New trends and techniques of the electrochemical method are reviewed to show readers how electrochemical methods gave impact to a variety of problems in today's chemistry. An emphasis was given to demonstrate the feasibility of the electrochemical method to study what can not be solved with other methods. Contents of the present review are as follows : 1) What is the electrochemical method ?, 2) Measurements and apparatus, 3) Sample preparations, 4) Problems associated with electrochemical methods, 5) Functional electrodes, 6) Determination of thermodynamic constants, 7) New types of electrochemical reactions, and 8) Future.
Electrophilic oxygenation studies of C-H bond in organic compounds, particullary in alkanes, with ozone and/or hydrogen peroxide in super acid solutions, established recently in Prof. G.A. Olah's laboratory, were reviewed. The reactions, giving oxyfunctionalized products, can be well explained to proceed via initial electrophilic attack toward the σ-bonds in alkanes by protonated ozone, i. e., O3+H and/or hydroperoxonium ion, i. e., H3+O2 to give the pentacoordinated carbonium ion as transition state. The reaction behaviors of single σ-bonds in functionalized organic compounds, such as alcohol, ketones etc, were also described from the view point of organic synthesis.
The mechanisms of various Pummerer type reactions of sulfoxides and other trivalent sulfur compounds, such as sulfilimines and sulfonium ylides, are critically analyzed and discussed based on numerous observations on both stereochemistry and kinetic experiments together with 18O and D tracer experiments. Several stereospecific reactions are described. Particularly interesting is an asymmetric induction to α-carbon in the reaction of optically active sulfoxides with acetic anhydride which is considered to proceed through an exclusively intramolecular acetoxy migration via an intimate ion-pair derived by S-O bond cleavage of the incipient acetoxysulfonium ylide formed in the early stage of the reaction. Several examples of intramolecular Pummerer reactions and many other Pummerer reactions which proceed via an ion-pair process are also given. Finally, the Pummerer reaction for a model pathway for enzymatic oxidative demethylation of methionine is briefly described.
Peripheral conjugate carbo- and heterocycles such as bridged homo- and heteroannulenes, cyclazines, and dihydropyrenes are desired in order to obtain experimental evidence regarding our recognition of the net energy changes associated with π-electron delocalizations. In this review is described the chemistry of cyclazines, a novel class of compounds consisting of a π perimeter bridged by a central sp2-hybridized nitrogen atom; 1. Introduction, 2. Synthesis and Properties of Cyclazines, 3. Reactions of Cyclazines, 4. Molecular Orbital Treatment of Cyclazines and Electron Paramagnetic Resonance Study of Their Radical Ions.
The liquid phase hydrogenation of alkenes and cycloalkenes over nickel-phosphorus catalyst (Ni-P) was investigated under atmospheric pressure and room temperature. Hydrogenation proceeds smoothly when the Ni-P is treated with hydrogen before the addition of the substrate. The rate of hydrogenation depends on the ring size (cyclopentene, 1.00; cyclooctene, 0.37; cyclohexene, 0.15) and the number of substituents on the double bond (1-hexene, 1.00; 3-hexene, 0.34; 2-methyl-2-pentene, 0.10; 2, 3-dimethyl-2-butene, 0.04). These results showed a close analogy with those of hydrogenation over P-2 nickel boride catalyst. D-Limonene was hydrogenated selectively to p-menthene- (1) (960) over Ni-P.
Effects of immersion time of the catalyst in tartaric acid solution for modification on the asymmetric activity of the modified catalyst were investigated in the hydrogenation of methyl acetoacetate. It was found that, in order to prepare highly asymmetrically active catalyst, the immersion of the catalyst for 69 hours on a hot water bath was necessary. Thus, when the catalyst immersed for 6 hours was used, the greatest asymmetric selectivity (optical yield=99%) was obtained in the hydrogenation in tetrahydrofuran and a small amount of formic acid.
Recent advances of the chemistry of vinyl anions stabilized by heteroatoms, such as oxygen, sulfur, silicon and halogen atoms are reviewed, especially focusing on the methods of their generation and the reaction with electrophiles.
Isopropanol was originally produced by indirect hydration of propylene using sulfuric acid. This method has still been applied by many factories ever since 1920. But the problems of corrosion, a high heat requirement and pollution called for the deveropment of direct hydration routes. A great number of research have been done on direct hydration of propylene for many years. It is quite lately, however, that Vaba Chemie, Deutsche Texaco and Tokuyama Soda have independently developed new economical direct hydration methods and applied them to the commercial production of isopropanol. Reportedly, Vaba Chemie's gas-phase hydration process employs a fixed-bed of supported phosphoric acid catalyst. Deutsche Texaco's process works in vapor-liquid mixed phase using a cation exchange resin catalyst. Tokuyama Soda's liquid-phase hydration method adopts a tungsten-type solution catalyst system. It is expected that these three processes will be greatly helpfull in promoting the technology shift from indirect method to direct one for isopropanol manufacturing.