An experimental Raman and theoretical DFT study on the self-association of acrylonitrile.
The liquid structure of acrylonitrile (propenenitrile) has been investigated using Raman spectroscopy and density functional theory (DFT) ab initio calculations with the 6-311++G** basis set. Two different and complementary experimental approaches were undertaken: FT-Raman spectra of 13 acrylonitrile solutions in carbon tetrachloride (concentration range=0.25-12.0 mol.L-1) were studied in detail including principal component analysis (PCA) of the CN stretching band. Furthermore, dispersive Raman spectra of neat acrylonitrile were obtained at eight different temperatures from 238 up to 343 K. The complex and asymmetric acrylonitrile Raman CN stretching band can be decomposed into two components attributed to monomeric and self-associated forms. Ab initio results fully support this assignment and suggest that the self-associated complex is a nonplanar trimer held together by dipole-dipole interactions. At ambient temperature, the composition of acrylonitrile can be expressed as a mixture of 25% monomers and 75% trimers. Close to the boiling point, trimers still represent 65% of the liquid composition. The corresponding enthalpy of association was estimated to be -22+/-2 kJ.mol-1.
Alía
Jose M
JM
Department of Chemistry, University of California, Davis, California 95616, USA. josemaria.alia@uclm.es
Edwards
Howell G M
HG
Fawcett
W Ronald
WR
Smagala
Thomas G
TG
D000181:Acrylonitrile / Q000737:chemistry*; D008956:Models, Chemical; D025341:Principal Component Analysis; D011789:Quantum Theory; D012015:Reference Standards; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000379:methods* / Q000592:standards; D013696:Temperature
D000181:Acrylonitrile