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our laboratories to elucidate the exact origin of the observed isotope effects and the reason for their variation with nature and concentration of the peroxide.
(higher boiling). Above a critical lower temperature, the composition of the pyrolyzate appears to be independent of the temperature and extent of pyrolysis. Thus, pyrolysis of Zheptyl acetate at A c l c n o w M : This work is a contribution from 450" and a flow rate of 1 g. per minute gave only the Radiation Project of the University of Notre 35% of heptenes identical in composition with Dame, supported in part under AEC Contract AT- the product described above. Pyrolysis of Pheptyl acetate, which can lead to (11-1)-38. We are grateful to Professor D. F. DeTar only one structural isomer without bond rearrangefor a discussion of unpublished work from his labon pyrolysis 'at 485" and flow rate 0.8 g. ment, oratory and helpful suggestions arising therefrom. per minute gave 86% of 3-heptene (b.p. 93-95.5", DEPARTMENT OF CHEMISTRY ER.XEST L. ELIEL ng 1.4012; liL6 b.p. 95.8-96.1", n g 1.4090). UNIVERSITY OF NOTRE DAME Z~LTAN WELVAET~~This material was homogeneous to the Ucon NOTRE Dam, IND. SAMUEL H. WILEN chromatographiccolumn except for a small shoulder (11) On leave of absence from C.N.R.S., P&, France, on the high-retention side of the single peak; this on a Fulbright Tmvel Grant. shoulder is interpreted ~ t being s due to the presence of a small amount of &-3-heptene, the major Received September 15, 1958 component being the trumisomer. Pyrolysis of 3-heptyl acetate a t 485" and flow rate 0.6 g. per minute gave a mixture of heptenes (b.p. 91-97", Pyrolysis of Esters. I. Nonselectivity in ng 1.4022) in 84% yield. Gas chromatographic the Direction of Elimination by Pyrolysis malysis over the Ucon column showed 53.5% of 3-heptene) 34.7% of tra+%heptene, and 11.8% Sir: of cis-2-heptene. The 3-heptene peak showed a We wish to report that published' generalizations shoulder on the high-retention side indicating the regarding the direction of elimination on pyrolysis presence of a small amount of the cis-isomer. We have also reinvestigated a specific example of esters are in grave error. We now find that pyrolysis of secondary acetates gives in appreciable reported by Bailey and King.' Pyrolysis of methylamounts both possible alkenes as well as cts and isobutylcarbinyl acetate a t 485" and flow rate 0.75 trans isomers when such isomerism is possible. g. per minute gave in 72.2% yield an ole& mixture Pyrolysis of l-heptyl acetate (b.p. 186-187") which on chromatographic analysis over the Ucon 1.41653) column showed two components in the amounts of n g 1.4120; lit.* b.p. 192.5", nge((ye~.l a t 540" and a flow rate of 0.6 g. per minute gave 44.5% (low retention) and 55.4% (high retention). pure l-heptene (b.p. 90-93", ng 1.3962; lit.$ b.p. We assume that the low retention isomer is the 93.5", ng 1.3998) in 56% yield. Homogeneity of lower boiling7 +methyl-l-pentene, while the high this material was .established by gas chromatogra- retention isomer is the higher boiling7 4-methyl-2phic analysis using the Wilkins Aerograph equipped pentene. In view of these results, we must regretfully conwith a &foot silicone column and with a 10-foot clude that the generalizations and the experimental Ucon Polar column. Pyrolysis of 2-heptyl acetate observations of Bailey and associates1are in error. (b.p. 171-173",ng 1.4050; lit.* b.p. 71" at 17 mm., We attribute this experimentalerror to failure of the n g 1.4089) a t 485" and a flow rate of 0.67 g. per earlier investigators to utilize precise fractional disminute gave a mixture of isomeric heptenes (b.p. tillation, thus necessitating the assignment of struc92-98", n g 1.3994; lit.: trans-%heptene, b.p. ture and estimation of homogeneity on infrared 97.5-99", n g 1.4056, cis-2-heptene, b.p. 98.5- analysis alone. Infrared analysis is not an infal99.5", ng 1.4052) in 84% yield. Gas chromato- lible criterion when mixtures are being compared. graphic analysis over the 10-foot Ucon Polar We do not wish to generalize our observations at column showed 53.9% l-heptene, 29.3% trans-2- this time. Extensive further investigations are heptene (low boiling), and 16.8% &-2-heptene planned. OF ~ I L I S T S Y E. EaBG ROYUS (1) W. J. Bsiley and C. King, J . Am. clmn. Soc., 77, DEPABTMIENT EMORY U N I V E B S ~ ~ 75 (1955); W. J. Bailey, J. J. Hewlitt, and C. King, J. Am. ATLANTA 22, GA. chcm.sue, 77,357 (1955). (2) R.Bilterys and J. Gieseleire, BuU. aoc. d i m . Belg., 44, Received September 29,1958 576 (1935). (3) M.L. Sherrill, E;. E. Mayer, and G. F. Walter, J. Am. chcm.Soc., 56,927 (1934). (6) F.J. Soday and C.E.Boord, J . Am. C h . Soc., 55, (4) R H. Pickard and J. Kenyon, J. clrmr. Soc., 105,852 3295,3300 (1933).
(1914). (5) B.Gredy, Bull. aoc. d i m . Be&. ( 5 )2,1031 (1935).
(7) C.G.SchmittandC.E.Boord,J.Am.Chcm.Soc.,S4, 754,760 (1932).
