was also 10-4 M in leuco crystal violet and 2 X 10~1 234 M in toluenesulfonic acid. From the amount of crystal violet dye obtained as determined spectrally, and from the reaction stoichiometry (1 mol of dye per biimidazole dissociated) and quantum yield of unity,9 both experimentally determined, radical concentration immediately after the flash was obtained.Rates of Triarylimidazolyl Radical Dimerization.-A Perkin-Elmer "Spectrachord" Model 400A was set up in a dark room to record absorbance (at of each radical) vs. time. A solution of biimidazole in carefully purified benzene was irradiated until a steady state was established and absorbance was recorded for several half-lives and determined eventual!)-at "t = ® ." From the usual second-order expression, the slope of 1/A. plotted vs. t gave k/e (cell length = 1 cm) reported in Table I. From these values k was calculated.Extreme care was necessary to free solvents of impurities which react with radicals. Normally, three distillations of reagent grade solvent sufficed. Even with carefully purified solvents, radical dimerization was not the exclusive fate of radicals in the media studied. A small but detectable deviation from strict second-order was apparent sometime during the second half-life4 and A" was slightly greater than A measured prior to irradiation. Rate constants were taken from the first half-life.Rates in 50:50 vol methanol-benzene were measured both in the spectrometer and in the flash photolysis apparatus used to determine extinction coefficients. An oscillographic trace of absorbance vs. time was photographed.

Biophysics, for the use of laboratory facilities and for salary and computer support. Thanks are also due to the Mental Health Board of Alabama for partial financial assistance.

A consideration of the mechanism of the ester cleavage reaction suggests that methyl crotonate would be much morc susceptible than methyl 8-bromobutyrate to reaction with hydrogen bromide.The Kinetic Studies.-For the optical rotation studich samples of the pure bromoesters were sealed in small Pyrex glass tubes. The tubes had previously been exposed for 24 hours to hot concentrated nitric acid, washed with distilled water, dried and stored in a desiccator over phosphorus pentoxide. The rate samples were immersed in the

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minutes, and a pinch of urea was added to destroy any excess nitrous acid. This solution of the diazonium salt was added with stirring to a cold solution of 12.8 g. (0.13 mole) of freshly prepared cuprous chloride in 120 ml. of concentrated hydrochloric acid, and the resulting mixture was stirred until it reached room temperature and then warmed on a steam-bath for fifteen minutes. It was extracted with three 500-ml. portions of benzene, and the benzene extracts were washed with water, with several portions of 0.25 N sodium hydroxide solution, and again with water. The benzene was eva orated and the residue distilled (b.p. 130-150' (1-2 mm.)y to give 14.2 g. (50% yield) of crude 4chloro-5-methoxyacenaphthene. After several crystallizations from methanol, material melting a t 84-86' was obtained.Anal. Calcd. for ClsHIIC10: O C H s , 14.2; C1, 16.2. Found: OCHs, 14.0; C1, 16.1.B. From 4-Chloro-5-acenaphthenol (V) . -A solution of 2.05 g. (0.01 mole) of 4-chloro-5-acenaphthenol and 0.6 g. of sodium hydroxide in 25 ml. of water was treated with dimethyl sulfate a t 80' in an atmosphere of nitrogen. A total of 2.86 g. (0.0227 mole) of dimethyl sulfate was added in 1.52, 0.67, and 0.67 g. portions a t ten-minute intervals, interspersed with the addition of three 2-ml. portions of 2.5 N sodium hydroxide. After an additional twenty minutes a t SO' , the reaction mixture was extracted with benzene, and the benzene was washed with water and evaporated.Distillation of the residue gave 1.2 g. (55%) of solid material that melted a t 84-86' after crystallization from methanol. A mixed melting point determination with authentic 4-chloro-6-methoxyacenaphthene prepared above showed no depression.Ether Cleavage of 4-Chloro-5-methoxyacenapbthene (=).-A mixture of 1 g. of XI, 8 ml. of glacial acetic acid, and 4 ml. of 48% hydrobromic acid was heated under reflux in a nitrogen atmosphere for four hours. It was then poured into 25 ml. of water and extracted with three 25-ml. portions of chloroform. The chloroform extracts were washed with three 25-ml. portions of 0.5 N sodium hydroxide and, after acidification, the combined aqueous extracts were re-extracted with three 25-ml. portions of chloroform. After washing with sodium bicarbonate solution and drying, the chloroform was evaporated and the residue sublimed at 80' (0.05 mm.). The sublimate was 5-acenaphthenol (50 mg., 6.5% yield), m.p. 125-126', no depression on admixture with an authentic sample.When 1 g. of 4-chloro-5-methoxyacenaphthene was heated with 3 g. of pyridine hydrochloride according to the procedure by Prey," the reaction product, isolated as above, consisted of 230 mg. (30%) of 5-acenaphthenol, m.p. 125-126'.A comparison has been made of the conjugate addition of ethyl, isopropyl and l-butyl Grignard reagents to 2-cyclohexenone and its open chain analogs, 3-penten-2-one, 3-hexen-2-one, 3-hepten-2-one and 4-hexen-3-one. Except for the addition of ethylmagnesium bromide, the amount of conjugate addition to 2-cyclohexenone is comparable to the amount of conjugate additi...