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COMMUNICATIONS TO THE EDITOR
VOl. 81
CONTROLLED FORMATION OF cis- AND transDECALIN-9-CARBOXYLIC ACIDS BY CARBONYLATION
carboxyl appears more crowded than a methyl group, which in analogous cases is known to reverse Sir: the usual order of stability and to favor the cisKoch and Haaf' have described the preparationof decalin system over t h e trans.2,3s485 In strong enough acid to make all the steps decalin-9-carboxylic acid (Soy0cis) from @-decalol, sulfuric and formic acids. I n a recent use of this reversible, equilibrium is approached; K = (V),' preparation, we have found t h a t products all t h e (117) = 4-1 1 at 5", depending upon the composition way from 84% cis (V) to 90% trans (IV) can be of the unisolated lOy0 of the material. This is obtained, the only variable being the amount of consistent with the value 1.5 at 250" obtained for fuming sulfuric acid included in t h e reaction 9-methyl-1-decalone. This work was performed under a grant from the medium (see Table I). National Institutes of Health. TABLE I COMPOSITIOS OF DECALIN-9-CARBOXYLIC ACID IS PREPARATIONS BY UNIFORM PROCEDURE 41.5 g. 98% H2SO4;4.6 g. 88% formic acid; 0-5", 1-13 hr. 30y0 oleum, g.
Sone
5 10 15 20 40 (Isomerization product)
% tvans (10.29 a)
70 cis (11.26 p )
90 74 56 19 5 7 5 9
10 22 5 41 62 5 84 79 87 5
loo-(% (%
cis)
lvans)
-
0 3 5 3 18 5
(2) W. E. Bachmann, A . Ross, 4 . S. Dreiding and P. A. S. Smith, J . Oig. Chem., 19, 222 (1951). ( 3 ) A. Ross, P. A. S. Smith and A. S . Dreiding, i b i d , 20, 905
(1955). (4) S . 1,. Allinger, ibid., 21, 915 (195G). ( 5 ) W. G. Dauhen and K. S. Pitzer in Newman, "Steric Effects in Organic Chemistry," John Wiley and Sons, N e w York, S . Y . , 1956, pp. 30, 31.
DEPARTMEKT OF CHEMISTRY RICHARD E. PIXCOCK UNIVERSITY ERNSTGRIGAT HARVARD PAULD . BARTLETT CAMBRIDGE 38, MASS. RECEIVED XOVEMBER 10, 1959
11 13 5
3 5 ON THE MECHANISM OF THE ENZYMATIC
DECARBOXYLATION OF ACETOACETATE' For the rapid assay of the total acid fraction calibration curves were prepared by the infrared Sir. examination of six synthetic mixtures of the puriI n order to investigate the mechanism of the enfied isomers (cis, m.p. 122"; trans, m.p. 135") a t zymatic decarboxylation of @-ketoacids,we have extotal concentrations of 25 mg. of acid per cc. of amined the oxygen exchange which accompanies carbon disulfide. Estimates made separately from the decarboxylation of acetoacetic acid, labeled in the "trans" peak a t 10.29 p and the "cis" peak a t the carbonyl group with 0'8, in the presence of the 11.26 agreed within 3% on isomer composition crystalline2 decarboxylase from Clostridium acetoof the products made with 0-10 g. of fuming sul- butylicum. furic acid present, b u t indicated the presence of Acetone was labeled with OI8 by allowing it to 1 1 1 8 z of a further isomer from the more strongly stand with enriched water (Stuart Oxygen Co., acid media. l.4yoO X 8 and ) a trace of sodium hydroxide. Ethyl X sample of the acid assaying 90Yo trans was acetoacetate was saponified in 2 ill potassium hyintroduced into a mixture of 41.5 g. of 9Sso sulfuric droxide in enriched water, and the potassium acetoacid and 20 g. of fuming sulfuric acid (3Oyo), acetate, labeled in the carbonyl and carboxyl groups, along with 5 g. of formic acid, over a period of 10 was obtained by evaporation i n nacuo and purified by minutes. After 1.5hours at 5" decalin-9-carboxylic precipitation of an alcoholic solution with ether. acid was recovered in 90% yield, having the com- The Ola content of the acetone was determined position 87.5 czs, 9yo trans. Thus kinetic control mass spectrometrically by measuring the ratio of the of carbonylation leads to trans-decalin-9-carboxylic 5s and GO peaks, using a Consolidated model 21acid, eventual equilibrium favoring the cis isomer. 103C mass spectrometer; the cracking pattern of Models show t h a t the trans-acyliuni ion IT, the acetone established its purity. Xcetone froin the enzymatic decarboxylation and from control co LOOII experiments was swept froin the reaction mixture with a stream of air through ;in ice-water COII,-,-\,,-.--z I/\ J +-. denser, and trapped a t - 78". ;1s;unple of acetone vapor then was prepared for illass spectrometry by II I\ equilibrating liquid and vapor a t 0". Some water undoubtedly was present in the liquid sample, but I \ < 0011 earlier work3has shown that, in the absence of buffers, exchange between acetone and water at low temperatures is very slow. The internal consist111 v ency of the results further supports this conclusion. Control experiments with potassium acetoacetate with the C-C=O+ atoms in a straight line, has were conducted by freezing the solution after 2.5 little axial-axial interaction and should be rapidly (1) This research w a s supported in part by a grunt from t h e Xstionxl formed without strain. On the other hand, in the trans acid IV, or its protonation product, the axial Institutes of Health.
c2J
17
+ k"L' >
eo
a7
(1) H Koch and W Haaf, Aizgeu. Chem , 70, 311 (1958), 261 (1'358).
.4>171 ,
618,
( 2 ) G. A . Hamilton and F. H. Westheimer, THIS J O U R S A L , 81,2277 (1959). (3) hI. Cohn and H. C. Urey, i b i d . , 60, 679 (1938).
