Ester exchange reaction

Catalytic amounts of mercuric chloride are usually employed in this preparation. Aluminum isopropoxide is a useful Meerwein-Potmdorf-Verley reducing agent in certain ester-exchange reactions and is a precursor for aluminum glycinate, a buffering agent (see Alkoxides, metal). 

The equation for the ester-exchange reaction (1) is shown in Figure 20.3. 

In recent years, however, the ester exchange reaction has been decreasingly used, with manufacturers now usually preferring to use direct acid glycol condensation with purified terephthalic acid. 

Rolgamidine (14) is a dihydropyrrole derivative which has antidiarrheal activity It can be synthesized by alkylation of trans 2,5-dimethyl-3 pyrroline (12) with methyl bromoacefate to give 13 An amide-ester exchange reaction with guanidine hydrochloride completes the synthesis of rolgamidine (14) [3]... 

Reverse ester exchange reaction, 20 44 Reverse flow, cake dislodging by,... 

With regards to the crystallization behavior of these copolyesters(Figures 3 and 5), a single melting peak indicative of a PLLA crystalline phase is seen. The fact that the PCL phase does not exhibit the ability to crystallize following the polymerization of LLA may be attributed to the occurrence of ester exchange reactions that limit the average sequence... 

A number of studies have been carried out on the ligand reactivities of the metal complexes of Schiff bases derived from amino acid esters and carbonyl compounds. Ester exchange reactions were first reported by Pfeiffer et a/.492 and extended by other investigators.493 496... 

Copper(II) complexes of the Schiff bases derived for salicylaldehyde and dibenzyl asparate or glutamate have recently been characterized.497 Refluxing these complexes in methanol for 30 min gives bis(a-methyl-/3-benzyl-N-salicylideneaspartato)copper(II) in which selective ester and bis(a-methyl-y-benzyl-N-salicylideneglutamato)copper(II) exchange occurs. A similar selective ester exchange reaction has also been observed with the copper(II) complex of the Schiff base derived from salicylaldehyde and dibenzyl dl-asparate.498... 

The ester exchange reactions of the oxyphosphoranes (285 R = R = Ph, Me, 4-nitrophenyl) with several alcohols, models for nucleosides, have been investigated.252 The oxidative hydrolysis of the phosphorus(V) esters of thiols such as (286)-(289) with... 

The hydrolysis reactions of A -phospho amino acids seen as models for protein dephosphorylation have been studied in Tris-HCl buffer (pH7.5)-DMSO. The reactions were first order and the rates were very much faster than those of simple phosphoamidates. A pentacoordinated phosphorus intermediate is proposed on the reaction pathway.265 The rates of ester exchange reactions of alcohols (nucleoside models) with the oxyphosphorane (299) have been studied and the rates of exchange are much faster for diols than for mono-alcohols.266... 

The Grignard reaction has been improved by the use of phenyl diethyl orthoformate, which may be prepared by an ester exchange reaction between equimolar amounts of triethyl orthoformate and phenol.113... 

Transesterification [236] and the ester exchange reaction [237] were reported to be efficiently catalyzed (Eqs. 30 and 31). Either of the exchange reactions are sensitive to steric constraints of the substrates and to metal ion size. For example, transesterification is most applicable to primary alcohols. Increased catalytic activity in the presence of larger lanthanide centers is explained by enhanced coordinative unsaturation and increased basicity of the alkoxide complexes. Strong basicity of the lanthanide isopropoxides is considered to catalyze effectively the transhydrocyanation from acetone cyanohydrin to sev-... 

If we carry out an ester exchange reaction on a one molar solution of MeCC R2 in an alcohol R]OH as solvent with catalytic R1 - and let the mixture reach equilibrium, what will be the equilibrium composition if the solvent alcohol R H is, say, 25M in itself ... 

The product is a thiol ester and so can exchange with Co ASH in a simple ester exchange reaction. This is a nucleophilic attack on the carbonyl group and will release the reduced form of lipoic acid. All that is necessary to complete the cycle is the oxidation of the dithiol back to the disulfide. This is such an easy reaction to do that it would occur in air anyway but it is carried out in nature by FAD, a close relative of NAD+. 

Symmetrical secondary alcohols are prepared by this method from ethyl formate and organomagnesium halides. Excellent directions are available for 3-pentanol (70%) and 5-nonanol (85%). An ester exchange reaction sometimes gives the formate of the alcohol as an impurity in the... 

Ester formation occurs with complete stoichiometric conversion at relatively low reaction rates (t./, 100-600 s). In the absence of water no back reaction takes place. There is a very slow ester-ester exchange reaction ty, k 5000 s). The boronic ester moieties can be readily cleaved in water/alcohol. This reaction is, in principle, fast and complete (t./, 100 s), so that the template can be released from an imprinted macroporous polymer in 85-95% yield. 

Thus PET has been prepared by reaction of DMT and diacetoxyethane. Similarly, polycarbonates have been made from the bis(alkyl carbonates) or bis(aryl carbonates) of bisphenols. No important kinetic studies have been made of the esterolysis (or double ester-exchange) reaction. 

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