Formation of Bisnitrosocyclohexaneand Cyclohexanone Oxime by Silent Electric Discharge John H. Wagenknecht Central Research Department, Monsanto Co., St. Louis, Mo. 63166
Cyclohexane reacts with compounds which produce NO' on ionization to form nitrosocyclohexane. Examples of reactants are NO, alkyl nitrites, or nitroalkanes. When the reaction is carried out above lOo"C, the bisnitrosocyclohexane i s rearranged in situ to cyclohexanone oxime. The yield of bisnitrosocyclohexane i s not affected by wide ranges of gas diluent flow rates. Important variables are pressure, temperature, power density, reactant ratio, and reaction zone length.
There finding because which,
has been considerable interest in recent years in new routes to bisnitrosocyclohexane (BNCH) it can be rearranged to cyclohexanone oxime in turn, can be converted to caprolactam.
Nitrosation of cyclohexane is carried out commercially by the Toyo Rayon Photonitrosation process (Banciu, 1966). Other reported methods of nitrosating cyclohexane include the photochemical reaction with NO (Strausz and Gunning, 1963) or alkyl nitrites (Mackor et al., 1969; Mackor and DeBoer, 1970), electron beam irradiation (Burrell, 1962; Taylor, 1962), and radiolysis (Milhaud and Durup, 1962). I t was reported recently (Fuhrman et al., 1969) that the reaction of NOC1 and cyclohexane could be initiated by an electrical discharge rather than by photolysis. These workers found further that NO would react with cyclohexane in the discharge to form BNCH. The reaction of NO and cyclohexane to form BNCH also was observed in our laboratories. I n addition, species which formed NO. on ionization-e.g., R O N 0 or RNO2would react with cyclohexane in the discharge to form BNCH. The NO-cyclohexane reaction was studied to determine the effects of reaction variables on the yield of BNCH. Experimental
The apparatus used was either of the two modified Siemens ozonizers shown in Figures 1 and 2. Gas flow was measured with RGI (F-1100 and F-1200) rotameters (Cole-Parmer Instrument & Equipment Co., Chicago, Ill.) Power density was automatically maintained a t a predetermined level with the powerstat shown in Figure 3. All experiments were carried out using 60-cycle ac current. Technical grade NO (98.55)was obtained from Matheson and used as received. Cyclohexane (C-556) was obtained from Fisher Scientific Co. Cyclopentane, cyclo184
Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 2, 1971
heptane, and cyclooctane were obtained from Aldrich Chemical Co. The following reagents or authentic samples were prepared according to previously reported methods: methyl nitrite (Yoffe and Gray, 1951); t-butyl nitrite (Noyes, 1943); BNCH (Okamura and Sukurai, 1952); cyclohexyl nitrate (Titov and Matveeva, 1953). The cycloalkanone oximes were prepared by reaction of the corresponding ketones with hydroxylamine. Analysis. I n experiments in which no cyclohexanone oxime was formed, the BNCH was determined polarographically. The reaction product was stripped t o near dryness on a rotary evaporator to remove cyclohexane, dichloromethane (used to wash product from the reactor), and other volatile components. The product was then diluted to a known volume with benzene and extracted with dilute aqueous NaOH. An aliquot of the benzene solution (generally one ml) was added to 25 ml of 50% EtOH containing 0.1M HC1. This solution was analyzed polarographically determining the concentration of BNCH from the diffusion current of the wave a t E , = -0.38 V vs. saturated calomel electrode. Nitrocyclohexane and cyclohexyl nitrate do not interfere. In reactions in which only cyclohexanone oxime was formed, analyses were carried out by gas chromatography. A two-ft, >
