Acetate methyl group

Investigation has shown that chain transfer to polymer occurs predominantly on the acetate methyl group in preference to the chain backbone one estimate of the magnitude of the predominance is 40-fold (92,93). The number of branches per molecule of poly(vinyl acetate) polymerised at 60°C is ca 3, at 80% conversion. It rises rapidly thereafter and is ca 15 at 95% conversion and 1-2 x lO" number-average degrees of polymerisation. 

Acetals are easily hydrolyzed by dilute acid, but ethers are stable under these conditions. Treatment of the pentamethyl glucose derivative with dilute acid hydrolyzes only the acetal methyl group. Haworth determined that the free hydroxyl group is on C5 of the hydrolyzed ether, showing that the cyclic form of glucose is a pyranose. 

Model compounds of bis-THF structure prepared for NMR correlation studies observation that H NMR shifts of acetate methyl groups correlate with relative configuration of C(15)/C(16) and C(23)/C(24) in uvaricin (later proven to be correct). 

The acetogens Chlostridium thermoaceticum and Chlostridium formiaceticum grow by sugar fermentation to produce acetate, but can also grow on CO2 and H2. In this metabolism, CO2 is converted to acetate. In the first step, CO2 reacts to the acetate methyl group and this reaction is catalyzed by the tungstoenzyme formate dehydrogenase (FDH),... 

Guarea thompsonii has been reported" to contain 6,12a-diacetoxymethyl angolensate (74). The 12a-acetate methyl group resonance appears at S 1.50 as a result of shielding by the furan ring. 

The differentiation of threo- and erythro-isomers of 1-substituted glycerol obtained by thermodynamically controlled isopropylidenation has been achieved by observation of values for the acetal methyl groups in H n.m.r. spectra for terminal isopropylidene is 0.05 p.p.m., since only one methyl group is shielded by the chairs, whereas for the at-threo isopropylidene group aS 4. 0.05 The values of aS were obtained for twenty-eight alditol isopropylidene derivatives. Observed coupling constants for protons in tetritol and... 

IH). Apparently a nonose structure as indicated above or some other combination, possibly glycosidic, of these components can be given for the various sialic-neuraminic acids and derivatives. These appear to differ in the number and type of acylating groups and in the presence of esters and acetal methyl groups. 

The structures of all Lycopodium alkaloids isolated thus far may be accommodated within the polyacetate biogenetic hypothesis proposed by Conroy 27) which has been alluded to in earlier sections of this review. His scheme proposes that the alkaloids are formed from two 3,5,7-triketooctanoic acid chains. The manner in which the two chains combine is illustrated by the numbering system proposed b " Wiesner (26) and adopted in this review. The odd-numbered C atoms represent the acetate carboxyl and the even-numbered C atoms the acetate methyl groups. This biogenetic scheme was put forward at a time when the structures of only a few alkaloids were known annotinine, lycopodine, a- and j8-obscurine, and selagine. It is perhaps more than coincidental that it also accommodates the novel structural types found in cernuine and serratinine. 

Nickell potassium acetate Methyl groups from 1,1,1-trihalides... 

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