The Rearrangement of 1,l-Dimethyl-l-Phenacyihydrazinium Bromide Following a recent article in this Journal,' we now descrihe the remarkably facile rearrangement of (I) to (111) as a safe, . ~ photoinduced decomposition of (I) is of topical practical undergraduate experiment illustrating the chemistry of y l i d ~The interest3 to the Stevens and related rearrangements.
The formation of (111) may he understood in terms of a Wawzonek rearrangement of the aminimide (derived from (I))4 to (II), theexpected product of the rearrangement. Themild condition oftherearrangement of (I) to (11) supports theview that the pendant carbonyl group of the phenacyl suhstituent assists in generation of the aminimide.2 The suhsequentfragmentation of (11) to dimethylamine and phenylglyoxaldimine followed by dehydrative self-condensation of the latter would then yield (In).
Experimental CAUTION. Great rare should he exercizrd in using hoth phenaryl brom~deand 1.1-dimethylhydrarine. Phenavyl bmmirl~1s a p,tenf lnrhrymafor and should be weizhed and handled m the h d . Spilling either chemical on the hnndr ahuuld he avoided. I,l-Dimethyl-l-Phenncylhydrazinium Bromide (I). A solution of 20.06 g (0.10 mole) of phenacyl bromide and of 6.11 g (0.10mole) of 1,l-dimethylhydrazine in 100 ml of absolute ethanol was allowed tostand in the freezer overnight. Filtration gave 24.4 g (94%) of (I), mp 122-124°C, as a snow-white microcrystals. This material is sufficiently pure for the next step. Thermal Rearrangement of (I). A solution of 5.20 g (0.02 mole) of (I) in 50ml of n-propanol was gently heated to reflux for 1.25 hr. Boiling benzene (100 ml) was added to the dark residue obtained after evaporation of the solution. After cooling, the insoluble solid (dimethyla'mine hydrobromide) was filtered and washed with hot benzene. The combined filtrate was heated to boiling, treated with Norit, filtered hot and evaporated to dryness in vacuo to give 2.20 g (88%)of (III), mp 161-165*. Recrystallization from ethanol-benzene gave a 50% yield of (III), mp 190-191°.5 Pkotolytic Rearrangement of (I). A solution of 5.ZOg (0.02 mole) of (I) in 60mlof methanol was irradiated in a 125-ml Erlenmeyer flask with stirring for four daysusing aGates 420 U-l Model uv lamp. After evaporation of the solvent, theresulting yellow solid was stirred with 50ml of water and the insoluble solid (111) was collectedand driedto yield 1.55 g (62%) of solid, mp 150-160". Recrystallization from ethanol-benzene gave 1 . 0 0 (40%) ~ of (III), m p 185-189°.5 Maytum, D., and Keene, B. R. T., J. CHEM. EDUC., 49,215 (1972). Koga, M., and Anselme, J.-P., Chem. Comm., 53 (1973). There is a misprint in this reference; instead of n-pentyl alcahol, read n-propanol. V i n e , S. H., J. CHEM. EDUC., 48.99 (1971). McKillip, W. J., Sedor, E. A,, Culhertson, B. M., and Wawzonek, S., Chem. Reus., 73,255 (1965). The reported mp of (111) is 198-199".2 However, it is very difficult t o obtain sample having this mp without several recrystallizations. 2
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M. Koga Central Research Institute of Teijin Tokyo, J a p a n
A. P. Stamegna D. J. B u r k e J.-P. Anselme University of Massachusetts a t Boston Boston, 02125
Volume 54, Number 2,February 1977 1 111
