Spectra and structure of organophosphorus compounds. XIV. Infrared and Raman spectra, vibrational assignment and the asymmetric potential function for ethylphosphine and ethylphosphine-d$sub 2$

Journal Article · Mon Sep 15 04:00:00 EDT 1975 · J. Chem. Phys., v. 63, no. 6, pp. 2303-2310

OSTI ID:4156102

Durig, J R; Cox, Jr, A W

The infrared spectra of gaseous and solid CH$sub 3$CH$sub 2$PH$sub 2$ and CH$sub 3$CH$sub 2$PD$sub 2$ have been recorded from 200 to 3500 cm$sup -1$. The Raman spectra of gaseous, liquid, and solid CH$sub 3$CH$sub 2$PH$sub 2$ and CH$sub 3$CH$sub 2$PD$sub 2$ have been recorded from 100 to 3500 cm$sup -1$. The gauche and trans isomers have been observed in the fluid phases and only the trans exists in the solid state. A vibrational assignment of the 24 normal modes has been made. Fundamental and hot band transitions have been observed for both the methyl and phosphino torsions. The methyl barrier in the trans d$sub 0$ molecule was determined to be 3.74plus-or-minus0.05 kcal/mole and 3.14plus-or- minus0.05 for the gauche d$sub 0$ molecule. The potential function for internal rotation around the C--P bond in CH$sub 3$CH$sub 2$PD$sub 2$ was determined and the following potential constants found: V$sub 2$=207plus-or-minus6 cm$sup -1$, V$sub 3$=785plus-or-minus5 cm$sup -1$, and V$sub 6$=-25plus-or-minus3 cm$sup -1$. The energy difference between the potential energy minima of the gauche and trans conformations is 150 cm$sup -1$, the trans being the more stable form. The calculated gauche--gauche barrier is 635 cm$sup -1$ (1.82 kcal/mole) and the trans--gauche barrier is 944 cm$sup -1$ (2.70 kcal/mole). A similar potential function was determined for the CH$sub 3$CH$sub 2$PH$sub 2$ isomer but the fit to this one-dimensional model was not as good as that for the deuterium compound probably because of greater coupling in the light molecule.

• Research Organization: Department of Chemistry, University of South Carolina, Columbia, South Carolina 29208
• NSA Number: NSA-33-002621
• OSTI ID: 4156102
• Journal Information: J. Chem. Phys., v. 63, no. 6, pp. 2303-2310, Journal Name: J. Chem. Phys., v. 63, no. 6, pp. 2303-2310; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

*DEUTERIUM-- ISOTOPE EFFECTS
400302* --Chemistry--Organic Chemistry--Isotope Effects
INFRARED SPECTRA
N40220* --Chemistry--Inorganic
Organic
& Physical Chemistry--Isotopic Effects
PHOSPHINES
RAMAN EFFECT
RAMAN SPECTRA