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National Advisory Committee for Aeronautics, Technical Notes - Synthesis, Purification, and Physical Properties of Hydrocarbons of the Naphthalene Series I

The synthesis, the purification, and several physical properties
of four l-alkylnaphthalenes, l-methylnaphthalene, l-ethylnaphthalene,
l~butylnaphthalene, and l~isobutylnaphthalene, are described. In each
case, the hydrocarbon was synthesized from l-naphthylmgnesimn bromide
by well-known methods. The final hydrocarbons (a minimum of 2000 ml
each) were purified by fractional distillation through 6-foot Podbiel—
niak columns to obtain 500 milliliters of each hydrocarbon with a
calculated purity higher than 99 mole percent. The physical properties,
determined for material having a calculated purity of 99.8 mole percent
or higher, include melting point, boiling points at 760 millimeters of
mercury, index of refraction, density at 20° C, kinematic viscosity at
four temperatures, heat of fusion, and heat of combustion. Time—
temperature melting curves and infrared spectra are presented for the
four l-alkylnaphthalenes.

As part of an investigation of the effect of molecular structure
on the physical properties of hydrocarbons, a series of alkylnaphtha-
lenes and their hydrogenated derivatives is being prepared at the NACA
Lewis laboratory. The synthesis program was necessary because of the
relative scarcity of complete and reliable data in the literature.

Almost all the literature on the alky’lnaphthalenes describes
attempts to separate the individual hydrocarbons from mixtures of
isomers or from natural products such as petroleum (reference 1) or
coal—tar distillates (references 2 and 5). In order to obtain products
of 1mm structure and purity, direct synthesis of the desired hydro-
carbons appeared to be a preferable approach.

The synthesis of l-methylnaphthalene by the hydrolysis of
l—naphthylmethylmagnesium chloride has been reported (reference 4).
The condensation of dimethyl sulfate with l—naphthylmagnesium bromide,
as suggested in reference 5, was chosen for this preparation.

l-Ethylnaphthalene has been prepared by the reduction of methyl-
l-naphthyl ketone (references 6 to 9), by the condensation of
l-naphthylmagnesium bromide with diethyl sulfate (reference 5) or
ethyl—p—toluenesulfonate (reference 10) , and by the reaction of
l—naphthylmethylmagnesium chloride with dimethyl sulfate (reference 11) .
The reaction of diethyl sulfate with l-naphthylmagnesium bromide was
used herein.