- Alkylation of ammonium salts catalyzed by imidazolium-based ionic liquid catalysts
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Quaternary ammonium salts were synthesized from ammonium salts and dialkyl carbonates over imidazolium ionic liquid catalysts. The reaction gave almost stoichiometric amounts of the quaternary ammonium salts for halides and nitrates. It was found that the electron-donating property of the alkyl moieties of ammonium cations, the electrophilic nature of the alkyl group of the carbonate, the acidity of the acid that the anion of the ammonium salt corresponds to, and the steric hindrance of the ammonium salts and the dialkyl carbonates are the key factors that influence the yields of quaternary ammonium salts. Strong electron-donating alkyl groups on the nitrogen atom of the ammonium salt, electron-withdrawing groups on the methylene carbon of dialkyl carbonate, and weaker steric hindrance of the starting ammonium salts and dialkyl carbonates favor the alkylation reaction of ammonium salts.
- Zheng, Zhuo Qun,Wang, Jie,Wu, Ting Hua,Zhou, Xiao Ping
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p. 1095 - 1101
(2008/03/27)
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- Recognition of quaternary ammonium salts with tetrapeptides containing α-aminoisobutyric acid as a conformational constraint
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Tetrapeptides Trp-Aib-Gly-Leu-NH-Ar (Aib:α-aminoisobutyric acid, 2-amino-2-methylpropanoic acid, Ar = phenyl or 3,5-dimethylphenyl) were synthesized. The peptides bound quaternary ammonium salts as guests in CDCl3. For every guest, the binding constant K of the peptide host which has a 3,5-dimethylphenyl group was larger than that of the host which has a phenyl group. ROESY analysis of the complex revealed that the N+-CH3 groups of the guests were close to the aromatic moieties of the host in the complex. The charge in cation guests, the φ-basicity of the host, and the turn conformation of the peptides were important factors for the complexation.
- Yanagihara, Ryoji,Katoh, Masaki,Hanyuu, Masayuki,Miyazawa, Toshifumi,Yamada, Takashi
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p. 551 - 556
(2007/10/03)
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- Fungicidal and bactericidal method
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A fungicidal and bactericidal method of imparting fungicidal and bactericidal properties to an article by coating or impregnating the article with a solution of a quaternary ammonium salt of alginic acid or carboxymethyl cellulose (which is insoluble or sparingly soluble in water) in an organic solvent and thereafter removing the solvent from the article.
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- Origins of Micellar Diastereoselectivity
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Thiol-functionalized surfactant micelles (n-C12H25N+Me2CH2CH2SH,Cl-) were used to cleave Z-Trp-Pro p-nitrophenyl dipeptide esters.Marked kinetic diastereoselectivity was observed in these reactions.For example at pH 8 and concentrations (ca.6-7)x1E-3 M, the micellar thiol cleaved the LL substrate 5-6 times more rapidly than its DL diastereomer.This kinetic diastereoselectivity was shown to develop at surfactant concentrations ca.5x1E-3 M, considerably above the cmc (ca.1x1E-3 M), i.e., at a second "critical concentration".Dynamic light-scattering measurements showed that micelles which had reacted with the LL (but not the DL) substrate underwent a marked increase in apparent hydrodynamic diameter (from ca. 15 to 26 nm) near this second critical concentration.Similar phenomena could be induced upon addition of 2x1E-5 M LL dipeptide surfactant reaction product to the thiol micelles.Micelles of n-C12H25N+Me2CH2CH2OH,Cl- or n-C12H25N+Me3,Cl- were unresponsive to such additions (light scattering).The results are discussed in terms of molecular and supramolecular interactions between surfactant and solubilizate molecules.
- Moss, Robert A.,Chiang, Yuan-Ching P.,Hui, Yongzheng
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p. 7506 - 7513
(2007/10/02)
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