Ratnakar K. Gosavi

Ultraviolet absorption spectra of CdCH3, ZnCH3, and TeCH3

Ultraviolet absorption spectra were recorded for the transient radicals CdCH3, ZnCH3, and TeCH3 produced in the flash photolysis of the appropriate dimethyl metals. For CdCH3 and ZnCH3 two systems were observed and assigned to the two transitions A 2E← x2 A1 and B 2E← x2 A1. For the TeCH3 radical only one system was observed which was assigned to the B← x transition. The progressions in the spectra are assigned to the upper state carbon‐metal stretching vibration (ν′3) and CH3 symmetric deformation vibrations (ν′2).

The UV absorption spectrum and geometry of the HS2 radical

Abstract The ultraviolet absorption spectrum of the transient HS 2 radical produced in the flash photolysis of H 2 S 2 was recorded. The spectrum observed in the λ = 3070–3800 A region is assigned to the A 2 A′ ← X 2 A″ electronic transition, and three progressions to the SS stretching (ν′ 1 ), SSz.sbnd;H bending (ν′ 2 ) and SH stretching (ν′ 3 ) vibrations of the 2 A′ upper electronic state. Open-shell CNDO/2 calculations were carried out to optimize the ground state ( 2 A″) molecular geometry. For comparison, similar calculations were also performed on the HO 2 radical. HS 2 is bent in the ground state and nearly linear in the ( 2 A′) and ( 4 A″) excited states.

AB initio molecular orbital studies of the structural and spectral properties of dichlorosilylene, SiCl2

Abstract Molecular geometry optimization of X 1 A 1 ground and several singlet and triplet excited states of SiCl 2 have been carried out at the RHF SCF level with 6-31G * basis set. For the ground 1 A 1 state, the computed bond length ( R (Si-Cl) = 2.096 A), bond angle (∠ClSiCl = 101.19°) and harmonic vibrational frequencies (ν 1 = 530.9, ν 2 = 212.8 and ν 3 = 521.1 cm −1 ) are all in good agreement with the experimental values reported. The calculated electronic excitation energy of 30677 cm −1 for the A 1 B 1 -X 1 A 1 transition also compares well with the experimental value of ≈ 30000 cm −1 .

Ab initio molecular orbital calculations on thirene: The thermodynamic stability of five C2H2S isomers

Abstract A non-empirical SCF molecular orbital study using an STO-4G minimal basis set has been carried out on the thiirene molecule and on four of its C2H2S isomeric structures. The geometries of all five structures have been optimized in both their lowest singlet and triplet states. The computed thermodynamic stabilities of the various structures agree with experimental observations and, in general, with the predicted trends in the C2H2O analogs.

Abinitio molecular orbital calculations on the reaction path of the ketocarbene–ketene rearrangement

An ab initio type SCF MO study using a double zeta quality basis set has been carried out on the formylmethylene–ketene rearrangement reaction which is the last step of the Wolff rearrangement–decomposition sequence of α‐diazoketones and α‐diazoesters. The ketene structure is computed to be 74.3 kcal/mole more stable than the isomeric formylmethylene and the reaction features a computed activation energy of 5.7 kcal/mole, corresponding to a bridged activated complex. The computed geometry of the ketene molecule is in good agreement with the experimental geometry.

A theoretical study on the thermodynamic properties of the formation and decomposition of methyloxirane via triplet mechanisms

Abstract Molecular unrestricted Hartree-Fock calculations with geometry optimization have been carried out on eight triplet isomers of C 3 H 6 O considered to be possible intermediates in the addition of O( 3 P) atoms to propylene and in the Hg( 3 P) sensitization of methyloxirane. The computed thermodynamic stabilities reveal that four triplet states are available in the former and eight triplet states are available in the latter reaction. The isomer CH 3 ĊHCH 2 Ȯ is more stable than ȮCHCH 3 ĊH 2 . This latter feature gives a satisfactory explanation for the experimental observation that in the O( 3 P) + C 3 H 6 reaction propionaldehyde is the major carbonyl product.

A preliminary investigation on the thermodynamic stability of triplet carbenoid isomers of silaethylene

Abstract Ab initio SCF MO calculations on the lowest triplet states of carbenoid isomers of silaethylene were carried out with an STO-4G basis set using Pople and Nesbets unrestricted Hartree—Fock method. All geometrical parameters were optimized. The results predict that both methylsilylene (H 3 CSiH) and silylcarbene (HCSiH 3 ) are thermodynamically more stable than silaethylene (H 2 CSiH 2 ) in their lowest triplet state. Silylcarbene has the lowest triplet state energy.

A comparative molecular orbital study on the low lying singlet and triplet states of ethylene oxide

Two cross sections of the energy hypersurface for the ethylene oxide molecule, one involving a ring distortion, the other rotation about the C-C bond, have been studied by the semi-empirical and non-empirical SCF molecular orbital methods. The results indicate a ring distorted equilibrium geometry for the excited states of the molecule and implicate the lowest triplet state as an intermediate in the C2H4+ O(3P)→ ethylene oxide reaction.The results of the various types of calculations are compared.

Ab initio molecular orbital studies of fluorine dioxide, chlorine dioxide and their isomeric peroxy radical forms

Abstract Molecular geometry optimization of the 2 B 1 , 2 B 2 , 2 A 1 and 2 A 2 states of OFO and the 2 A ″ and 2 A ′ states of FOO has been carried out at the RHF-SCF level with 6–31G and 6–31G* basis sets. Total energies were computed by CI calculations at the SCF level optimized geometry. Similar calculations were also performed on OClO and ClOO with 6–31G, 6–31G+ d functions on Cl and 6–31G* basis sets. The results are in general agreement with the experimental observations reported in the literature. The ground state is computed to be the 2 A ″ state for both the FOO and ClOO radicals, 2 B 2 for OFO and 2 B 1 for OClO. Net atomic charges and dipole moments were calculated by the Mulliken population analysis.

Lowest triplet state reaction surface studies for the isomerization methylsilylene → silaethylene → silylcarbene

Abstract Ab initio SCF MO calculations on the lowest triplet reaction path for the isomerization methylsilylene → silaethylene → silylcarbene were carried out with an STO-4G basis set using Pople and Nesbets unrestricted Hartree-Fock method. Molecular geometries of the intermediates along the reaction path were fully optimized. Computed potential energy surfaces show that isomerization of methylsilylene to silaethylene requires an activation energy of 83.8 kcal/mole, and that of silaethylene to silylcarbene, 92.5 kcal/mole.