Ying-Sing Li

FT-IR spectra of matrix isolated complexes between some alkanethiols and sulfur dioxide

Abstract Complexes formed between some alkanethiols and sulfur dioxide have been prepared by condensing the reagents diluted in argon and in nitrogen at 12-14K. The 1:1 RSH· · ·S0 2 complexes were identified from the infrared spectra of the mixtures of ethanethiol, iso-propanethiol, and tert-butanethiol, respectively, with sulfur dioxide in argon and in nitrogen matrices. Vibrational assignments and the possible interaction sites were suggested.

Spectra and structure of organogermanes. XXIV. Microwave spectra, quadrupole coupling constants, and structure of methylgermyl bromide

The microwave spectra from 26.5 to 39.0 GHz of eighteen isotopic species of methylgermyl bromide, 12CH3GeH2Br, 12CH3GeD2Br, and 13CH3GeH2Br for three of the naturally occurring isotopes of germane, 70Ge, 72Ge, and 74Ge, as well as the two of bromine, 79Br and 81Br, have been measured and assigned. From these data, substitution structural parameters were determined except for the methyl group. The determined parameters are: r(Ge–Br)=2.308±0.002 A, r(Ge–C)=1.933±0.002 A, r(Ge–H)=1.520±0.001 A, r(C–Hs)=1.100±0.012 A, r(C–Ha)=1.097±0.030 A, CGeBr=107.0±0.2°, HGeH=111.5±0.1°, HGeC=112.2±0.1°, GeCHs=110.3±4.7°, and GeCHa=111.9±1.7°. From a diagnostic least‐squares adjustment to fit 36 rotational constants, r0 structural parameters were also obtained. Quadrupolar coupling constants have been obtained. These results are compared to similar quantities in some related molecules.

Analysis of torsional spectra of molecules with two internal C3v rotors. XXIII. Microwave, infrared, and Raman spectra, barriers to internal rotation, and vibrational assignment of 3,3,3‐trifluoro‐2‐methylpropene

The microwave spectrum of 3,3,3‐trifluoro‐2‐methylpropene, H2C=C(CH3)CF3 has been recorded from 18.5 to 39.0 GHz. Only a‐type transitions were observed and R‐branch assignments have been made for the ground vibrational state as well as for three vibrational excited states of the CF3 torsion and one excited state of the CH3 torsion. The rotational constants for the ground vibrational state were found to have the following values: A=3549.25±0.35, B=2465.82±0.05, and C=1978.25±0.02 MHz. The dipole moment components were determined from the Stark effect to be ‖μa‖=2.44±0.01, ‖μb‖=0.59±0.09, and ‖μt‖=2.51±0.03 D. From an analysis of the internal rotational splittings, the threefold barrier for the methyl group was found to be 603±19 cm−1 (1.72 kcal/mol). This value is consistent with the value of 610±4 cm−1 (1.74 kcal/mol) obtained from the far infrared spectrum where the fundamental was assigned at 160.9 cm−1, but only if kinetic coupling between the perfluoromethyl and methyl torsion is taken into account. T...

Complex formation of sulfur dioxide with HSCH2CH2SH, CH3SCH2SH, and CH3SSCH3 in argon matrices

Abstract Complex formation of three organosulfur compounds, including 1,2-ethanedithiol, (methylthio)methanethiol, and dimethyl disulfide, with sulfur dioxide have been prepared by condensing the reagents diluted in argon at 12–14 K. The 1:1 complexes were identified from the infrared spectra of the mixtures of these sulfur compounds with sulfur dioxide in argon matrices. In each case, red shifts for the SO stretching vibrations and slight blue shifts for the OSO bending mode from the corresponding vibrations of the “free” SO 2 were observed. Perturbation of some vibrations of the organosulfur subunit were characterized in the complexes. The experimental results suggested the existence of two different 1:1 (methylthio)methanethiol/SO 2 complexes resulting from the SO 2 bonding to different sulfur atoms in the organosulfur compound.

Microwave spectrum and conformation of bicyclo[3,3,1]-nonan-9-one

Abstract The microwave spectrum of bicyclo[3,3,1] nonan-9-one has been recorded from 18.0 to 26.5 GHz. A -type R-branch transitions in the ground state and the excited state have been assigned. The ground-state rotational constants were determined to be A = 1507.54±0.06, B = 1495.09±0.07, and C = 1372.13±0.01 MHz. These data indicate that the molecule exists predominantly in the chair-chair form.

Conformation and barrier to internal rotation of 3-methyl-2-cyclopenten-1-one by microwave spectroscopy

Abstract The microwave spectrum of 3-methyl-2-cyclopenten-1-one has been recorded from 18.0 to 26.5 GHz. Both a -type and c -type R -branch transitions in the ground state and the three vibrationally excited states of the ring-bending mode have been assigned. The ground state rotational constants are determined to be A = 5799.78 ± 0.23, B = 2028.79 ± 0.02, and C = 1546.77 ± 0.01 MHz. These data are consistent with a planar heavy-atom skeleton. From an analysis of the internal rotational splittings in the first methyl torsional state, the threefold barrier for the methyl group has been determined to be 1.71 ± 0.09 kcal mol −1 .

Conformational identification of cyclohexylphosphine by microwave spectroscopy

Abstract The microwave spectra of cyclohexylphosphine have been recorded in the 18.0–26.5 GHz region. A -type rotational transitions have been assigned. The ground state rotational constants were determined to be A = 4153.75 ± 0.23, B = 1362.31 ± 0.01 and C = 1104.14 ± 0.01 MHz for C 6 H 11 PH 2 , and A = 4030.03 ± 0.25, B = 1312.72 ± 0.01 and C = 1072.33 ± 0.01 MHz for C 6 H 11 PD 2 . From the experimental rotational constants, it is suggested that the assigned spectra have resulted from the chair conformation with the gauche phosphine group in an equatorial position (CESG). This form is believed to be the most populated conformational isomer in the gas phase.

Far infrared spectrum of methyl chloride

Abstract The pure rotational spectrum of methyl chloride recorded in the range 6–60 cm−1 with a resolution of 0.06 cm−1 using a Fourier transform far-IR spectrometer is presented. Rotational assignments have been made for both the CH2 35Cl and the CH3 37Cl species in the ground vibrational state and the υ3 = 1 excited vibrational state. No K components for a given J transition have been resolved. The rotational constants B and the distortion constants, DJ, have been derived from the analyses of these data and the values obtained are in agreement with those previously derived from microwave spectroscopic data.

Conformational identification and dipole moment of 4-fluoro-1-butene by microwave spectroscopy

Abstract The microwave spectrum of 4-fluoro-1-butene has been recorded in the frequency region 26.5–40.0 GHz. A -type rotational transitions in the ground vibrational state have been assigned. The effective rotational constants and centrifugal distortion constants were determined to be A = 19 196 ± 323, B = 2132.48 ± 0.01, C = 2112.52 ± 0.01 MHz, D J = 0.70 ± 0.03 and D JK = −26.16 ± 0.05 kHz. Analysis of the measured Stark effects gave a dipole moment of 1.80 D with components of | u a | = 1.62 ± 0.01, | u b | = 0.68 ± 0.05 and | u c | = 0.39 ± 0.14 D. From the experimental rotational constants and dipole moments, it is suggested that the assigned spectra have resulted from the skew—trans conformer.