Boiling points of halogenated ethanes: an explanatory model implicating weak intermolecular hydrogen-halogen bonding.
This study explores via structural clues the influence of weak intermolecular hydrogen-halogen bonds on the boiling point of halogenated ethanes. The plot of boiling points of 86 halogenated ethanes versus the molar refraction (linked to polarizability) reveals a series of straight lines, each corresponding to one of nine possible arrangements of hydrogen and halogen atoms on the two-carbon skeleton. A multiple linear regression model of the boiling points could be designed based on molar refraction and subgroup structure as independent variables (R(2) = 0.995, standard error of boiling point 4.2 degrees C). The model is discussed in view of the fact that molar refraction can account for approximately 83.0% of the observed variation in boiling point, while 16.5% could be ascribed to weak C-X...H-C intermolecular interactions. The difference in the observed boiling point of molecules having similar molar refraction values but differing in hydrogen-halogen intermolecular bonds can reach as much as 90 degrees C.
Beauchamp
Guy
G
Department of Chemistry, Cégep de l'Outaouais College, 333 Cité des Jeunes, Gatineau, Québec, Canada J8Z 6M4. gbeauchamp@cegepoutaouais.qc.ca
D003198:Computer Simulation; D004980:Ethane / Q000031:analogs & derivatives* / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D012044:Regression Analysis; D044366:Transition Temperature
D006846:Hydrocarbons, Halogenated; D004980:Ethane