Relating alkaline stability to the structure of quaternary phosphonium cations

A semi-empirical formula based on the Taft equation is established to directly estimate alkaline stability of quaternary phosphonium (QP) cations from the 31P NMR chemical shift δ and the steric substituent constant Es.

Substituent effects on selectivity of coupled oxidation of iron tetraphenylporphyrins

Coupled oxidation of iron tetraphenylporphyrins bearing either a OMe , Me , F , Cl , COOMe , CF 3 or CN group in the para-position of the phenyl groups gave tetraarylbiladien-ab-1-one and triarylbilindione. The ratios of the yields of the former to those of the latter were linearly correlated with the Hammett substituent constants σp+, with a positive slope (Δρ = 0.64). The Hammett plot of the oxidation rate vs. the substituent constant σp also showed a positive slope (ρ = 0.30). These substituent effects suggest that a nucleophilic step is included in the formation of bilindione. Coupled oxidation of an A3B type tetraarylporphyrin having an electron withdrawing nitro group in one of the phenyl groups indicated that the oxidation leading to biladienone occurred rather statistically in any of the meso-positions, while the oxidation leading to bilindione occurred preferentially in the meso-position bearing the 4-nitrophenyl group.

Predicting the cation–π binding of substituted benzenes: energy decomposition calculations and the development of a cation–π substituent constant

This work proposes a new substituent constant,Π+, to describe cation–π binding using computational methods at the MP2(full)/6-311++G** level of theory with Symmetry Adapted Perturbation Theory (SAPT) calculations on selected cation–π complexes.

Electrochemical studies of certain nitro substituted pyrazolin-5-ones

The polarographic behavior of 1-(Toluenyl sulfonyl)-3-amino-4-(2'-nitro aryl hydrazono)-2-pyrazolin-5-one and 1-(Toluenyl sulfonyl)-3-amino-4-(4'-nitro aryl hydrazono)-2-pyrazolin-5-one is investigated in the acidic as well as in basic media. The compounds gave two well defined, diffusion controlled, irreversible waves in Britton-Robinson buffers of pH range 1.0-7.0. In alkaline medium three well defined, diffusion controlled and irreversible waves were obtained. Effect of various solvents, cations and surfactants on the reduction is presented. The effect of substituent and its correlation with the Hammett substituent constant (δ) is detailed. Based on the results, a detailed reduction mechanism in acidic as well as basic media is proposed.