US EPA

8096167 

Journal Article 

Inclusion complexes of methylnaphthalenes 

Milgrom, J 

1959 

1 

Journal of Physical Chemistry
ISSN: 0022-3654 

63 

11 

1843-1848 

English 

10.1021/j150581a014 

A chance observation of an unaccountably high melting point prompted investigation of the system 2-methylnaphthalene-n-heptane. To confirm complex formation, this system was studied by regular and differential thermal analyses, vapor-pressure measurement, solids separation and X-ray analysis. Data have been represented by the usual linear phase diagram and a special logarithmic one. Six different complexes of 2-methylnaphthalene and n-heptane were found at temperatures between 25 and -92°. Depending upon temperature, eight moles of 2-methylnaphthalene combine with one, three or eight moles of n-heptane to form three pairs of complexes. The members of each pair have different crystal modifications. Transitions do not proceed readily; some complexes must be cooled below 0° before they transform and one is metastable. These results suggest a mechanism for complex formation. At room temperature a void apparently exists in the 2-methylnaphthalene crystal lattice, which can accommodate guest molecules of a definite shape. Complexes form with both straight- and branched-chain hydrocarbons, although molecules as long as n-hexadecane fail to react. Complex formation is not limited to 2-methylnaphthalene. 1-Methylnaphthalene and perhaps other polycyclic compounds also adduct paraffins. Below room temperature, a new realm of inclusion complexes probably exists.