Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. XII. 1,2-Di-tert-butyl-3,3-dimethylcyclopropene.

The synthesis of 1,2-di-tert-butyl-3,3-dimethylcyclopropene (I) is performed and its IR and Raman spectra are measured. Optimized geometries of I are obtained at the HF/6-31G* and CCSD/cc-pVDZ levels. The ab initio calculated spectra are used for the assignments of the experimental spectral data.

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. XI. Secondary periodicity.

Regularities of changes in the structural parameters and vibrational wavenumbers for certain moieties of the title compounds are presented. The optimized geometrical parameters and the force fields of the di- and monosubstituted 3,3-dimethylcyclopropenes were determined at the HF/3-21G* and HF/DDAll pseudopotential levels, respectively. These theoretical levels were chosen because of peculiarities of Gaussian 03 suite of programs for the Sn and Pb atoms.

s-trans-1,3-butadiene and isotopomers: vibrational spectra, scaled quantum-chemical force fields, fermi resonances, and C-H bond properties.

Quadratic quantum-chemical force fields have been determined for s-trans-1,3-butadiene using B3LYP and MP2 methods. Basis sets included 6-311++G, cc-pVTZ, and aug-cc-pVTZ. Scaling of the force fields was based on frequency data for up to 11 isotopomers, some of these data being original.