Stereoselective hydrolysis of p-nitrophenyl N-acyl-D (L) -phenylalaninates by the bilayer and micellar catalytic systems of L-histidine derivatives and surfactants were performed. The noteworthy aspects are as follows : (a) According to the isokinetic temperature (β), the hydrolysis of enantiomer substrates in the bilayer systems might be entropy-driven (β<T (average value of experimental temperatures)), whereas that in the micellar systems might be enthalpy-driven (β>T). The stronger hydrophobic microenvironment of the bilayer systems would probably be connected with the entropy-driven nature ; (b) the enantioselectivity was markedly elevated at temperatures somewhat higher than the phase transitions in the bilayer systems; (c) the enantioselectivity was fairly enhanced by addition of cholesterol and micelles in the bilayer systems, and it would be attributed to the change of hydrophobic microenvironments on the basis of the β value in connection with T.
This article deals with syntheses of various types of condensation polymers by two-phase polycondensation using phase transfer catalysis (PTC). The scope of this article encompasses (i) synthesis of polyesters and their analogs such as aromatic polyesters, polysulfonates, polyphosphonates, and polythioesters by PTC nucleophilic acyl substitution ; (ii) synthesis of condensation polymers such as polyethers, polysulfides, carbon-carbon chain polymers, and polyamine derivatives by the application of PTC alkylation ; and (iii) synthesis of polyesters and their analogs such as polycarbonates, polyesters, and polysulfones by PTC nucleophilic aliphatic substitution. Some factors influencing these PTC polymer syntheses are discussed and comparison of this method with other synthetic methods are also presented.
This review article discusses the mode and probe of the solvent participation in the organic reactions. Emphases are given to the elementary rate processes and also to the indirect participation of solvent clusters. Discussions are given in the order : 1) General background. 2) Empirical LFER with solvent parameters. 3) Thermochemical approach. 4) Information from the gas-phase reactions. 5) Significance of the solvent molecule reorganization during the activation process of the liquid-phase reactions. 6) Examples and the mode of solvent participation. This review does not aim the comprehensive coverage of the current awareness of the solvent effect but tries to point out the importance of the insight of the microscopic view of the total solution system where the reaction is taking place.
For the purpose of the assignment of 1H and 13C NMR spectra, useful techniques of the measurement are summarized. At first, the methods are shown to change the chemical and physical environment. Next one-dimensional pulse techniques such as INEPT, DEPT, and GASPE are interpreted. Then two-dimensional NMR, mainly COSY and 13C-1H shift correlated 2D NMR are explained, where the main purpose is to show the practical ways how to understand, measure, and assign the 2D-NMR spectra.
The Halcon SD Group, founded in 1946 by Dr. R. Landau with a few friends, discovered and developed the break-through processes, such as direct vapor phase ethylene oxidation to ethylene oxide, production of terephthalic acid and related products by liquid phase oxidation, boric acid-assisted oxidation of cycloparaffins to KA oil, and co-production of propylene oxide and t-butyl alcohol/styrene, etc. The Group has contributed an estimated one-fourth of the petrochemical industry's major process discoveries. Worldwide, the industry uses its technologies to manufacture some ten million tons of products annually. Why the Group succeeded ? To answer the question, a brief history is described, focussing the thought and deed of Dr. Landau.
MT-sulfone is the abbreviation for methylthiomethyl p-tolyl sulfone (1), which is easily obtainable from DMSO in one-pot manner : treatment of DMSO with acetic anhydride followed by the reaction of the resulting acetoxymethyl methyl sulfide with sodium p-toluenesulfinate in acetic acid. This reagent is thermally stable and less hygroscopic, and a carbanion can be generated on the central carbon of 1 with an easily handled base such as sodium hydride or sodium hydroxide-TOMAC (a phase transfer catalyst). Hence MT-sulfone (1) has been revealed to be an efficient reagent for preparing many kinds of organic compounds such as carboxylic esters, S-methyl carbothioate, aldehydes, acyclic and cyclic ketones, α-alkoxy-α-arylacetic esters, S-methyl α-ketocarbothioate, and various derivatives of 2-methoxycarbonyl-1, 4-cyclohexanedione.