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LED 照射下での TiO2-装飾された光触媒からクリーンな水素の生産のためのアルコールの酸化脱水を促進する

  • 0Univ Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, ISCR - UMR6226, Rennes F-35000, France.

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Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide 02:44

10.8K

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.

Syn Dihydroxylation Mechanism
The reaction comprises a two-step mechanism. It begins with the addition of osmium tetroxide across the alkene double bond in a concerted manner forming a...

Reduction of Alkenes: Catalytic Hydrogenation 02:13

12.5K

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation 02:17

3.4K

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Oxidation of Alkenes: Syn Dihydroxylation with Potassium Permanganate 02:21

13.0K

Alkenes can be dihydroxylated using potassium permanganate.  The method encompasses the reaction of an alkene with a cold, dilute solution of potassium permanganate under basic conditions to form a cis-diol along with a brown precipitate of manganese dioxide.

The mechanism begins with the syn addition of a permanganate ion (MnO4−) across the same side of the alkene π bond, forming a cyclic manganate ester intermediate. Next, the hydrolysis of the cyclic ester with water gives a cis-diol...

Reduction of Alkynes to <em data-lazy-src=

8.1K

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Thermodynamic Stability
Catalytic hydrogenation reactions help evaluate the relative thermodynamic stability of hydrocarbons. For example, the heat of hydrogenation of acetylene is −176 kJ/mol, and that of ethylene is −137 kJ/mol. The higher exothermicity...

Oxidation of Alcohols 02:37

13.5K

In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:

(i) loss of one or more electrons,
(ii) loss of hydrogen,
(iii) addition of oxygen.

Oxidation is the opposite process of reduction, and hence, as carbonyls are reduced to alcohols, alcohols are oxidized to...