Cyclopropanones theoretical studies

The rearrangements of 3-methylbut-l-ene oxides" and l,2-epoxybut-3-ene on lithium phosphate have been studied, and a detailed theoretical study of the rearrangement of allene oxide (342) to cyclopropanone (344), which shows that the transformation proceeds via an intermediate oxyallyl (343), has been presented. It has been shown that aldehydes, ketones, and cyclic ethers are all produced... 

The theoretical studies suggest allene oxide is about 23 kcal mol-1 (96 kJ mol-1) less stable than cyclopropanone, while methylene thiirane is 7 kcal mol-1 (29 kJ mol-1) more stable than cyclopropanethione < 91 PS(58)i 79). 

The isomerization reaction of alkylidene oxiranes, i.e. allene epoxides, to cyclopropanones has stimulated many investigations. Several experimental and theoretical studies suggest that the reaction proceeds through an oxyallyl intermediate. 

Of the theoretical studies that have appeared, the MINDO/3 semiempirical MO treatment, developed by Dewar, has been expanded to unrestricted open-shell treatment by Bischof and applied to a series of radicals including the cyclopropyl species. A MINDO/3 study of the thermal decarbonylation of cyclopropanone by Shevlin and co-workers predicts the non-linear cheletropic mode of the reaction (A/f 41 kcalmol" ) to be favoured by ca. 45kcalmol over the linear mode, in... 

The only gaseous products identified are ethene and carbon monoxide, formed in equal amounts (Thomas and Rodriguez, 1971 Rodriguez et al., 1976). Several theoretical studies of the mechanism of process (I) have been reported (Martino et al., 1977 Yamabe et al., 1979 Sevin et al., 1981). Oxyallyl, shown as the primary product in (n), has been suggested as a possible intermediate to polymer formation that appears on the walls of reaction vessels in laboratory studies of cyclopropanone photolysis. This molecule is expected to have a small energy barrier to its recyclization (Olsen et al., 1971 Liberies et al., 1973). If it is formed in (H), its possible fate in the atmosphere is open to conjecture. 

The ultraviolet absorption spectrum of cyclohexanone reflects the n jt transition common to all carbonyls see figure IX-E-1. The data derived from gas-phase measurements of the cross sections for cyclohexanone from two different research groups [National Center for Atmospheric Research (NCAR) and Ford Scientific Laboratories (Ford)] are in reasonable agreement (Iwasaki et al., 2008). The cyclohexanone cross sections as measured in cyclohexane solution by Benson and Kistiakowski (1942) had indicated seemingly low values (cross sections shown here is significantly less than those observed for cyclopropanone, cyclobutanone, and cyclopentanone, and in fact, all other carbonyls considered in this work. It is not obvious why these significant differences exist in the probability for the n -> 7T transition for cyclohexanone and that of the other cyclic ketones and most other carbonyl compounds. Theoretical studies will be important in defining the reasons for these differences. 

When seemingly simple organic structures defy isolation, this usually stimulates many theoretical and experimental studies in an effort to rationalize anomalous behavior. In the case of cyclopropanone, the possibility was considered that the molecule might preferably exist as an open-chain dipolar structure rather than as the cyclic ketone ... 

Cyclopropanon.es are highly reactive organic systems containing a number of labile sites on a small carbon skeleton. They represent valuable substrates for studying theoretical aspects of the chemistry of small strained ring systems and are of special interest in synthesis because of the variety of transformations in which they take part. 

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