24273-80-1Relevant articles and documents
"Snap-shooting" the interface of AOT reverse micelles: Use of chemical trapping
Srilakshmi, Gollapudi Venkata,Chaudhuri, Arabinda
, p. 2847 - 2853 (2000)
The first use of the phenyl cation trapping technique in "snap-shooting" the local molar concentrations of water and sulfosuccinate head-groups in the interfacial region of AOT-2,2,4-trimethylpentane-water reverse micelles has been accomplished. Our results demonstrate that the interfacial concentrations of the sulfosuccinate head-groups in AOT (0.1M)-2,2,4-trimethylpentane-water reverse micelles are remarkably high (2.75-2.34M) across the W0 (the molar ratio of water to surfactant) range 12 to 44. However, the interfacial concentrations of water in AOT-2,2,4-trimethylpentane-water reverse micelles across the same range of solution compositions are significantly lower (27.9-32.0M) than the molar concentration of bulk water (55.5M). The present results provide new insight on the microenvironments of interfacially located enzymes such as lipases entrapped in AOT-2,2,4-trimethylpentane-water reverse micelles, the most extensively exploited reverse-micellar system in micellar biotechnology.
Molecular Dynamics Simulations of the Initial-State Predict Product Distributions of Dediazoniation of Aryldiazonium in Binary Solvents
Cruz, Gustavo N.,Lima, Filipe S.,Dias, Luís G.,El Seoud, Omar A.,Horinek, Dominik,Chaimovich, Hernan,Cuccovia, Iolanda M.
, p. 8637 - 8642 (2015)
The dediazoniation of aryldiazonium salts in mixed solvents proceeds by a borderline SN1 and SN2 pathway, and product distribution should be proportional to the composition of the solvation shell of the carbon attached to the -N2 group (ipso carbon). The rates of dediazoniation of 2,4,6-trimethylbenzenediazonium in water, methanol, ethanol, propanol, and acetonitrile were similar, but measured product distributions were noticeably dependent on the nature of the water/cosolvent mixture. Here we demonstrated that solvent distribution in the first solvation shell of the ipso carbon, calculated from classical molecular dynamics simulations, is equal to the measured product distribution. Furthermore, we showed that regardless of the charge distribution of the initial state, i.e., whether the positive charge is smeared over the molecule or localized on phenyl moiety, the solvent distribution around the reaction center is nearly the same.
Revisiting the reactions of nucleophiles with arenediazonium ions: Dediazoniation of arenediazonium salts in aqueous and micellar solutions containing alkyl sulfates and alkanesulfonates and an ab initio analysis of the reaction pathway
Cuccovia, Iolanda M.,Da Silva, Marcia A.,Ferraz, Helena M.C.,Pliego Jr., Josefredo R.,Riveros, Jose M.,Chaimovich, Hernan
, p. 1896 - 1907 (2007/10/03)
Dediazoniation of 2,4,6-trimethylbenzenediazonium tetrafluoroborate, 1-ArN2BF4 (for the z-Ar compounds described in this paper, z refers to the length of the carbon chain of the substituent at C4 of the benzene ring), in aqueous solutions containing sodium methyl sulfate, NaMeSO4, or sodium methanesulfonate, NaMeSO3, yields 2,4,6-trimethylphenol, 1-ArOH, 2,4,6-trimethylphenyl methyl sulfate, 1-ArOSO3Me and 2,4,6-trimethyl-phenyl methanesulfonate, 1-ArO3SMe, respectively. The relative yields of 1-ArO3SMe or 1-ArOSO3Me and 1-ArOH depend on the NaMeSO4 or NaMeSO3 concentrations. 4-n-Hexadecyl-2,6-dimethylbenzenediazonium tetrafluoroborate, 16-ArN2BF4, was used to determine the local head group concentration in sodium dodecyl sulfate and sodium dodecanesulfonate micelles by chemical trapping comparing the relative product yields with those obtained in water using the short chain analogs. Ab initio calculations of the spontaneous dediazoniation of phenyldiazonium ion in the gas phase, as well as in aqueous solution with, or without, added MeSO3-, yield potential energy surfaces for the reaction. For this model the calculated and experimental values of the spontaneous dediazoniation rate constants in aqueous solution, as well as the product composition, were similar to those obtained with 1-ArN2+. These results suggest that in aqueous solution nucleophiles can only compete with water if a diazonium ion·nucleophile complex is formed prior to N2 loss. Calculations show that the addition of nucleophiles to the arenediazonium ion occurs without a saddle point in the potential energy surface, suggesting that the free phenyl cation is not an obligatory intermediate in aqueous solutions.
