Correlations between the crystalline long c-parameter and the number of carbon atoms of pure n-alkanes

Linear relationships of variations of crystalline c-parameters of orthorhom bic, triclinic and monoclinic n-alkane structures as a function of n, the c arbon atom number, are established by linear least square fitting the data taken from the literature and compared with the relationships previously de termined. In particular, the results correspond well with the predictions o f Nyburg and Potworowski for Pbcm orthorhombic structures: they allow the p recise determination of the mean carbon-carbon distance projected onto the chain axis that is equal to 1.2724 Angstrom and the gap value of 3.1476 Ang strom between the end-methyl-group carbon atom planes of the two consecutiv e molecule layers. (C) 1999 Elsevier Science Ltd. All rights reserved.