RELATIONS BETWEEN THE BOILING POINTS OF PERFLUORO-ETHERS, PERFLUOROALKANES AND NORMAL-ALKANES

The boiling points of linear and cyclic mono- and poly-perfluoro-ethers containing n carbon and m oxygen atoms can be estimated as being equal to the boiling point of perfluoroalkanes of chain length (n + m) less m(22 - m), independent of whether the ether is branched or cyclized. Deviations from a smooth increase in boiling point with molecular mass can occur when ethers close in molecular mass have different structures. The non-available boiling points of the higher perfluoroalkanes have been estimated from the relationship T(F) = 0.247T(H) X M(F)/M(H) where T(F) and T(H) are the respective absolute boiling points of a fluoroalkane and the corresponding normal alkane with masses of M(F) and M(H). The limiting boiling point for the fluorocarbon series derived from this relationship is 899 K.