Oct. 3 , 1955
HYDROLYSIS REACTIONS OF ETHYLENIMINES [CONTRIBUTION FROM THE METCALF
51 13
LABORATORIES, BROWNUNIVERSITY]
Reactions of Ethylenimines. V. Hydrolysis1 BY VIRGINIAB.
SCHATZ2 AND
LEALLYN B CLAPP
RECEIVED MARCH 28, 1955 Hydrolysis of 2,2-dimethylethyleniminein hydrochloric acid gave l-chloro-2-atni1~o-2-methylpropane (11) and l-arnino2-methyl-2-propanol ( I V ) in varying ratios depending on the temperature, concentration of acid and imine t o acid ratio. I n the special case of hydrolysis of 2,2-dimethylethylenimine picrate, water d o n e gave 954.t of amino alcohol (IVI and 12 A' hydrochloric acid gave 747, of chloroamine I1 and 125; of 2-chloro-l-amino-2-niethylpropane (111) The results are interpreted as due to competing S s l and S N 2 processes and this is supported by the nature of the products and kinetic data.
Hydrolysis of 2,2-dimethylethyleniminein dilute in sulfuric acid gave l-amino-2-methyl-2-propanol 65% yield as reported by Cairns.3 Other workers have agreed t h a t unsymmetrical ethylenimines open a t the tertiary4 (or secondary5) carbon rather than a t the primary with hydrolytic conditions. Gabriel and Ohle,6 on the other hand, reported t h a t hydrochloric acid, with 2-methylethylenimine gave 1-chloro-2-aminopropane (in 357, yield according to later work'). There is no conflict in these results. Strong acids such as sulfuric and picric are conjugated with weakly nucleophilic bases and are unable to compete with the solvent, water, in the ring opening. In the strong acid, hydrochloric, on the other hand, the conjugate base is strongly nucleophilic in comparison with water and a chloroamine is obtained as reported.6 Hydrochloric acid, therefore, appeared to be a felicitous choice of agents which could be used to study the competition between chloride ion and water in the ring opening of an ethylenimine. Such was the case. I n 6 iV hydrochloric acid an 85-907G yield of l-chloro-2-amino-2-methylpropane (11) (as hydrochloride) was obtained a t 2 5 O , a much higher yield than Smith and Platon' reported for the homolog. In 1 ;V hydrochloric acid a t looo,the competition was more nearly on even terms, for I1 was obtained in 45y0yield and l-amino-2-methyl-2-propanol (IV) in 39y0 yield. Other results of these hydrolytic reactions are summarized in Table I. The formation of these products is probably the resultant of two independent nucleophilic substitu. tions, one an S N 1 process and the other, S N ~None of the data found is in conflict with this interpretation. .As TarbelP has suggested in a similar case, formation of the amino alcohol IV would be favored by an SN1 mechanism since the intermediate tertiary carbonium ion (solvated or unsolvated) is energetically stable in comparison with the alternative primary carbonium ion. Conspicuous absence in the of the isomer, 2-amino-2-methyl-l-propano1, reaction mixtures under any of the conditions chosen for the hydrolysis supports the picture since (1) This work was supported in part by t h e Office of Ordnance Research Contract DA-19-020-ORD-592 a t Brown University. Presented before the Organic Division of the A . C. S. a t t h e 126th Meeting in New York, PI'. I?,, September, 1954. (2) Edwin P. Anthony Fellow, 1962-19X ( 3 ) T. L. Cairns, THISJOURNAL, 63, 871 (1941); R. Adams a n d T . L. Cairns, ibid., 61, 2164 (1939). (4) K. N. Campbell, B. I(. Campbell, J. F . McKenna and E. P. Chaput, J . Org. Chem., 8, 103 (1943). ( 3 ) F. Wolfheim, B e y . , 47, 1440 (1914). (0) S . Gabriel a n d H. Ohle, ibid.. 6 0 , 804 (1917). (7) I,. Smith a n d B. Platon, ibtd., 66, 3143 (1922). (8) D. S . Tarhell and P. Sohle, Jr., THIS J O U R N A L '72, , 2657 (1950).
TABLE I
HYDROLYSIS OF
2,2-DIMETHYLETHPLESIMINE IS HYDRO-
Concn. acid,a of. Temp.. I1 4.\-
1 1 1 1 1 6
O C .
0 25 35 62 100
CHLORIC Yields, %
ACID I1
IVJ
IIIb
IIC
70" 63.4 61.2 58.5
16' 66 28
x
1 0Rates 3 , I V X IOJ,
mm-1
0.0130 0.44
min.-'
(Halfreaction, hr.)
0.0059 0.25 1.17 22
570 16
.. 1.S.i :j ,;, 31 31 0.25 45 39 25 90 4 85 1 . 3 3 . 1 0.36 3 Acid: imine = 3 : 1. * Yield of l-chloro-2-~mino-2methylpropane (11) and 2-chloro-1-amino-2-methylpropane (111)by titration. The yield of compound 111is negligible. Yield of pure l-chloro-2-amino-2-methylpropane(11) by isolation. Yield of l-amino-2-methyl-2-propanol determined as p-bromobenzenesulfonamide. Approximately 75oj, of correct value (see Experimental). e Yield ca1culatt.d from {he half-reaction.
--+CH,
CH?
CH, >c
