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Vibrational spectra and conformational behavior of (cyanomethyl)cyclopropane
Author(s) -
Wurrey C. J.,
Yeh Y. Y.,
Weakley M. D.,
Kalasinsky V. F.
Publication year - 1984
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250150310
Subject(s) - conformational isomerism , cyclopropane , raman spectroscopy , chemistry , infrared , enthalpy , infrared spectroscopy , liquid phase , phase (matter) , spectral line , crystallography , computational chemistry , analytical chemistry (journal) , thermodynamics , molecule , organic chemistry , ring (chemistry) , physics , astronomy , optics
The infrared spectra (4000–400 cm −1 ) of gaseous, liquid and solid (cyanomethyl) cyclopropane have been recorded for the first time. Additionally, the Raman spectra (3500–50 cm −1 ) of condensed phases of this substance have also been obtained. ‘Extra’ Q branches have been observed in the gas‐phase infrared spectrum, and six liquid‐phase Raman doublets (two of which are also seen in the infrared spectrum of the liquid) have also been observed, wherein one member of each doublet vanishes once the polycrystalline solid state spectrum is obtained. These data have been interpreted in terms of a two conformer ( gauche/cis ) fluid‐phase equilibrium for (cyanomethyl)cyclopropane, with only the gauche conformer remaining in the solid phase. The temperature behavior of the 774/756 and 835/855 cm −1 liquid‐phase Raman doublets yields an enthalpy difference between conformers of 0.72±0.10 kcal mol −1 , with the gauche conformer the more stable. This Δ H value implies a room‐temperature conformational equilibrium for (cyanomethyl)cyclopropane composed of 87% gauche and 13% cis rotamers in the liquid phase. In addition, a vibrational assignment for the 33 normal modes of (cyanomethyl)cyclopropane has been proposed, and it is in excellent agreement with the previously published vibrational assignments for three (halomethyl)cyclopropanes.