651-07-0Relevant articles and documents
Sulfonic acid functionalized hyperbranched poly(ether sulfone) as a solid acid catalyst
Nabae, Yuta,Liang, Jie,Huang, Xuhui,Hayakawa, Teruaki,Kakimoto, Masa-Aki
, p. 3596 - 3602 (2014/07/08)
Sulfonic acid functionalized hyperbranched poly(ether sulfone) (SHBPES) was studied as a novel type of solid acid catalyst. Various molecular weights of SHBPESs were tested for the esterification reaction between acetic acid and 1-butanol. The SO3H terminal groups of the SHBPESs work as catalytically active sites, but all tested SHBPESs are totally or partially soluble under the current reaction conditions. To overcome the solubility problem, SHBPES was grafted onto carbon black, and this material, SHBPES/CB, shows fairly good catalytic activity and promising recyclability. The turnover frequency of SHBPES decreased upon grafting it onto carbon black, but it was still much better than that of Amberlyst-15. SHBPES/CB was also tested for the Friedel-Crafts alkylation of anisole and its durability seems to be much better than that of Amberlyst-15 under the operating conditions at 130°C. This journal is the Partner Organisations 2014.
A facile approach for the preparation of cross-linked sulfonated polyimide membranes for fuel cell application
Fang, Jianhua,Zhai, Fengxia,Guo, Xiaoxia,Xu, Hongjie,Okamoto, Ken-Ichi
experimental part, p. 1102 - 1108 (2009/10/15)
A facile approach has been successfully developed for the preparation of a series of cross-linked sulfonated polyimide (SPI) membranes via the condensation reaction between the sulfonic acid groups and the activated hydrogen atoms of SPIs in the presence of phosphorous pentoxide: methanesulfonic acid in the ratio of 1: 10 by weight (PPMA, method 1) or phosphorous pentoxide only (method 2). The resulting sulfonyl linkages are very stable and the cross-linked SPI membranes showed greatly improved water stability in comparison with the uncross-linked ones while high proton conductivity was maintained. The Royal Society of Chemistry.
Enolate Structures Contributing to the Transition State for Nucleophilic Substitution on α-Substituted Carbonyl Compounds
Yousaf, T. I.,Lewis, E. S.
, p. 6137 - 6142 (2007/10/02)
The high SN2 reactivity of α-halocarbonyl compounds is explained by the lowering of the intrinsic barrier by a major contribution of enolate structure to the transition state.This theoretical conclusion is now shown experimentally.The evidence is as follows: (1) Change in structure of a leaving arenesulfonate ion does not change the rates of attack of benzenesulfonate ion by nearly as much as it changes the equilibrium constants.A charge on the transferring phenacyl group of -0.48 is deduced. (2) The ρ value (-3.9) for attack of substituted thiophenoxides on phenacyl bromide is much more negative than that for attack on methyl iodide (-1.8). (3) A related ρ value is found for reaction of 2,4,6-trimethylphenacyl bromide with thiophenoxides (-2.2), showing a lesser, but still large sensitivity to nucleophile structure where addition to the carbonyl is sterically forbidden.The enolate structure leaves the attacking or leaving nucleophiles with a single electron each instead of the unshared pairs.Thus, the enolate structure is emphesized if the leaving group and the nucleophile readily lose an electron.
