Linear methyl-phenyl-carbonate

The reaction of a series of anilines with methyl 2,4,6-trinitrophenyl carbonate in water proceeded via a concerted mechanism as revealed by a linear Br0nsted-type plot with slope of 0.7. A Yukawa-Tsuno plot was linear for the alkaline hydrolysis of a series of Y-phenyl phenyl carbonates with p = 1.21 and r = 0.33, consistent with a concerted mechanism. 

The acid cleavage of the aryl— silicon bond (desilylation), which provides a measure of the reactivity of the aromatic carbon of the bond, has been applied to 2- and 3-thienyl trimethylsilane, It was found that the 2-isomer reacted only 43.5 times faster than the 3-isomer and 5000 times faster than the phenyl compound at 50,2°C in acetic acid containing aqueous sulfuric acid. The results so far are consistent with the relative reactivities of thiophene upon detritia-tion if a linear free-energy relationship between the substituent effect in detritiation and desilylation is assumed, as the p-methyl group activates about 240 (200-300) times in detritiation with aqueous sulfuric acid and about 18 times in desilylation. A direct experimental comparison of the difference between benzene and thiophene in detritiation has not been carried out, but it may be mentioned that even in 80.7% sulfuric acid, benzene is detritiated about 600 times slower than 2-tritiothiophene. The aforementioned consideration makes it probable that under similar conditions the ratio of the rates of detritiation of thiophene and benzene is larger than in the desilylation. A still larger difference in reactivity between the 2-position of thiophene and benzene has been found for acetoxymercuration which... 

The chain scission also can start truly randomly and not only at the weaker bond. For polymers containing linear backbones, in addition to p-scissions, it is possible to have a-scissions, methyl scissions or even hydrogen scissions. The scission of a C-H bond is thermodynamically unfavorable at low temperatures and is not too common at temperatures where the other scission can take place. The a-scission is more frequent. It refers to the breaking of a o bond to an sp2 carbon. For polystyrene for example, the a-scission leads to the formation of a phenyl radical and a polymeric radical (and it is not a chain scission). 

Two taxane alkaloids have been investigated by diffraction techniques taxine A (la) [23] and 2 deacetoxyaustrospicatine (41) [49], The results gave important information on the orientation of the side chain relatively to the terpenoid core. In both cases the aromatic ring is close to the terpenoid core, but in 4f the phenyl and the catbonyl are antiperiplanar, whereas in taxine A they are synclinal (cf. C and A in Scheme 3). As a result, the protons closer to the phenyl ring are H(6a) in taxine A and H(14a) in 4f. This is in accordance with the results of the H-NMR analysis [46], In 4f, the conformation with C-l and the phenyl antiperiplanar is stabilized by hydrophobic interactions with the methyl of the 13-acetate [49], The X-ray features of the terpenoid core of 4f and taxine A show linear strain at several carbon-carbon bonds, as generally observed in taxoids [55]. 

Atoms such as O, N, S, and Si can take the place of the carbon atom within the backbone of the chain. For example, the linear chain for the silicones is shown below where R represents a chemical radical or a pendent group. The R radical in the repeating unit may be a methyl or phenyl group. 

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