Boiling Points of the Family of Small Molecules, CHwFxClyBrz: How Are They Related to Molecular Mass?

• Michael Laing ^[1]
  1. [1] University of Natal, South Africa
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 78, Nº 11, 2001, pág. 1544
• Idioma: inglés
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• Resumen

  • A plot of boiling point versus molecular mass for the family of tetrahedral molecular compounds CHwFxClyBrz is not linear, but yields a two-dimensional array with the data for molecules of similar formulae lying on straight lines. A plot of boiling point versus molar refraction (polarizability) of the compounds gives three near-parallel straight lines. The highest is for the family of compounds CH2XY; the lowest is for the all-halogen compounds CFxCyBrz; the compounds CHXxYyZz and CH3X lie intermediate. The boiling points of the compounds containing hydrogen are enhanced relative to what their molecular refraction suggests (excepting CH4). Boiling point is related to the macroscopic properties of refractive index and density of the liquid and to the molecular properties of molar refraction and dipole moment. These are connected by the molecular mass, which, with the density, determines the molar volume and thus the polarizability.