Hydrolysis and Solvolysis

Miscellaneous kinetic studies of solvolysis in binary aqueous mixtures have included those of the [Co(NH3)5(dmso)] + cation in seventy-one such mixtures, of the /rans-[Co(dmgH)2Cl(N02)] anion and its methylglyoximate analogue in ethanol- and propan-2-ol-water, of [Cr(sal)3] and of ajffy5-tetra-(p-sulphonato-phenyl)porphineiron(m) in ethanol-water, of the 5,6-dimethylbenzimidazoIe derivative of methylcobalamin, of the acid-catalysed hydrolysis of (BHJ- in acetonitrile containing small amounts of water, and of the rate-determining aquation prior to redox of the [Mn(ox)2(OH2)a] anion in aqueous dimethylformamide. A kinetic study of the reaction of thallium(m) with dimethylformamide indicates caution in the use of this co-solvent in binary aqueous mixtures at elevated temperatures or in the presence of oxidants.  

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The technical advantages of the chemical recycling of PETP bottles are discussed, and some developments in depolymerisation processes are examined. Particular attention is paid to glycolysis, hydrolysis and solvolysis processes respectively developed by TBl, Tredi and Eastman Chemical. 

Hydrolysis and solvolysis of the product formed from the pyrido[l,2-a]-pyrimidine (63) with benzenediazonium chloride was studied by Snyder and Robison.253,254 Ring opening of 63 to give malonamides on the action of aromatic amines was also observed.255... 

IV. Micelle Catalysis of Hydrolysis and Solvolysis A. Carboxylic Esters... 

The hydrolysis and solvolysis of esters can occur through acid-catalyzed, pH-independent, and base-catalyzed mechanisms. These reactions can be classified further according to the type of bond fission and the molecularity of the rate determining step. It is important to realize, however, that there are borderline cases in which classification of the molecularity of the reaction is merely a matter of its academic... 

Hydrolysis and Solvolysis of Sulfates and Phosphates in Micellar Systems... 

The sialic acid structure incorporates a carboxylate at the anomeric centre, which can be inductively electron donating in its deprotonated form and inductively electron withdrawing when protonated, as well as deoxygenation of the position next to the anomeric centre. These features make sialosyl cations more stable than simple aldopyranosyl cations, and hydrolysis and solvolysis reactions have been investigated using the substrates shown in Figure 3.24. 

Recent developments in the understanding of the mechanisms of metal-catalysed (La " ", Pd " ", Cu ", Zn +) hydrolysis (and solvolysis in MeOH) of thiophosphates containing a sulfur atom in the bridging and/or in the non-bridging position were reviewed. ... 

Reaction of hexachloroplatinate(IV) with bromine trifluoride gives a number of ternary complexes [PtCl F. ] ", whose cis/trans geometries are determined (see Scheme 2) by the stronger trans effect of chloride. Qualitative investigations of hydrolysis and solvolysis (in isopropanol of [PtClg] " have probed the effects of added anion nature and the balance between substitution and reduction. Decomposition kinetics of [PtCl5Me] " in alkali halide solutions indicate that the rate-limiting step in the overall reductive elimination process is initial nucleophilic attack by the added halide... 

Surfactants have also been of interest for their ability to support reactions in normally inhospitable environments. Reactions such as hydrolysis, aminolysis, solvolysis, and, in inorganic chemistry, of aquation of complex ions, may be retarded, accelerated, or differently sensitive to catalysts relative to the behavior in ordinary solutions (see Refs. 205 and 206 for reviews). The acid-base chemistry in micellar solutions has been investigated by Drummond and co-workers [207]. A useful model has been the pseudophase model [206-209] in which reactants are either in solution or solubilized in micelles and partition between the two as though two distinct phases were involved. In inverse micelles in nonpolar media, water is concentrated in the micellar core and reactions in the micelle may be greatly accelerated [206, 210]. The confining environment of a solubilized reactant may lead to stereochemical consequences as in photodimerization reactions in micelles [211] or vesicles [212] or in the generation of radical pairs [213]. 

Water hydroly2es pure diketene only slowly to give acetoacetic acid [541-50-4] which quickly decomposes to acetone and carbon dioxide, but increasing the pH or adding catalysts (amines, palladium compounds) increases the rate of hydrolysis. The solvolysis of diketene in ammonia results in aceto acetamide [5977-14-0] if used in stoichiometric amounts (99), and P-arninocrotonarnide [15846-25-0] if used in excess (100). 

This group is more labile to hydrolysis than the TBDMS group and has been used to protect in alcohol where the TBDMS group was too resistant to cleavage. The DEIPS group is approximately 90 times more stable than the TMS group to acid hydrolysis and 600 times more stable than the TMS group to base-catalyzed solvolysis. 

Glycosyl fluorides generally resist hydrolysis (or solvolysis) under basic conditions. For example, 150,151 (see Section 11,3 and Table II), and the deprotected product (153) from 151 were unreactive to sodium methox-ide in refluxing methanol (overnight), only 152 giving the correspond-... 

The diaqua form of czs-DDP can be easily obtained from the dichloro compound by using Aq+, whereas the corresponding trans-DDP derivative requires more forcing conditions [15]. Neither of these species have been isolated, however. Various procedures have been employed to obtain solutions of the first hydrolysis or solvolysis product of czs-DDP and related compounds including chromatographic methods [15] and treatment of the dichloro compound [16] with 1 equiv Aq+ in DMF. With trans-DDP, controlled hydrolysis of the parent compound in basic solution gives trans-[PtCl(OH)(NH3)2]-H20 and trans-[Pt(OH)2(NH3)2] ... 

N-Hydroxy-N-nitrosamines with an aliphatic group at O2 produce a compound stable to aqueous acid and base (Fig. 3.4, 29) [158], whereas all other N-hydroxy-N-nitrosamines are susceptible to hydrolysis and appropriate 02-derivatives also render these materials vulnerable. The hydrolysis endpoint is the formation of nitroxyl (HNO) [which dimerizes to form nitrous oxide (N20)] and a C-nitroso compound. These products are formed from aryl [159] and alkyl bound unsubstituted diazenium-diolates as well as Oralkylated derivatives [160]. Studies of the solvolysis of Oi-alkyl derivatives are complicated by their tendency to decompose via competing radical pathways [161], but the Oi-benzyl derivatives are unique in that they hydrolyze back to the original synthetic precursors (Scheme 3.14) [162]. 

DinitrobenzenesuIfenic esters were proposed as protecting groups for carboxyl groups.The solvolysis of only a small variety of esters was studied with a high-pressure mercury lamp, and the yields were 88-98% (see Scheme 26). It should be noted, however, that the group is particularly sensitive to hydrolysis and ammonolysis. 

Proton transfer may proceed directly or via a six-membered cyclic transition state involving a molecule of water. A calculation of the intermediate zwitter-ionic concentration for the hydrolysis of methyl phosphate monoanion, based on the pKa values for methanol and methyl phosphate dianion, predicts the first-order rate coefficient for zwitterion decomposition to be ca. 10 sec-1 at 100°C. This value is in good agreement with the observed rate of hydrolysis and, considering the assumptions involved, with the rate of P-O bond fission of the presumed zwitterionic intermediate (2) formed in the Hg(II) catalyzed solvolysis of phosphoenolpyruvic acid, a model reaction for pyruvate kinase10. 

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