Spectra and structure of organophosphorus compounds. XV. Microwave spectrum of ethylphosphine

Abstract

The microwave spectra of CH3CH2PH2, CH3CH2PHD, and CH3CH2PD2 have been recorded in the range 18.0 to 40.0 GHz. A-type transitions were observed and assigned for both gauche and trans conformers of ethylphosphine, and b-type transitions observed and assigned for the gauche conformer. The dipole moment components for the gauche conformer were determined from the Stark effect to be: ‖μa‖= 0.86±0.01, ‖μb‖=0.73±0.07, ‖μc‖=0.45±0.05, and ‖μt‖=1.22±0.07 D. For the trans conformers, there was only one component of the dipole moment and it had a value of ‖μa‖= ‖μt‖=1.226±0.005 D. The relative intensity of nine pairs of lines for the gauche and trans were measured at room temperature, and from the ratio of intensities it was found that ethylphosphine exists as a 45% gauche and 55% trans mixture with an energy difference of 200±100 cm−1 and the trans the more stable conformer. With reasonable assumptions for the ethyl moiety, the following structural parameters were calculated: &CCP=110.1±0.2°, rPC=1.880±0.0002 Å and PH2 dihedral angle = 61±2° and for the gauche conformer &CCP= 115.2±0.2°, rPC=1.876±0.002 Å and PH2 dihedral angle = 180±2°.

The rotational spectrum of the CCP (XΠr2) radical and its C13 isotopologues at microwave, millimeter, and submillimeter wavelengths

“…17,19 Also listed in Table V are the C u P and/or C u C bond lengths present in other simple molecules. [28][29][30][31][32][33][34][35][36][37][38][39][40] The nature of the bonds between these atoms, i.e., single, double, or triple bonds, is illustrated in the first column. From the table, the range in bond lengths for a carbon-phosphorus single bond is 1.86-1.88 Å, 1.65-1.68 Å for a double bond, and a C w P triple bond is 1.54-1.59 Å.…”

Vibrational spectra and conformational behavior of cyclohexylphosphine

“…22 The results are shown in Table 1 together with the rotational constants of the EG conformer determined from L i ' s microwave experimental data." The agreement between the observed and calculated rotational constants suggests that the assumed structure is reasonable.…”

Spectra and structure of organophosphorus compounds. 16. Infrared and Raman spectra, vibrational assignment, and conformational analysis for isopropylphosphine and isopropylphosphine-d2

“…We hoped to be able to compare the potential function governing internal rotation around the C-P bond of isopropylphosphine with that determined for the similar bond in ethylphosphine. 3 The results of this study are reported herein.…”

“…The barriers to internal rotation of the methyl groups are in good agreement with those found by Durig et alu in a series of isopropyl compounds and show the expected upward trend when compared to the methyl torsional barriers found in ethylphosphine. 3 Clearly the problem of significant interest in this study is the determination of the more stable molecular conformation.…”