Vapor pressure isotope effects in liquid methyl fluoride
The vapor pressures of the isotopic methyl fluorides /sup 12/CH/sub 3/F, /sup 12/CD/sub 3/F, and /sup 13/CH/sub 3/F have been measured at temperatures between 132.48 and 213.12 K by differential manometric techniques in a precision cryostat. Throughout the whole temperature range of the measurements, P(/sup 12/CH/sub 3/F) > P(/sup 12/CD/sub 3/F) and P(/sup 12/CH/sub 3/F) < P(/sup 13/CH/sub 3/F). The data are best represented by T ln (f/sub c//f/sub g/) = (2225.2 +- 7.4)/T - (4.444 +- 0.046) for the D/H effect and by T ln (f/sub c//f/sub g/) = (56.58 +- 2.09)/T - (0.6383 +- 0.0133) for the /sup 13/C//sup 12/C effect. A series of calculations using Wilson's GF matrix method and a modified Schachtschneider-Snyder program resulted in temperature-dependent internal-external interactions in the liquid phase: Presence of such interactions between the molecular translation in the direction of the molecular figure axis and the parallel normal modes nu/sub 2/ and nu/sub 3/ is a necessary requirement for satisfactory explanation of all isotopic vapor pressure and spectroscopic data of the liquid. The specific internal-external interactions found are consistent with the structure of CH/sub 3/F clusters obtained by ab initio molecular orbital calculations. 5 figures, 8 tables.
- Research Organization:
- State Univ. of New York, Stony Brook
- DOE Contract Number:
- AC02-80ER10612
- OSTI ID:
- 5559179
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 87:16
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON 13
ISOTOPE EFFECTS
DEUTERIUM
METHYL FLUORIDE
CONFIGURATION INTERACTION
STRUCTURAL CHEMICAL ANALYSIS
VAPOR PRESSURE
CRYOSTATS
DEUTERIUM COMPOUNDS
EXPERIMENTAL DATA
INTERMOLECULAR FORCES
LOW TEMPERATURE
MASS SPECTRA
MOLECULAR ORBITAL METHOD
MOLECULAR STRUCTURE
TEMPERATURE DEPENDENCE
CARBON ISOTOPES
CONTROL EQUIPMENT
DATA
EQUIPMENT
EVEN-ODD NUCLEI
FLUORINATED ALIPHATIC HYDROCARBONS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHYSICAL PROPERTIES
SPECTRA
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
THERMOSTATS
400302* - Organic Chemistry- Isotope Effects- (-1987)
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)