Vinylidene: the final chapter?

• Published in: Journal of the American Chemical Society Vol. 112; no. 24; pp. 8714 - 8719
• Main Authors: Gallo, Mary M, Hamilton, Tracy P, Schaefer, Henry F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.1990
• Subjects: 400201 - Chemical & Physicochemical Properties; ACETYLENE; ALKYNES; CALCULATION METHODS; CHEMICAL REACTIONS; Chemistry; DATA; ELECTRONIC STRUCTURE; ENERGY LEVELS; Exact sciences and technology; GROUND STATES; HYDROCARBONS; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ISOMERIZATION; Kinetics and mechanisms; NUMERICAL DATA; Organic chemistry; ORGANIC COMPOUNDS; RADICALS; Reactivity and mechanisms; THEORETICAL DATA; VINYLIDENE RADICALS; Vibrational transition; Carbene; SCF method; Hydrocarbon; Ab initio method; Isomerization; Transition state; Theoretical study; Ground state; SD CI method; Conformation
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00180a011

Ab initio molecular electronic structure theory is used to study the electronic ground state vinylidene-acetylene isomerization. Vinylidene, acetylene, and the transition state connecting them are located at various levels of theory, including correlated levels, and with large basis sets. The highest level and basis set with which geometry optimizations are performed is the CCSD level with the TZ+2P basis set. These structures are characterized by harmonic vibrational analyses as minima or transition states. Single-point energies also are computed at higher levels of theory, the highest being CCSD/QZ+3P, for all three structures. The effects of carbon atom f functions and hydrogen atom d functions are also explicitly considered. A classical barrier to isomerization from vinylidene to acetylene of {approximately}3 kcal/mol is found. The {Delta}E for isomerization is predicted to be {approximately}43 kcal/mol.