Degree Name

Master of Science (MS)

Semester of Degree Completion

1975

Thesis Director

Giles Henderson

Abstract

Dipole moment measurements have been carried out on 2,3-butanedione in solution, pure liquid, and the vapor phase. A dipole moment of 1.03 ± .01 Debye was observed for dilute solutions of 2,3-butanedione in carbon tetrachloride. Pure liquid samples exhibit an anomalous dipole of 1.56 ± .01 Debye. The following results were obtained for vapor phase measurements: 1.04, 1.07, 1.08, 1.11, and 1.17 ± .01 Debye at 310.15, 350.15, 370.15, 431.70 and 472.10 ± .02°K respectively.

The acetyl torsional potential was characterized from the observed temperature dependence of dipole moment. This torsional mode was described by a two-parameter potential function: V(Ø) = V1/2 (1-cosØ) + V2/2 (1-cos2Ø) where Ø is the acetyl torsional angle. The temperature dependence of the dipole moment was analyzed using statistical thermodynamic methods to determine the internal rotation potential parameters V1 and V2. A numerical least squares fit of the data yields V1=2890 ± 30 cm-1 (8.26 ± .09 Kcal or 34.6 ± .3 KJ) and 0.0-1.

A two parameter potential function has been employed for the first time to characterize the temperature dependence of the dipole moment. The results of this study indicates that in contrast to glyoxal, the cis isomer of 2,3-butanedione is unstable, and accounts for the failure of other experimental methods to observe this isomer.

Download

Included in

Chemistry Commons

Share

COinS