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diazepinone product must be 3.16 The nmr spectrum of 9, as compared to that of 4, can be accounted for by anisotropic shielding of the alkenyl protons by the bay proton on the naphthalene nucleus.Careful examination of the reaction mixture and subsequent mother liquors from crystallizations failed to reveal the presence of any 2. Interruption of the boiling xylene reaction in the hope of isolating 2 or other intermediates was unsuccessful. Condensation reactions carried out at lower temperatures also failed to give 2; a similar product distribution of 3 and 4 was obtained in boiling toluene as solvent and in boiling benzene essentially no reaction occurred. We believe that the formation of 3 and 4 in this reaction can best be explained by considering that both diazepinone products 2 and 3 were initially formed. 3, which was found to be resistant to thermal rearrangement, was not further affected by the reaction conditions. However, 2, because of an apparently very low energy barrier for ring contraction, must have been converted immediately and quantitatively into 4. Attempts to prepare 2 by an independent route in order to study its rearrangement unfortunately failed to give the desired product.Catalytic reduction of 3 in acetic acid4 afforded the tetrahydrodiazepinone 10, mp 209°. This material was similar to but not identical with the tetrahydrodiazepinone, mp 229-230°, prepared by fusion of 1,2-diaminonaphthalene with crotonic acid, according to the procedure of Ried and Hohne.4 The crotonic acid product is, therefore, correctly identified as 11, and not 10 as previously suggested.4Experimental Section16 1,5-Dihydro-2-methyl-4Ji-naphth [1,2-6] [1,4] diazepin-4-one (3) .-Prepared according to the procedure of Ried and Hohne,4 this material was previously described as 2. It formed white crystals from xylene: mp 246°; nmr (C5D5N) 2.43 (3 , s), 3.28 (2 , s), and 7.42-7.70 ppm (6 , multiple aromatic peaks); uv Xlhr' 243 nm (<= 55,700), 294 (7100), 308 (6900), 323 (4500), and 337 (4800). The presence of 2 in the reaction mixture could not be observed by spectral or tic studies.

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The results of this study demonstrate the existence of significant intramolecular differences in chlorinated organic compounds. Many other chlorinated semi-volatile and volatile organic contaminants are synthesized from multiple sources of chlorine, and we recommend that similar studies be performed on many such molecules in order to attain a clear understanding of their intramolecular chlorine isotopic differences. The existence of a measurable KIE for the dehydrochlorination of DDT to DDE shows the potential strength of using isotopic measurements to investigate the biogeochemistry of these important compounds. For example, the isotopically depleted aqueous chloride produced by dehydrochlorination of DDT to DDE may be a useful tracer of these reactions in freshwater environments.