Journal ArticleDOI
Model calculations of hydrogen isotope effects for non-linear transition states
TLDR
In this paper, it was shown that primary hydrogen isotope effects depend smoothly on transition-state geometry and yield consistently low values, kH/kD= 1−2, for sufficiently non-linear configurations.Abstract:
Calculations are reported showing that primary hydrogen isotope effects depend smoothly on transition-state geometry and yield consistently low values, kH/kD= 1–2, for sufficiently non-linear configurations. Specific calculations for 1,2-hydride shifts, borane hydrolyses, and E2C eliminations are compared with available measurements for these and for other hydrogen-transfer reactions proceeding through 3-, 4-, 5-, and 6-membered cyclic transition states. A unique temperature-independent kH/kD is noted. The low isotope effects are ascribed to the presence of a large isotopically sensitive vibration νR‡(e.g., 3500 cm.–1) in the transition state. The results are fairly insensitive to reasonable force-constant changes. The usefulness of kH/kD in defining the geometry of transition states for hydride transfer reactions is discussed.read more
Citations
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Journal ArticleDOI
Dioxygen Activation and Methane Hydroxylation by Soluble Methane Monooxygenase: A Tale of Two Irons and Three Proteins
Maarten Merkx,Daniel A. Kopp,Matthew H. Sazinsky,Jessica L. Blazyk,Jens Müller,Stephen J. Lippard +5 more
TL;DR: Different aspects of catalysis by the MMO proteins are examined, including the mechanisms of dioxygen activation at the diiron site and substrate hydroxylation by the activated oxygen species.
Journal ArticleDOI
Reevaluation of the Mechanism of the Baylis–Hillman Reaction: Implications for Asymmetric Catalysis
Journal ArticleDOI
Homogeneous Catalytic Dehydrocoupling/Dehydrogenation of Amine-Borane Adducts by Early Transition Metal, Group 4 Metallocene Complexes
Matthew E. Sloan,Anne Staubitz,Timothy J. Clark,Christopher A. Russell,Guy C. Lloyd-Jones,Ian Manners +5 more
TL;DR: The efficient catalytic dehydrocoupling of a range of amine-borane adducts by a series of group 4 metallocene type precatalysts has been demonstrated and the proposal of a two cycle, four step reaction mechanism is proposed.
Book ChapterDOI
Oxygen Activation and Transfer
TL;DR: The cytochrome P-450-catalyzed insertion of an oxygen into a substrate culminates a process that reduces molecular oxygen to a species equivalent, in terms of formal electron count and reactivity, to an oxygen atom.
Book ChapterDOI
Oxygen Activation and Reactivity
TL;DR: This chapter concentrates on the nature of the activated oxidizing species, the shunt pathways for its formation, and its reactions with organic substrates.