Singlet carbene stability: linear free energy analysis of substituent effects

Linear free energy correlation analysis on the electronic effects of Rh(II) carbene O-H insertion.

The relative rate constants for the Rh(II)-catalyzed insertion of diazoacetone into the O-H bond have been measured through intermolecular competitions. The kinetic data were subjected to Hammett correlation analysis, and mechanistic implication of the results with respect to a stepwise vs a concerted O-H insertion pathway is discussed.

Catalytic and Biocatalytic Iron Porphyrin Carbene Formation: Effects of Binding Mode, Carbene Substituent, Porphyrin Substituent, and Protein Axial Ligand

Iron porphyrin carbenes (IPCs) are important intermediates in various chemical reactions catalyzed by iron porphyrins and engineered heme proteins, as well as in the metabolism of various xenobiotics by cytochrome P450. However, there are no prior theoretical reports to help understand their formation mechanisms and identify key information governing the binding mode, formation feasibility, and...

Electronic effects on singlet-triplet energy splittings in aryl-cyclopentadienylidenes

Energy gaps, AXsar (X=E, H and G) (AX.,.,-=lia,„,,,InrX“dpka,) between single (s) and triplet (I) states werecalculated at B3LTP/6-3 I 1.HO" level of theory. Our results showed that electron donating substituents(G = -NHz, -OH. -CH), -F, -Cl and -Br) at phenyl group cause to increase and electron withdrawingsubstiluents (G -CF2. and -NO:) lead to decrease the singlet-triplet energy gaps of Ar -...

A new class of singlet carbene ligands.

Reaction pathways and free energy profiles for spontaneous hydrolysis of urea and tetramethylurea: unexpected substituent effects.

It has been difficult to directly measure the spontaneous hydrolysis rate of urea and, thus, 1,1,3,3-tetramethylurea (Me4U) was used as a model to determine the "experimental" rate constant for urea hydrolysis. The use of Me4U was based on an assumption that the rate of urea hydrolysis should be 2.8 times that of Me4U hydrolysis because the rate of acetamide hydrolysis is 2.8 times that of N,N-...