Esters general cleavage

General Preparation of Esters, 227 General Cleavage of Esters, 229... 

Provided due attention is paid to the potential deprotonation of the substrate, and of the cyclodextrins (VanEtten et al., 1967a,b Gelb et al., 1980, 1982 Tee and Takasaki, 1985), the value of Ks should not be pH dependent. However, for many reactions, such as the widely studied ester cleavage, ku, kc, and k2 are all dependent on the pH of the medium. This makes direct comparisons between the observed constants for different CD-mediated reactions either difficult or problematical. However, in general, the ratios kc/ku and k2/ku are independent of pH and so are more useful for comparative purposes. 

In most cases of ester cleavage by CDs, an anion of the CD functions as a nucleophile (see Scheme 2). However, in a few instances the anion acts as a general base, assisting the attack of a molecule of water (e.g. [28]). 

Calixcrown 5, featuring two diethylaminomethyl side-arms at the polyether bridge, testifies an attempt at a higher order multifunctional catalysis of ester cleavage, namely, from nucleophilic-electrophilic to nucleophilic-electrophilic-general acid catalysis [20]. 

Allyl Ester Cleavage Using Chlorotris(triphenylphoshine)rhodium(I) General Procedure I ... 

AUyl Ester Cleavage Using Dichlorobis(triphenylphosphine)palladium(II) General Procednre P l... 

After drying this block polymer precursor, partial hydrolysis of the methacrylate block lead to the ion containing block copolymer. The hydrolysis route is shown in Scheme II. The hydrolysis method employed utilized potassium superoxide as a general route to ester cleavage to generate in a direct fashion potassium carboxylate units. 

Purified terephthalic acid (PTA) is one of the largest-scale chemicals produced worldwide. Main fields of application for PTA include PET chips, PET films, PET fibers, and bottle resins. Two principal processes are used for the purification of raw terephthalic acid esterification distillation and ester cleavage of dialkyl terephthalates, and direct hydrogenation and crystallization [90]. The latter process was discovered by the Standard Oil Co.and later licensed worldwide, becoming the dominant process for PTA. The general process is to hydrogenate... 

The depolymerization of suberin through ester cleavage is in general a key step both for composition analysis (usually carried out by GC-MS), and to isolate monomers for further chemical transformation. Depending either... 

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