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C−H Activation by Direct Borane–Hydrocarbon Dehydrogenation: Kinetic and Thermodynamic Aspects
Author(s) -
Goldfuss Bernd,
Knochel Paul,
Bromm Lars O.,
Knapp Kolja
Publication year - 2000
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/1521-3773(20001117)39:22<4136::aid-anie4136>3.0.co;2-f
Subject(s) - dehydrogenation , chemistry , benzene , exothermic reaction , borane , transition state , reactivity (psychology) , photochemistry , activation energy , hydrocarbon , kinetic energy , computational chemistry , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics
Direct, uncatalyzed B−C bond formations by dehydrogenation reactions between borane and methane (the calculated transition structure is shown) as well as between borane and monosubstituted benzene derivatives (attack at the para position) proceed via four‐center transition structures with relatively small electronic, enthalpic, and free energies of activation (≤30 kcal mol −1 ). Donor substituents on benzene derivatives decrease the activation energies even further by stabilizing the forming B−C bonds in the transition structures and render the reactions more exothermic. The reactivity pattern of these direct dehydrogenations depends on the electronic character of the substituents and hence offers possibilities for directing selective C−H functionalizations.