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脂肪酸からシリカへの熱分解によるケテンの形成における表面複合体の役割:プラットフォーム分子から廃棄物バイオマスへ

  • 0School of Dentistry, Cardiff University, Heath Park, Cardiff CF14 4XY, U.K.
Journal of the American Chemical Society +

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2023年12月4日

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Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction 01:22

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The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.

The reaction is a two-step process. The mechanism is still under study, but for some reagent...

Catalysis 02:50

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The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.

The illustrated image represents the reaction diagrams for an endothermic chemical process progressing in the absence (red curve) and presence (blue curve) of a catalyst.

Ketones with Nonenolizable Aromatic Aldehydes: Claisen–Schmidt Condensation 01:01

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Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the presence of an aqueous base forms a single crossed product. This reaction is referred to as Claisen–Schmidt condensation.
As the self-condensation of ketones is generally not favored in basic conditions, the self-condensed products do not form in the reaction between ketones and benzaldehyde. The general reaction of Claisen–Schmidt...

α-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview 01:19

2.9K

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester molecules in the presence of sodium metal in an aprotic solvent yields an α-hydroxy ketone product. The α-hydroxy ketone is also called acyloin, so the reaction is referred to as ‘acyloin condensation.’

In the acyloin condensation reaction, esters are converted to ketyls, which undergo radical dimerization to form an unstable...

Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration 02:40

8.5K

Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.       

Since the rate of acid-catalyzed hydration of alkynes is much slower than alkenes, a mercuric salt like mercuric sulfate (HgSO4) is usually added to facilitate the reaction. Hydration of terminal alkynes follows Markovnikov's rule;...

Preparation of Aldehydes and Ketones from Alcohols, Alkenes, and Alkynes 01:33

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Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for synthesizing aldehydes and ketones. The conversion of alcohol to aldehyde, which involves the oxidation process, depends on the class of the alcohol used and the strength of the oxidizing agent. For instance, primary alcohol will form an aldehyde when treated with a weak oxidizing agent; however, it gets over-oxidized to a carboxylic acid in...