Laser-induced nitration

Abstract

Infrared laser-induced production of nitrated products is achieved by irradiating compounds selected from propane, n-butane, isobutane, n-pentane, and cyclopropane in the gas phase while in a stainless steel cell 5.times.5.times.10 cm equipped with zinc selenide windows to admit the infrared laser radiation in the range of 10.4 or 9.4 micrometers provided by a continuous wave CO.sub.2 laser. KC1 windows on the short path are to monitor infrared spectra of reactants and products. Nitrogen dioxide or nitric acid is present as the second reactant and the nitrating agent. The infrared laser-induced method far exceeds the yield of nitrated products found in the argon-ion laser-induced nitration of isobutane reported in the literature. Applicants' method at least equals the yield from thermally activated systems with a minimum formation of undesirable side products. A representative sample, 220 torr of gaseous butane, and 20 torr NO.sub.2 is irradiated in one experiment for 30 seconds with 75 W/cm.sup.2 at a frequency of 956 cm.sup.-1. About 40% of the NO.sup.2 is converted to nitrocompounds. Identified as nitro-products are nitromethane, nitroethane, 1-nitropropane, 1-nitrobutane and 2-nitrobutane. More than 60% of the nitro-products are in the long chain forms, 1-nitrobutane and 2-nitrobutane. Pressure of the NO.sub.2 reactant range from about 20 to 30 torr while the hydrocarbon reactant pressure range from about 200 to about 500 torr. Irradiation times ranges from about 30 to about 60 seconds. Laser powers range from 75 watts/cm.sup.2 to about 82 watts/cm.sup.2.