Trans-1,2-dideuteriocyclobutane

M. A. Lowe, P. J. Stephens, and G. A. Segal, Cfeew. Phys. Lett., 123,108 (1986). The Theory of Vibrational Circular Dichroism trans-1,2-Dideuteriocyclobutane and Propylene Oxide. 

A. Annamalai, T. A. Keiderling, and J. S. Chickos, /. Am. Chem. Soc., 106, 6254 (1984). Vibrational Circular Dichroism of (rons-1,2-Dideuteriocyclobutane. A Comparison trf Fixed Partial Charge and Localized Molecular Orbital Theories with Different Force Fields. A. Annamalai, T. A. Keiderling, and J. S. Chickos, /. Am. Chem. Soc., 107, 2285 (1985). Vibrational Circular Dichroism of trans-1,2-Dideuteriocyclobutane. Experimental and Cal-culational Results in the Mid-Infrared. 

Comparison of the experimental spectra of trans-1,2-dideuteriocyclobutane [15] with the FPC as well as with the LMO model shows the former to be considerably more reliable. 

The preferred sp3 hybridization for saturated fluorocarbons is a major driving force for the easy polymerization of TFE to PTEF with more exothermic enthalpy change (Scheme 1.34) [2]. The it-bond energy of tetrafluoroethylene is 52 kcal/mol, which is smaller than that of ethylene, 64-65 kcal/mol [3].The easy [2 + 2] cycloadditions of gem-difluoroalkenes (thermal concerted reactions of which are forbidden) proceed stepwise via biradical intermediates. The intermediacy of a biradical is supported by the fact that a 1 1 mixture of the cis- and trans-dideuteriocyclobutanes (7 and 8) was obtained in the [2 + 2] cycloaddition of TFE with cis- (4) and frans-dideuterioethylene (5) [4] (Scheme 1.34). 

Polavatapu, et al. (128) have identified a VCD band near 12(X) cm in phenylcaibinols that correlates with configuration. Wieser and co-workers (129, 130) have recently reported FTIR-VCD spectra of chiral methyloxetan molecules. In the area of theoretical calculations, Lx>we, Stephens, and Segal (131, 132) have implemented the theory of Stephens (118) in calculations on trans-1,2,-dideuteriocyclopropane, tron5-l,2-dideuteriocyclobutane, and propylene oxide. For the latter two molecules, favorable agreement with experiment was found. The first application of VCD to kinetic analysis has also been reported for (1/ , 2R)-dideuteriocyclobutane thermolysis (133). 

Subsequently, Chickos examined the pyrolysis of cis-anti- and trans-1,2-dimethyl-cw-3,4-dideuteriocyclobutane at 510°C in a flow system. The cis-anti-cis isomer undergoes fragmentation to cis- and ra/z -propene-Ji in a 1.5 1 ratio, while the ratio of the trans- to cw-propenes from the trans-cis isomer is 1 1 at conversions of 26 and 56 %, respectively (Scheme 5.24). The Principle of Conservation of Orbital Symmetry predicts that the retro 2 + 2 reaction should proceed in a + a fashion if it were a concerted process. If this were the case, then the propylene formed from the cis-anti-cis isomer should have been exactly a 1 1 mixture of deuterium isomers. The fact that it is not a 1 1 mixture rules out concert as the sole reaction pathway initiated by cleavage of the more substituted bond. 

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