Elucidation of liquid-force fields in methyl fluoride by means of vapor-pressure isotope effects. [/sup 12/CH/sub 3/F, /sup 13/CH/sub 3/F and /sup 12/CD/sub 3/F]

Technical Report · Fri Jan 01 04:00:00 EST 1982

OSTI ID:5318328

Shulman, J; Ishida, T

The vapor pressure isotope effects (VPIE) of the three isotopic methyl fluorides: /sup 12/CH/sub 3/F, /sup 13/CH/sub 3/F, and /sup 12/CD/sub 3/F, were studied using differential manometry and a precision cryostat. Absolute pressures were measured using a spiral quartz gauge, and differential pressures were obtained by use of capacitance gauges. The gases were purified to better than 99.995% by preparative gas chromatography and a gas-solid adsorption system. Vapor pressures were measured between 132.52/sup 0/K and 213.12/sup 0/K which correspond to the pressures of 3.712 and 1887.1 torr. Analysis of the vapor pressure data revealed an inverse isotope effect (ln(f/sub c//f/sub g/) < 0) for the /sup 12/CH/sub 3/F//sup 13/CH/sub 3/F isotopic pairs and a normal effect (ln(f/sub c//f/sub g/) > 0) for the /sup 12/CH/sub 3/F//sup 12/CD/sub 3/F isotopic pairs. A series of calculations using Wilson's FG-matrix method and a modified Schachtschneider-Snyder program resulted in a temperature-dependent internal-external interaction in the condensed phase: A strongly temperature-dependent internal-external interaction between the C-F stretching motion and a translation motion in the direction of its figure axis is necessary to explain the observed isotopic vapor pressures.

• Research Organization: City Univ. of New York, NY (USA); State Univ. of New York, Stony Brook (USA)
• DOE Contract Number: AC02-80ER10612
• OSTI ID: 5318328
• Report Number(s): DOE/ER/10612-7; ON: DE82014663
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical &amp; Physicochemical Properties-- (-1987)
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
CARBON 13
CARBON ISOTOPES
CHROMATOGRAPHY
CONTROL EQUIPMENT
CRYOSTATS
DESIGN
DEUTERIUM
EQUIPMENT
EVEN-ODD NUCLEI
FLUIDS
FLUORINATED ALIPHATIC HYDROCARBONS
GAS CHROMATOGRAPHY
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
LIQUIDS
LOW TEMPERATURE
MEASURING INSTRUMENTS
METHYL FLUORIDE
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHYSICAL PROPERTIES
PRESSURE GAGES
PURIFICATION
SEPARATION PROCESSES
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
THERMOSTATS
VAPOR PRESSURE