis, alcoholysis, hydrolysis, and tautomerization phenomena have also been discussed. An extensive review has appeared dealing with reactions of phosphazenes with alkoxides and aryloxides. ... 

The physiochemical properties of metal alkoxides can be explained with the help of inductive and steric effects, degree of polymerization, volatility as well as the alcoholysis and hydrolysis reactions which help in structural elucidation [18-61]. 

Hydroxide ion promotes only hydrolysis reactions alkoxide ion promotes only alcoholysis reactions. 

C. antarctica lipase catalyzes alcoholysis, ammonolysis (shown in Figure 3.23) [4a], and hydrolysis reactions in the ionic liquids l-butyl-3-methylimidazolium tetrafluoroborate or hexafluorophosphate. Reaction rates were generally same as or better than those observed in organic media. For example, the direct reaction of octanoic add and ammonia was catalyzed by Novozym 435 by bubbling ammonia through a suspension in an ionic liquid. A quantitative conversion was obtained after 4 days. 

Adiponitrile undergoes the typical nitrile reactions, eg, hydrolysis to adipamide and adipic acid and alcoholysis to substituted amides and esters. The most important industrial reaction is the catalytic hydrogenation to hexamethylenediarnine. A variety of catalysts are used for this reduction including cobalt—nickel (46), cobalt manganese (47), cobalt boride (48), copper cobalt (49), and iron oxide (50), and Raney nickel (51). An extensive review on the hydrogenation of nitriles has been recendy pubUshed (10). 

Either acid or base catalysis may be employed. Alkaline catalysts such as caustic soda or sodium methoxide give more rapid alcoholysis. With alkaline catalysts, increasing catalyst concentration, usually less than 1% in the case of sodium methoxide, will result in decreasing residual acetate content and this phenomenon is used as a method of controlling the degree of alcoholysis. Variations in reaction time provide only a secondary means of controlling the reaction. At 60°C the reaction may takes less than an hour but at 20°C complete hydrolysis may take up to 8 hours. 

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