Propargyl radical: ab initio anharmonic modes and the polarized infrared absorption spectra of matrix-isolated HCCCH2.

Abstract

The propargyl radical has twelve fundamental vibrational modes, gamma(vib)(HCCCH2) = 5a1 [symbol: see text] 3b1 [symbol: see text] 4b2, and nine have been detected in a cryogenic matrix. Ab initio coupled-cluster anharmonic force field calculations were used to help guide some of the assignments. The experimental HC=:C-:CH2 matrix frequencies (cm(-1)) and polarizations are a1 modes--3308.5 +/- 0.5, 3028.3 +/- 0.6, 1935.4 +/- 0.4, 1440.4 +/- 0.5, 1061.6 +/- 0.8; b1 modes--686.6 +/- 0.4, 483.6 +/- 0.5; b2 modes--1016.7 +/- 0.4, 620 +/- 2. We recommend a complete set of gas-phase vibrational frequencies for the propargyl radical, HC=:C-:CH2 2 X (2)B1. From an analysis of the vibrational spectra, the small electric dipole moment, mu(D)(HCCCH2) = 0.150 D, and the large resonance energy (HCCCH2), roughly 11 kcal mol(-1), we conclude that propargyl is a completely delocalized hydrocarbon radical and is best written as HC=:C-:CH2.

Cite this paper

@article{Jochnowitz2005PropargylRA, title={Propargyl radical: ab initio anharmonic modes and the polarized infrared absorption spectra of matrix-isolated HCCCH2.}, author={Evan B Jochnowitz and Xin Zhang and Mark R Nimlos and Mychel E. Varner and John F. Stanton and G Barney Ellison}, journal={The journal of physical chemistry. A}, year={2005}, volume={109 17}, pages={3812-21} }