Microwave, structural, conformational, vibrational studies and ab initio calculations of isocyanocyclopentane.
The infrared and Raman spectra (3200-50 cm(-1)) of the gas, liquid or solution, and solid have been recorded of isocyanocyclopentane, c-C5H9NC. FT-microwave studies have also been carried out and 23 transitions were recorded for the envelope-axial (Ax) conformer. Variable temperature (-65 to -100 °C) studies of the infrared spectra (3200-400 cm(-1)) dissolved in liquid xenon have been carried out. From these data, both the Ax and envelope-equatorial (Eq) conformers have been identified and their relative stabilities obtained. The enthalpy difference has been determined to be 102±10 cm(-1) (1.21±0.11 kJ mol(-1)) with the Ax conformer the more stable form. The percentage of the Eq conformer is estimated to be 38±1% at ambient temperature. The conformational stabilities have been predicted from ab initio calculations by utilizing several different basis sets up to aug-cc-pVTZ from both MP2(full) and density functional theory calculations by the B3LYP method. Vibrational assignments have been made for the observed bands for both conformers with initial predictions by MP2(full)/6-31G(d) ab initio calculations to obtain harmonic force constants, wavenumbers, infrared intensities, Raman activities and depolarization ratios for both conformers. The structural parameter values for the Ax form are; for the heavy atom distances (Å): C≡N = 1.176 (3); Cα-N=1.432 (3); Cα-Cβ,Cβ'=1.534 (3); Cβ-Cγ,Cγ'=1.542 (3); Cγ-Cγ'=1.554 (3) and angles (°):∠Cα-N≡C=177.8 (5); ∠CβCα-N=110.4 (5); <CβCαCβ' = 102.9 (5); ∠CαCβCγ=103.6 (5); <CβCγCγ' = 105.9 (5). The results are discussed and compared to the corresponding properties of some related molecules.
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA. Electronic address: durigj@umkc.edu.
James R
JR
Durig
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Joshua J
JJ
Klaassen
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Dattatray K
DK
Sawant
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Bhushan S
BS
Deodhar
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Savitha S
SS
Panikar
Department of Chemistry, Kent State University, Kent, OH 44242, USA.
Ranil M
RM
Gurusinghe
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
Ikhlas D
ID
Darkhalil
Department of Chemistry, Kent State University, Kent, OH 44242, USA.
Michael J
MJ
Tubergen
D003517:Cyclopentanes / Q000737:chemistry*; D017953:Isocyanates / Q000737:chemistry*; D008872:Microwaves; D008956:Models, Chemical; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared / Q000379:methods; D013059:Spectrum Analysis, Raman; D014732:Vibration; D014978:Xenon / Q000737:chemistry
D003517:Cyclopentanes; D017953:Isocyanates; D014978:Xenon
Conformational stability; Five membered rings; Isocyanide; Molecular Structure; Vibrational assignment; Xenon solutions