The Cyclization of Alkyl Side Chains of Naphthalenes: The GC/Potential Energies/FTIR Approach


Gas chromatographic measurements of the retention times of alkyl naphthalenes on packed columns with polar and non-polar stationary phases have proven that the logarithm of the relative retention time increases bi-linearly (not linearly) with the number of carbon atoms in a molecule. This is caused by a strong inclination of alkyl side chains toward intramolecular cyclization. A FTIR spectral analysis has shown that longer alkyl side chains of alkyl naphthalenes are cyclized through an interaction between the terminal CH3 group and the aromatic ring. Conventional aromatic-aliphatic molecules thus become new molecules with quasi-alicyclic rings. This, however, alters the effect of non-covalent van der Waals attractive forces both inside and outside the molecules, which is reflected in an exponential increase of the retention times of alkyl naphthalenes with a side chain longer than propyl and in the bi-linearity of the logarithmic dependence of the relative retention times on the number of carbons in the molecule.

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Straka, P. , Novotná, M. , Buryan, P. and Bičáková, O. (2014) The Cyclization of Alkyl Side Chains of Naphthalenes: The GC/Potential Energies/FTIR Approach. American Journal of Analytical Chemistry, 5, 957-968. doi: 10.4236/ajac.2014.514103.

Conflicts of Interest

The authors declare no conflicts of interest.


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