March 20, 1962
COMMUNICATIONS TO THE EDITOR
with P-decalol in sulfuric acid to yield III.8 The factors responsible for the sole formation of the trans isomer in this reaction may be similar to those operating in the carbonylation of IV, where trans decalin-9-carboxylic acid is the kinetically favored product. This demonstration of the existence of an alternate mechanism for the Beckmann rearrangement when stable carbonium ions may be produced in strong acid media raises the possibility that some reported rearrangementsg carried out under these conditions are actually of the fragmentation-recombination type ; i t further serves as a warning to avoid these conditions in experiments in which retention of configuration is desired.
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ene were identified by gas chromatography). Generally, aliphatic compounds reacted in low conversion to give a large number of products, whereas their aromatic analogs formed a smaller number of products in higher yields. One representative series of results obtained in this reaction (the transformation of toluene) is shown in Table I. The virtual absence ( dsa (cf. ref. 3); ( b ) for a number of tate, Jaa,re acetylated pyranoses, 61, 5.66-6.11 ppm., 61a 5.37-5.75 ppm. (cf. ref. 3): (c) for hydrogens r m adjacent carbons, J,,, 5-8 cps., J.,e or J r , e = 2-3.5 cps. (cf. ref. 5 ) .
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(3) J. N. Shoolery and M. T. Rogers [ibid., 80, 5121 (1958)j give other examples showing that the equatorial proton absorbs a t a larger 6 value than its axial counterpart. (4) (a) This statement was based on calculations first treating three hydrogens, HI.. HI*. Has ( m as), a s an ABX system [J. A. Pople, W. G. Schneider and H. J. Bernstein. "High Resolution Nuclear Magnetic Resonance," McGraw-Hill Book Co., New York, N. Y., 1959, p. 1321, then splitting each of the resulting lines by the fourth ss). (b) The following constants (in cps.) were hydrogen Ha. 11.0, used t o derive the theoretical patterns shown in Fig. 1A: J4a.a. J4..& 11.0,Jte.sa = 2.1 (or 5.0).J4e.3a 5.0 (or 2.1). J4.,ra 12.5,84e 64* 43.0; and in Fig. 1C: J h s a 11.4,J ~ e , s s= 2.3, J S S=,, ~6.5. (5) J. N.Shoolery P'NMR and E P R Spectroscopy" by Varian staff, Pergamon Press, New York, N. Y.,1960, p. 1141 tabulates spln coupling constants for cyclohexane systems: Ja,a= 6-14 cps.. J B , ~ or JeSr = 0-6 cps.
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