Condensed Phase Isotope Effects
作者:
W. Alexander Van Hook,
期刊:
Isotopenpraxis Isotopes in Environmental and Health Studies
(Taylor Available online 1968)
卷期:
Volume 4,
issue 5
页码: 161-169
ISSN:0021-1915
年代: 1968
DOI:10.1080/10256016808551993
出版商: Taylor & Francis Group
关键词: deuterium;isomers;tritium;vapour pressure;hydrogen;isotope effects
数据来源: Taylor
摘要:
It is well known that the condensed phase physical properties of molecular isotopic isomers are not the same. These differences in the vapor pressure, molar volume, surface tension, etc., are purely quantal phenomena. The effects are most exterme for isotopic substitution at hydrogen isotopes. Of the various physical properties which have been investigated the isotope effect on vapour pressure (VPIE) shows the largest ralative effects. In face, for hydrogen-deuterium substitution they range all the way from about inverse 2% per deuterium atom for nonpolar hydrocarbons (by inverse we mean that the molecule substituted with the heavier isotope has the higher vapor pressure) to as much as 20% normal (PH>PD) per deuterium atom for molecules which are strongle associated in the condensed phase. Such effects are about one order of magnitude larger than isotope effects which are observed in most systems on molar volumes, surface tension, etc. (Thus, for example, benxene at 20°C shows a rather small VPIE of 0.4% per atom D 3 but the molar volume effect is only 0.05% per D and the surface tension effect 0.03% [4].) This it would appear is the reason a majority of recent studies have been directed toward the VPIE. The emphasis in this paper reflects that trend and the balance of the discussion will deal almost exclusively with the vapor pressure isotope effect.
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