Acryloyl chloride and acryloyl isocyanate (CH2=CHC(O)X, X = Cl, NCO): a HeI photoelectron spectroscopy and theoretical study.

Acryloyl isocyanate CH(2)=CHC(O)NCO is quantitatively prepared by the metathesis reaction between CH(2)=CHC(O)Cl and AgNCO. Also, jointly with acryloyl chloride, their molecular and electronic structures have been investigated by photoionization mass spectroscopy (PIMS), HeI photoelectron spectroscopy (PES), and theoretical calculations. CH(2)=CHC(O)NCO was theoretically predicted to prefer the trans-cis (tc) conformation as the most stable conformer, with the C=O bond trans to the C=C bond and cis to the NCO moiety. IR and Raman spectra also suggest the presence of the trans-cis (tc) conformation only. Calculations of the cationic-radical form were carried out in order to compare their properties with those of the neutral molecules. It is worthwhile mentioning that both compounds retain planar structures after ionization. After structural optimizations, a theoretical study involving the calculation of the ionization energies using orbital valence Green's functional (OVGF) was performed. The ionization energies of different bands in the photoelectron spectrum are in good agreement with the calculated values from the OVGF method. The first vertical ionization energies of CH(2)=CHC(O)Cl and CH(2)=CHC(O)NCO are determined to be 10.97 and 10.68 eV, respectively. The HOMOs correspond to the ionization of electrons mainly localized on the pi(C=C) or the pi(NCO) orbitals: {4a''(pi(C=C))}(-1) and {5a''(pi(NCO))}(-1), respectively.