Unusual Reaction Constant for Hydride Transfer from a Carbanion to 9‐Arylxanthyliums

Abstract

The reaction constant (ρ) from the kinetics for hydride transfer from a carbanion (XH–) to 9‐arylxanthylium ions (9‐GPhXn+) in CH3CN was unusually negative. Thermodynamic analysis indicated that ρ for the simple hydride transfers (only involved with release and capture of a hydride anion) should be positive; this is in contrast to the kinetics results. Consequently, this reaction is not a simple hydride transfer. An “intermediate” was also found in the reaction system, the formation of which resulted in the unusual ρ.

Discovering and Evaluating the Reducing Abilities of Polar Alkanes and Related Family Members as Organic Reductants Using Thermodynamics

“…In fact, the hydride affinities of Y in solution, Δ H H – A (Y), were determined from the hydride transfer reaction enthalpy change of the corresponding carbanions YH – with strong hydride acceptors in the previous studies of Cao’s and Zhu’s groups . In 2014, the hydride transfer mechanism from β-substituted carbanions to a carbocation and 9-arylxanthyliums were investigated by our group. , …”

“…54 In 2014, the hydride transfer mechanism from βsubstituted carbanions to a carbocation and 9-arylxanthyliums were investigated by our group. 55,56 In total, all YH − (47.9−63.1 kcal/mol) are unexpectedly identified as novel strong hydride reductants, which greatly expands the database of organic hydride reductants for chemists to query and select suitable reductants for different unsaturated compounds in chemical reactions.…”

Thermodynamics of the elementary steps of organic hydride chemistry determined in acetonitrile and their applications

“…Many efforts have been made to screen the real hydride acceptor. Fortunately, 4-acetylamino-2,2,6,6-tetramethyl-piperidine-1-oxoammonium [TEMPO + (396), hydride affinity of −105.6 kcal] 108 was screened as an appropriate hydride acceptor to absorb hydride from KH − . Consequently, a surprising strategy was first discovered to accurately determine the hydride affinities of aldehydes and ketones.…”