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Computational Investigation of the Competition between the Concerted Diels¨CAlder Reaction and Formation of Diradicals in Reactions of Acrylonitrile with Nonpolar Dienes The energetics of the Diels¨CAlder cycloaddition reactions of several 1,3-dienes with acrylonitrile, and the energetics of formation of diradicals, were investigated with density functional theory (B3LYP and M06¨C2X) and compared to experimental data (Hall et al., J. Org. Chem.1993, 58, 7049¨C7058). For the reaction of 2,3-dimethyl-1,3-butadiene with acrylonitrile, the concerted reaction is favored over the diradical pathway by 2.5 kcal/mol using B3LYP/6-31G(d); experimentally, this reaction gives both cycloadduct and copolymer. The concerted cycloaddition of cyclopentadiene with acrylonitrile is preferred computationally over the stepwise pathway by 5.9 kcal/mol; experimentally, only the Diels¨CAlder adduct is formed. For the reactions of (E)-1,3-pentadiene and acrylonitrile, both cycloaddition and copolymerization were observed experimentally; these trends were mimicked by the computational results, which showed only a 1.2 kcal/mol preference for the concerted pathway. For the reactions of (Z)-1,3-pentadiene and acrylonitrile, the stepwise pathway is preferred by 3.9 kcal/mol, in agreement with previous experimental findings that only polymerization occurs. M06¨C2X is known to give more accurate activation and reaction energetics (Pieniazek, et al., Angew. Chem. Int.2008, 47, 7746¨C7749), but the energies of diradicals are too high. |
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zhtear99
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4Â¥2013-06-25 09:37:26
yangchaotom
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Natalie C. James †, Joann M. Um †, Anne B. Padias ‡, H. K. Hall , Jr.‡, and K. N. Houk *† † Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States ‡ Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States J. Org. Chem., Article ASAP DOI: 10.1021/jo400900x Publication Date (Web): June 11, 2013 Copyright © 2013 American Chemical Society *E-mail: houk@chem.ucla.edu. ËÔÚѧУ°ïÎÒÏÂÔØÏÂÈ«Îİɣ¬ÔÚ¼ÒûÊý¾Ý¿â°¡ |
2Â¥2013-06-24 22:33:53
zhtear99
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3Â¥2013-06-25 09:36:00
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5Â¥2013-07-04 10:44:15













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