Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The Raman spectrum of gaseous nitrocyclopropane, c—C3H5NO2 has been recorded from 3500 to 30 cm-1. The interesting internal NO2 torsion was observed at 85±2cm-1 from which a barrier to internal rotation in the vapor state of 1680±70 cm-1 (4.8±0.2 kcal mol-1) was calculated. It is shown that this torsional frequency is consistent with the relative intensities of the vibrational excited states in the microwave spectrum. This barrier value is compared to those for several other NO2 substituted hydrocarbons as well as for the corresponding isoelectronic BF2 substituted molecules. The high barrier value supports the structural arguments that there is significant pseudo-conjugation between the cyclopropane ring orbitals and the substituent NO2 group. A revised vibrational assignment is presented which is compared to the one previously given for the isoelectronic molecule, c-C3H5BF2, as well as for c-C3H5BCI2.
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