Normal boiling points of 1,ω-alkanedinitriles:: The highest increment in a homologous series

The normal boiling point for cyanogen is -22 degrees C; for its next homologue, malononitrile, it is 219 degrees C. The difference of 241 degrees C is apparently the highest one encountered for the addition of a single methylene group. Problems connected with boiling points and a rationalization for this observation are discussed in the context of intermolecular forces for liquids. A quantitative structure-property relationship (QSPR) study of the normal boiling points for monohaloalkanes and for the corresponding nitriles is reported. The behavior of the nitrile group as a pseudohalogen is also discussed. Normal boiling points of compounds having a cyano group bonded to an electron-attracting substituent situate the CN group close to being a pseudohalogen, but when the CN group is bonded to electron-donor substituents, the situation changes.