Structural Effects in the Vapor Pressures of Isotopic Molecules. O18and N15Substitution in N2O

摘要

The relative vapor pressure ratios of the isotopic N2O molecules have been determined by distillation in a column under total reflux. It is shown that the vapor pressures are in the sequenceN14N14O16N14N15O16N15N14O16N14N14O18.The absolute vapor pressure ratios have been determined from the kinetic behavior of the column and the decrease in separation by production from the column.Theoretical calculations of the relative vapor pressure ratios can be made from the atomic masses and the random structure of liquid N2O. The calculated relative isotope effects are in good agreement with experiment. The absolute value of lnPN14N14O16sol;PN14N15O16is calculated from the specific heat of N2O to be 8.2times;10mdash;4at 184deg;K, in good agreement with the experimental value7.8plusmn;1.4times;10minus;4. The difference in vapor pressures of the isotopic isomersN14N15O16andN15N14O16is attributed to hindered rotation of the molecule in the liquid.