Internal rotation in ethylamine: A treatment as a two-top problem

Journal Article · Mon Dec 15 04:00:00 EST 1975 · J. Chem. Phys., v. 63, no. 12, pp. 5177-5189

DOI:https://doi.org/10.1063/1.431300· OSTI ID:4097257

Tsuboi, M; Tamagake, K; Hirakawa, A Y; Yamaguchi, J; Nakagawa, H; Manocha, A S; Tuazon, E C; Fateley, W G

The infrared absorption spectra of eight isotopic ethylamine molecules, i.e., CH$sub 3$CH$sub 2$NH$sub 2$, CD$sub 3$CH$sub 2$NH$sub 2$, CH$sub 3$CD$sub 2$NH$sub 2$, CD$sub 3$CD$sub 2$NH$sub 2$, CH$sub 3$CH$sub 2$ND$sub 2$, CD$sub 3$CJ$sub 2$ND$sub 2$, CH$sub 3$CD$sub 2$ND$sub 2$, and CD$sub 3$CD$sub 2$ND$sub 2$, have been examined in the vapor phase in the 300--100 cm$sup -1$ region. Several Q-branch peaks were observed for each isotopic species and assigned to the torsional oscillations of the methyl and amino groups of the trans and gauche isomers. The energy levels were calculated on the basis of a coupled two-top system. The analysis yielded a probable potential function for the internal rotation about the C--N bond of the form V ($alpha$) = (316.5/2)(1-cos$alpha$)- (11.3/2)(1-cos2$alpha$)+(713.7/2)(1-cos3$alpha$) -(25.0/2)(1-cos4$alpha$)+(25.0/ 2)(1-cos5$alpha$)-(3.7/2)(1-cos6$alpha$). The difference between the potential energy minima of the trans and gauche conformations is about 230 cm$sup -1$, the trans being the more stable form. It has been concluded that the axis of internal rotation of the amino group does not coincide with the N--C bond but is along a line about 4.5degree from the N--C bond and in the plane bisecting the NHH triangle. (AIP)

• Research Organization: Faculty of Pharmaceutical Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-014288
• OSTI ID: 4097257
• Journal Information: J. Chem. Phys., v. 63, no. 12, pp. 5177-5189, Journal Name: J. Chem. Phys., v. 63, no. 12, pp. 5177-5189; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

*DEUTERIUM-- ISOTOPE EFFECTS
400302* --Chemistry--Organic Chemistry--Isotope Effects
AMINES
ELECTRONIC STRUCTURE
INFRARED SPECTRA
N40220* --Chemistry--Inorganic
Organic
& Physical Chemistry--Isotopic Effects
ROTATION