March 5 , 1960
COMMUNICATIONS TO THE E D I l O R
1255
I n a typical experiment, 3.0 g. of D-(+)-Nacetyl-C 1 4 - 1 ,2,2-tri~henylethylamine,~ [ a] 2 5 ~ 109" (dioxane) (molar radioactivity, 7.941 mc. carbon-14) was converted to 3.15 g. of D-(-)-11, [ A l Z 5 ~ 320" (benzene), by the method of France, Heilbron and Hey.6 The material could not be obtained free from contaminating amide, as efforts t o crystallize the sample resulted in its decomposition. LV F. EDGELL Carbon and hydrogen determinations gave variable, RICHARD B ]VETHERILL LABORATORY J. HUFF PURDUE USIVERSITY J . THOMASunsatisfactory results. The purest sample obLAPAYCTTE, IXDIASA 13. LEHMAN tained exhibited a molecular weight of 343.5 + C ANCELL 1.3 (calcd. 344.4), as determined by radioactivity G. ASATO assay. A solution of 2.12 g. of D-(-)-I1 in 200 RECEIVEDDECEMBER 18, 1959 ml. of acetic acid was kept a t 40.5' until reaction was complete, as shown b optical rotation of the solution. Samples of (+r-III and (+)-I11 were A RADIOCHEMlCAL CRITFRION FOR obtained by fractional crystallization of the product CONFIGURATIONAL RELATIONSHIP Sir: from 95% ethanol, and their purity was checked by I t has been shown' that h--nitrosoamides undergo infrared analyses. The sample of (+)-I11 showed thermal decomposition in polar and in non-polar on radioactivity assay 3.353 mc. carbon-14 per solvents with net retention of configuration. T o mole, whereas the (+)-I11 showed on radioactivity our knowledge, however, such decompositions have assay 2.168 mc. per mole, allowing the calculation not yet been used as criteria for configurational that (-)-I11 contained 0.982 mc. of carbon-14 per relationships. In connection with studies of the ~ n o l e . ~ . ~ . * stereochemical course of the deamination of 1,2,2Acknowledgment.-The authors wish t o actriphenylethylamine (I), it became necessary to knowledge the encouragement and support given relate the configuration of (+)-I with that of (+)- J. €3. C. by the late Professor Cash B. Pollard of the 1,2,2-triphenylethano1[(+)-IV].' In order that University of Florida. the N-nitrosoamide decomposition could be used cinimide and alkaline hydrolysis IC. J. Collins, unpublished work]. for this purpose, additional verification of its stereo- T h e (+)-glycol is obtainable from D-(-)-mandelic acid by treatment with phenylmagnesium bromide [A. McKenzie and H . Wren. J. Chem. chemical course in the decomposition of (-)-N.SOL.. 97, 473 (1910)], and the absulute configuration of mandelic acid acetyl-X-nitroso-l,2,2-triphenylethylamine [ (-)-I1 ] has been established by Mislow [ K . Mislow. THISJ O U R N A L , 73, 3954
(C0)j- resembles the spectrum of Fe(C0)6 and might indicate a similar structure. The spectrum of HFe(C0)4- correlates nicely with those of Fe(C0)4= and HzFe(C0)4. The decrease in niolecular symmetry with addition of hydrogen is clearly evident. Professor T. Richardson is thanked for helDful discussions l n orbital theory.
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was necessary. In combination with appropriate tracer studies, such verification now has been obtained. Thus, D-( -)-11, labeled with carbon-14 in the acetyl group, was prepared froin D-(+)-I, and thermally decomposed in purified acetic acid at 40.5'. The product, consisting of 7070 (+)-I11 and 30% (-)-III, was fractionally crystallized and each fraction [(+) and ( + ) I was assayed for carbon-14. It was shown that (+)-I11 contained 29.2% of the carbon-14 originally in D-(-)-11, whereas (-)-I11 contained only 3.37, of the original radioactivity. I n a repetition of this experiment with D-(+)-11, (-)-I11 contained 29.5% and (+)-I11 3.7% of the original carbon-14. Since the labeled acetate group in I1 should be expected to remain preferentially in the same configuration during the decomposition t o 111, whereas solvent acetate should attack preferentially with inversion, the D-configuration now can be assigned without hesitation t o (+)-I, [-)-11, (+)-I11 and (+)-IV.3.4 (1) (a) R . Huisgen and H . Nakaten, An?:., 686, 84 (1954); R. Huisgen a n d Ch. Riichardt. ibid.. 601, 21 (1956); (b) E . H. White, T H I S J O U R N A L . 76, 4497 (1954); 77. MKl8, 6011. 6014 (1955); E. H. White and C. 4.Aufdermarsh, i b i d . . 80, 2597 (1958). (2) C . J. Collins, W. A . Bonner and C. T. Lester, ibid., 81, 466 (1959). (3) (+)-1,2.2-Triphenylethylacetate (111) has been converted t o (4-)-1.1,2-triphenylethylene glycol b y treatment with N-bromosuc-
(1951) I. (4) D-(+)-I11 yields D-(+)-IV upon treatment with lithium aluminum hydride.2 ( 5 ) H.France, I . M. Heilbron and D. H. Hey, J. Chcnz. Soc.. 369 (1940). (6) A detailed study of the stereochemistry and radiochemistry d t h e thermal decomposition of D- and L-I1 will be reported a t a later date. Since chain-labeling experiments similar t o those previously' reported indicate phenyl migration during the decomposition d 11, the rather considerable amount of labeled acetoxyl associated with D(-1.111 may be attributed t o inversion aribing through phenyl migration through a cis-transition state in the ionic intermediates involved. (7) Taken from the Ph.D. dissertation of Dr. Joan B Christie, University of Florida, Gainesville. August, 1959 Predoctoral Fellow of the Oak Ridge Institute of Nuclear Studies. (8) This paper is based upon work performed a t Oak Ridge National Laboratory, which is operated b y Union Carbide Corporation for the Atomic Energy Commission.
CHEMISTRY DIVISION OAK RIDGENATIONAL LABORATORY OAKRIDGE,TENNESSEE CLAIRJ . C O L L ~ S DEPART>IEST OF CHEMISTRY ~JSIVERSITY OF FLORIDA JOAN B. CHRISTIE RECEIVED JANUARY 18, 1900 THE ENERGY DIFFERENCE BETWEEN THE BOAT AND CHAIR FORMS OF CYCLOHEXANE Sir :
It is well accepted that the chair is more stable than the boat forin of cyclohexane; however, attempts to estimate the magnitude of this energy difference have yielded values ranging from as little as 1.31' t o as much as 10.6' kcal./mole. \Ye re(1) T h e lower value of the range calculated by D. H . R. Barton,
J . Chsm. Soc., 340 71945). (2) The higher value uf a range calculated by the Turner semiempirical method as described by W. G. Dauben and K . S Pitzer in h l . S. Newman's "Steric Effects in Organic Chemistry." John \','iley l % % ,p 15. and Sons, I n c . . New York, S . T..
