M. Nelsen, Jr., and V. A. Campanile for capillary glpc analyses, and Dr. D. 0. Geymer for dosimetry measurements. Also the author expresses appreciation for helpful discussions with F. F. Rust and Dr. C. D.Wagner.(9) Recent experiments using ionizing radiation as the source of radical initiation (L. H. Gale, unpublished results) demonstrate that lowering the reaction temperature for addition of HBr to neat 1-hexene to -13" yields a product with the composition: 97,Oz 1-bromo-, 2.46% 2-bromo-, and 0.50% 3-bromohexane. The low yield of 3-bromohexane indicates that the double-bond migration is practically negligible at -13" and that the bulk of the 2-bromohexane arises from ionic addition to 1-hexene. Also increasing the HBr concentration at 5" decreases the combined yield of 2-bromo-and 3-bromohexanes which is consistent with the behavior predicted by expression 10. Abstract:The unique loss of 64 mass units (sulfur dioxide) observed in the mass spectrum of tolbutamide,' the most energetically favored fragmentation, has been shown by deuterium labeling and high-resolution mass spectrometry to involve two rearrangement mechanisms. The contribution of each was assessed individually from the accurate mass measurements of the pertinent fragment ions. Some thermal decomposition of the sample was observed due to a high source temperature and/or high inlet system temperature.he mass spectrum of tolbutamide (I)' shows a loss

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Addition to Bicyclo [3.1.0]hexene-2 771 give 48 mg. (27%) of Ilia, m.p. 198°. The analytical sample, m.p. 202°( sharp), was obtained by recrystallization from ethyl acetate. The infrared spectrum (KBr) had bands at 2750, 1712 (aldehyde), 2237 (nitrile), and 1728, 1236 cm.-1 (acetate). The n.m.r. spectrum (CDC13) had doublets in the vinyl proton region at 5.97

added to suppress ionization. Sodium chloride was added to Registry No.-Me2N(CH2)2NH2, 108-00-9; Me2N-(CH2)3NH2, 109-55-7; Me2N(CH2)4NH2, 3529-10-0; Me2N(CH2)6NH2, 3209-46-9. Acknowledgment.-We wish to thank Kenneth W.Narducy for the computer calculation of the pK values reported here.

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