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Experimental determination of the relative rates of rotation, cleavage, closure, and 1,5-hydrogen shift for 3-methyl-1,4-pentanediyl. Evidence for 1,4 biradicals as common intermediates from different precursors, 3,4-(and 3,6-)dimethyl-3,4,5,6-tetrahydropyridazines and 1,2-dimethylcyclobutanes

Dervan, Peter B. and Uyehara, Tadao and Santilli, Donald S. (1979) Experimental determination of the relative rates of rotation, cleavage, closure, and 1,5-hydrogen shift for 3-methyl-1,4-pentanediyl. Evidence for 1,4 biradicals as common intermediates from different precursors, 3,4-(and 3,6-)dimethyl-3,4,5,6-tetrahydropyridazines and 1,2-dimethylcyclobutanes. Journal of the American Chemical Society, 101 (8). pp. 2069-2075. ISSN 0002-7863. http://resolver.caltech.edu/CaltechAUTHORS:20160516-093833884

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Abstract

Thermal decomposition of cis- and trans-3,6-dimethyl-3,4,5,6-tetrahydropyridazine (11 and 12, respectively) affords propene, els- and trans-1,2-dimethylcyclobutanes, and 1-hexene. The stereochemistry of the products is consistent with a 1,4-biradical intermediate(s) 2,5-hexanediyl, which has the properties k(rotation) ~ k(cleavage) ~ k(closure). At 439°C the retention/inversion (r/I) ratios for the 1,2-dimethylcyclobutane products are 1.7 and 1.7 from 11 and 12, respectively. At 306°C, these ratios are 1.9 and 2.2, respectively. The results indicate that when the thermal reactions of cyclic azo compounds and cyclobutanes of similar substitution are compared at similar temperatures, the stereospecificities are similar. We conclude that stereoretention is dependent on both substitution and temperature, i.e., stereospecificity increases as substitution at the radical center increases and as the temperature is lowered. The thermal decomposition of cis- and trans-3,4-dimethyl-3,4,5, tetrahydropyridazine (19 and 20, respectively) allows a dissection of direct vs. 1,4-biradical pathways in six-membered cyclic azo decompositions, e.g., 36% direct/64% 1,4 biradical from cis-19 and 32% direct/68% 1,4 biradical from trans-20. The ...tive rates of rotation, cleavage, and closure for azo-generated 1,4 biradicals, 3-methyl-1,4-pentanediyl (ST and SC), w... determined. For 8T, k (cleavage)/ k( closure) = 1.6 and k(closure) / k(rotation) = 1.9. For SC, k (cleavage)/ k( closure) = 1.8 and k( closure)/ k(rotation) = 0. 7. These relative rates of rotation, cleavage, and closure generate similar trans-/cis-2-butene ratios as found in the pyrolyses of cis- and trans-1,2-dimethylcyclobutanes at the same temperature and phase. We conclude they pass the stereochemical test for identity, indicating evidence for common 1,4-biradical intermediates from two different precursors (1,2-diazenes and cyclobutanes). Finally, the data are compared with the recent literature values reported for the dimerization of ethylene and 2-butenes.


Item Type:Article
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http://dx.doi.org/10.1021/ja00502a022DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja00502a022PublisherArticle
Additional Information:© 1979 American Chemical Society. Received August 30, 1978. Publication Date: April 1979. Acknowledgment is made to E. I. DuPont de Nemours and Co. for a DuPont Young Faculty Grant and to the National Science Foundation (CHE75-06776) for their generous support.
Funders:
Funding AgencyGrant Number
E. I. DuPont de Nemours and Company, Inc.UNSPECIFIED
NSFCHE75-06776
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Caltech Crellin Laboratory of Chemistry5860
Record Number:CaltechAUTHORS:20160516-093833884
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160516-093833884
Official Citation:Experimental determination of the relative rates of rotation, cleavage, closure, and 1,5-hydrogen shift for 3-methyl-1,4-pentanediyl. Evidence for 1,4 biradicals as common intermediates from different precursors, 3,4-(and 3,6-)dimethyl-3,4,5,6-tetrahydropyridazines and 1,2-dimethylcyclobutanes Peter B. Dervan, Tadao Uyehara, and Donald S. Santilli Journal of the American Chemical Society 1979 101 (8), 2069-2075 DOI: 10.1021/ja00502a022
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67108
Collection:CaltechAUTHORS
Deposited By: Victoria Brennan
Deposited On:16 May 2016 21:52
Last Modified:16 May 2016 21:52

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