The surface science of titanium dioxide

This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-, and δ-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and functional resemblance to the tocopherols.

The chemistry and antioxidant properties of tocopherols and tocotrienols

Dehydrogenation as a substrate-activating strategy in homogeneous transition-metal catalysis.

Mechanisms of the H2-hydrogenation and transfer hydrogenation of polar bonds catalyzed by ruthenium hydride complexes

Ruthenium-Catalyzed Reactions for Organic Synthesis.

The homogeneous olefin metathesis of 2-heptene with a catalyst system of WCl6-Bu4Sn was investigated. The optimum ratios of Bu4Sn to WCl6 were in the wide range of 1.02.0, and the Friedel-Crafts products were less than 3% when the ratios were more than 1.0. The addition of ether to the reaction medium has a relatively little influence on the catalyst activity. Bu3SnCl and Bu2SnCl2 were not effective as the cocatalyst and the decrease of the conversion with the excess amount of Bu4Sn was not significant. It therefore seems likely that Bu4Sn can provide only one alkyl group for the substitution of WCl6 and the substitution attains equilibrium in the first step of the catalyst formation.

Olefin Metathesis. I.

Transfer hydrogenation and transfer hydrogenolysis. V. Hydrogen transfer from amines, ethers, alcohols, and hydroaromatic compounds to olefins catalyzed by chlorotris(triphenylphosphine)rhodium(I)

Transfer hydrogenation and transfer hydrogenolysis. IX. Hydrogen transfer from organic compounds to aldehydes and ketones catalyzed by dihydridotetrakis(triphenylphosphine)ruthenium(II)

Transfer hydrogenation and transfer hydrogenolysis. II. Catalytic activity of some soluble complexes in hydrogen transfer from alcohols to olefins and the mechanism of the reaction catalyzed by hydridotetrakis(triphenylphosphine)rhodium(I)

Hydrogen transfer from 1,4-dioxane to olefins catalyzed by s and dioxene were formed from olefins and dioxane. After the reaction, the dioxane complex, RhCl(PPh/sub 3/)/sub 2/C/sub 4/H/sub 8/O/sub 2/, was isolat ed. The large value of the kinetic isotope effect, R/sup H/R/sup D/ = 3.1, in the use of octadeuteriodioxane and the kinetic result showed that the rate-determining step of the reaction is the dehydrogenation, that is, the formation of othe monohydride complex, RhCSTAH(C/sub 4/H/sub 7/O/sub (PPh/sub 3/)/sub 2/, by the oxidative addition of dioxane by the cleavage of a C-H bond. (auth)

Transfer-hydrogenation and transfer-hydrogenolysis. III. Hydrogen transfer from dioxane to olefins catalyzed by chlorotris(triphenylphosphine)rhodium(I)

Kazuo Fukuzumi

Papers

Olefin Metathesis. I.

Transfer hydrogenation and transfer hydrogenolysis. V. Hydrogen transfer from amines, ethers, alcohols, and hydroaromatic compounds to olefins catalyzed by chlorotris(triphenylphosphine)rhodium(I)

Transfer hydrogenation and transfer hydrogenolysis. IX. Hydrogen transfer from organic compounds to aldehydes and ketones catalyzed by dihydridotetrakis(triphenylphosphine)ruthenium(II)

Transfer hydrogenation and transfer hydrogenolysis. II. Catalytic activity of some soluble complexes in hydrogen transfer from alcohols to olefins and the mechanism of the reaction catalyzed by hydridotetrakis(triphenylphosphine)rhodium(I)

Transfer-hydrogenation and transfer-hydrogenolysis. III. Hydrogen transfer from dioxane to olefins catalyzed by chlorotris(triphenylphosphine)rhodium(I)