Jan. 20, 1957
COMMUNICATIONS TO THE EDITOR
505
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1.00 0.03 per deuterium (determined by direct rate comparison rather than by competition experiment). Under mercuration conditions, toluene-a-t did exchange tritium slowly with the solFACULTY OF TECHNOLOGY vent, but the exchange reached less than 5% UNIVERSITY OF MANCHESTER, ENGLAND E. SPINNER completion during the time of the mercuration NATIONAL RESEARCH COUNCIL OF CANADA, OTTAWA, ONTARIO kinetics. RECEIVED NOVEMBER 20, 1956 In bromination of toluene-a-t b y Br2 (0.05 AT reactants in 85% acetic acid-l5% water solution) a t 25' the molar activity of toluene recovered after RELATIVE REACTIVITIES OF TOLUENE, TOLUENE- 81% reaction showed a 7.7 =t 1.4% increase, a,a,a-& AND TOLUENE-a-t IN ELECTROPHILIC corresponding to a n isotope effect of 1.046 =t NITRATION, MERCURATION AND BROMINATION' 0.009 for k H / k T or 1.03 f 0.01 for k H / k D per deuterium atom. Bromotoluenes from complete Sir: bromination had the same molar activity as the We have found that secondary isotope effects on the rate of nuclear aromatic nitration, mercura- toluene within experimental error (=t 3%). tion and bromination due t o isotopic substitution DEPARTMENT OF CHEMISTRY AND C. GARDNER SWAIX FOR XCCLEAR SCIEXCETERENCE E. C. KXEE for hydrogen in the methyl group are 3% per LABORATORY IXSTITUTE OF TECHNOLOGY deuterium atom or less. The larger (4-3070 MASSACHUSETTS A . JERRYKRESGE MASSACHUSETTS per deuterium) secondary isotope effects previously CAMBRIDGE, observed in solvolysis have been interpreted in RECEIVED OCTOBER1, 1956 terms of hyperconjugation in the transition state. Therefore either hyperconjugation is relatively less important in these aromatic substitutions than in s~J~-~-NORBORNENYL TOLUENESULFONATE' the solvolyses (including p-CH3*CeH&HClCH3 in acetic acid a t 50') or the reported p-methyl isotope Sir: effects in solvolysis are not measuring hyperconjugation. I n view of the extreme importance As reported recently,2 anti-7-norbornenyl pof other kinds of resonance in aromatic substitution toluenesulfonate (IV) is more reactive than the (e.g., relative rates of about lo'*:lo9:1 for bromina- related 7-norbornyl derivative (VI) in acetolysis tion of aniline, anisole and benzene8) i t is un- by a factor of lo", the anchimerically assisted expected that hyperconjugation should be so ionization leading to cation (VII). We now report minor. Therefore we favor the latter interpreta- the preparation of the previously unavailable isotion. meric syn-7-norbornenol (111) and the novel Summarizing our experimental results : Toluene- solvolytic behavior of its toluenesulfonate (V). a,a,a-da (2.7 D) and toluene-a-t were prepared by From opening of bicycloheptene oxide (I) with reduction of a ,a ,a-trichlorotoluene with zinc and hydrogen bromide, there is obtained predominantly acetic acid-d or -t.4 The molar activity of toluene- the Wagner-Meerwein rearranged bromohydrin a-t recovered after 92y0 reaction with nitronium (II), m.p. 75-76'. By the action of potassium ion (0.5 M toluene plus 10 iM nitric acid containing t-butoxide in benzene on the toluenesulfonate of 20% water by volume) a t 25' was 0.86 =t 0.77% the bromohydrin (11), there is obtained syn-7higher than that of the starting material (scintilla- norbornenyl toluenesulfonate (V), m.p. 67-68', in tion counting) corresponding to an isotope effect ca. 80% yield. Hydrogenation of this material of 1.003 f 0.003 for k H / k T or 1.002 f 0.002 for leads to the known 7-norbornyl derivative (VI). k H / k D per deuterium atom. There was no exAnalogous treatment of the tetrahydropyranyl change of methyl hydrogens under these nitration derivative of the bromohydrin I1 with potassium conditions, since the nitrotoluenes produced had t-butoxide and hydrolysis led to syn-7-norbornenol the same molar activity as the starting material (III), m.p. of phenylurethan 125-12G0, m.p. of within 2.8 f 3.5Y0 (ionization chamber counting). p-toluenesulfonate 67-68'. Mercuration of toluene-a,cu,a-d3by Hg++ (0.2 AI First order rate constants of acetolysis of the toluene plus 0.05 M mercuric acetate in acetic acid syn-toluenesulfonate (V) are (1.17 =t 0.02) X l o w 6 solution containing 0.25 M water and 0.50 M set.-' a t 100.0' and (1.28 f 0.01) x set.-' perchloric acid) a t 25' gave an isotope effect of a t 122.2', leading to an extrapolated value of 2.6 X lo-" set.-' a t 25'. While the syn-material (1) The bromination work was supported by the Office of Na\,al Research under Contract No. N5ori-07838 (cf. T. E. C . K . , P h . D . (V) is slower than its anti-isomer (IV) by a factor of thesis, M . I. T., Sept., 1956, for complete experimental data) and sublo', i t is nevertheless anchimerically accelerated, sequent mercuration and nitration work (by A. J . K.) by the Atomic since i t is more reactive than the 7-norbornyl Energy Commission under Contract N o . AT(30-1)-905. Reproducester (VI) by a factor of lo4. The source of the tion is permitted for any purpore of the United States Government. anchimeric assistance is clear from the nature of the 0 E . S . Lewis and C. E . Boozer, THISJOURNAL, 74, 6306 (1952); 76, 791, 794 (1954); V. J. Shiner, Jr.. i b i d . . 76, 2925 (1953); 76, 1603 solvolysis product from (V). this represents the greater part of the stabilization conventionally attributed to *-electron delocalization.
(1954); 78, 2653 (1956); E . S. Lewis and G. M. Coppinger, ibid., 76, 4495 (1954); E. S. Lewis and R. R. Johnson, Abstracts of Papers presented at 130th Meeting of the American Chemical SOC., Atlantic City, New Jersey, Sept. 16 t o 21, 1956, p. 2 0 - 0 ; A. Streitweiser, R. H. Jagow and S. Suzuki, THISJOURNAL, 77,6713 (1955). (3) P . W. Robertson, P. B . D. de !a Mare and B. E. Swedlund, J. Chcm. S o c . , 782 (1953). (4) R . Renaud and L. C. Leitch, Can. J . Chcm., 3 4 , 9 8 (1956).
( 1 ) (a) Research sponsored by the Office of Ordnance Research, U. S. Army; (b) supported in part by the Petroleum Research Fund of the American Chemical Society. (2) (a) S Winstein, M . Shatavsky, C. Norton and R. B. Woodward, THISJOURNAL, 77, 4183 (lQ.55): (b) S. Winstein and M . Shatavsky, ibid., 78, 592 (1956); (c) C. J. Norton, Thesis, Harvard University. 1955.
