Overtone spectroscopy of propyne and propyne-d1

Abstract

Eigenstate resolved infrared/infrared double resonance spectroscopy of the 3ν1 overtone band of 1propyne: Intramolecular vibrational energy redistribution into a Corioliscoupled bath SubDoppler, infrared laser spectroscopy of the propyne 2ν1 band: Evidence of zaxis Coriolis dominated intramolecular state mixing in the acetylenic CH stretch overtone Spectroscopy and nonradiative relaxtion of propynal J. Chem. Phys. 77, 697 (1982); 10.1063/1.443884Electronimpact spectroscopy of the alkynes: A comparison of propyne and 1butyne with acetyleneThe vibrational overtone spectra of the acetylenic and methyl C-H stretches ofpropyne were obtained for the v = 1 to v = 6 and v = 1 to v = 7 levels, respectively. Propyne-dl was also studied and the methyl C-H stretching overtones were measured from v = 1 to the v = 7 level.The C-D stretch was observed only in the fundamental and first overtone regions. Lower level overtones were obtained by standard infrared techniques, while higher absorptions ( > 12000 cm -I) were obtained by intracavity dye laser photoacoustic spectroscopy. The C-H stretches in both molecules were analyzed in terms of the local-mode model, and harmonic frequencies (lU j ) and anharmonicities (Xu) were calculated. In propyne these values were (acetylenic C-H stretch) lUI = 3384 ± 5 cm -I and X l1 = -50 ± 1 cm -I and (methyl C-H stretch) lU m = 3037 ± 5 cm -I and Xmm = -65 ± 2 cm -I. In propyne-d I the methyl C-H stretch parameters were lU m = 3034 ± 5 cm -,I and X mm = -64 ± 2 cm -I. For propyne, a hot band (V9 -+ V9 + VV I ) accompanying the acetylenic C-H stretch was observed for v = 1-6 and the anharmonic interaction constant (X 19 = -23 ± 7 cm-I ) was calculated. A crossover from normal-to local-mode behavior has been observed for the methyl C-H stretches in propyne and propyne-d I at the v = 3 and 4 levels. Below v = 3 the symmetric and antisymmetric methyl C-H stretches are designated by the usual normal-mode notation (V2 and V6 in propyne; VI and V6 in propyne-dl), while for v>3 the single observed band is designated as a "methyl" C-H stretch, VV m • Peak absorption cross sections have been measured for aV I = 1-5, aV m = 3-5, aV 2 = 1 and 2, and the parallel component of2v6 in propyne, and for aV2 = 1 and 2, aV I = 1 and 2, aV m = 3 and 4, and the parallel component of2v 6 in propyne-dl. During the course of this work the spectral constants of 3,3,3-trifluoropropyne were redetermined. The harmonic frequency lUI is 3376 ± 6 cm -\ the anharmonicity X l1 is -49 ± 1 cm -I, and the anharmonic interaction constant X 17 is -17 ± 6 cm -I.

High-Resolution Absorption Spectroscopy of the 3ν1 and 3ν1 + ν3 Bands of Propyne

“…From the above values, we predict the vibrational term value of the 2 1 ϩ 3 level at 8691.03 cm Ϫ1 , 12 cm Ϫ1 lower than the value given by Baylor et al (18). We could easily identify this band in the FTIR spectrum, as presented in Fig.…”

“…The erroneous value given in Ref. (18) corresponds in fact to the maximum of the R-branch absorption. Similarly, we assigned the 1 ϩ 3 combination band, predicted at 5464.4 cm Ϫ1 to a Q-branch head observed at 5465.0 cm Ϫ1 in a highly congested region of the FTIR spectrum.…”

“…In particular, Baylor et al (18) did not mention this band in their previous FTIR investigation of propyne. They, however, assigned two bands to the 2 1 ϩ 3 and 5 1 ϩ 3 combination bands.…”

Ab initio anharmonic force field and equilibrium structure of propene

“…HC"CF is the molecule most affected by anharmonic resonances, but their combined effect is only 6 cm À1 on the m is (CH) frequency which may be considered as small. The overtone spectrum of propyne has also been measured up to v = 7 [56] and again, for ethynyl hydrogen, the frequency derived from Eq. (3), 3329 cm À1 is very close to the isolated frequency obtained from CD 3 C"CH, 3334 cm À1 [47].…”

Spectroscopy of the Acetylenic CH Stretch of Propyne-d3 in the Region of the Second Overtone

“…They reassigned the 4ν 1 band and showed that it is perturbed by 3ν 1 + ν 3 + ν 5 , where ν 3 and ν 5 are the C≡C and C-C stretching modes, respectively. Baylor et al (9) and Hofmann et al (10) investigated the vibrational overtone spectra of the nν 1 bands (n = 1-6) and of the nν m bands ( n = 1-7) of propyne. In addition, they studied the nν m bands (n = 1-7) and the fundamental and first overtone regions of the acetylenic C-D stretch of propyne-d 1 .…”