Kolbes reaction

Athanasios I. Papadopoulos, ... Panos Seferlis, in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, 2018 QM models in reactive systems Stanescu and Achenie 414 and Stanescu et al. 415 propose a QM-CAM RD approach for the identification of solvents that create a homogeneous reaction mixture, while at the same time promote the Kolbe–Schmitt reaction. DFT calculations are used to confirm the reaction mechanism, and to compute the energies and thermodynamic properties of the optimized structures and transitions states along the reaction path. Solvents are designed using GC-CAMD and few of them are selected for calculation of the reaction rate constant using the transition-state theory. The QM calculations are therefore used as a final step, after the solvents have been designed. In a different line of work, Hechinger et al. 416 propose the combination of reaction network flux analysis (RNFA) 417 with CAMD for the identification novel biofuels and chemical pathways of producing them. CAMD is used in a strategy where optimum molecules are identified based on properties which point toward useful fuels. Then, a reaction network toward these components is constructed in order to identify and compare suitable production routes. A different strategy is also considered where fuel-related properties are calculated for all molecules in a prespecified reaction network and are then employed as performance criteria in order to identify target molecules and the co...

P.W.G. SMITH PH.D., D.I.C., A.R.C.S., A.R.I.C., A.R. TATCHELL M.SC., PH.D., F.R.I.C., in Aromatic Chemistry, 1969 B.5FURTHER SUBSTITUTION REACTIONS The Kolbé reaction.That the carboxyl group can be introduced directly into a phenol nucleus by passing carbon dioxide over the heated sodium phenoxide was first observed by Kolbé. Substitution occurs predominantly in the ortho position. Salicylic acid is manufactured by carrying out the reaction under pressure at about 150° (the Kolbé-Schmidt process).Some of the isomeric p-hydroxybenzoic acid is also obtained and its proportion in the product increases when the reaction is carried out at higher temperatures. Hydroxymethylation.Condensation of phenols with aldehydes takes place readily in the presence of either acidic or basic catalysts. The most important example is the reaction between phenol and formalin, usually carried out in the presence of aqueous sodium hydroxide, which gives a mixture of o-and p-hydroxybenzyl alcohols. Cross linking of the “resols” can occur under suitable conditions forming rigid three-dimensional polymers which are the synthetic “plastics” (phenol-formaldehyde resins) of the “Bakelite” type. Coupling with diazonium salts.The introduction of an arylazo group by reaction of phenols with diazonium salts is discussed on p. 138. Pyridin-2-one undergoes the Kolbe reaction with carbon dioxide under pressure to give a good yield of the 5-carboxylic acid (60%). Pyridin-4-one also reacts readily to give 3-mono...

Kolbe reaction, also known as Kolbe Schmitt Reaction is a type of addition reaction named after Hermann Kolbe and Rudolf Schmitt. When phenol is treated with sodium hydroxide, phenoxide ion is generated. The phenoxide ion generated is more reactive than phenol towards electrophilic aromatic substitution reaction. Hence, it undergoes electrophilic substitution reaction with carbon dioxide, which is a weak electrophile. Ortho-hydroxybenzoic acid (salicylic acid) is formed as the primary product. This reaction is popularly known as Kolbe’s reaction. Categories • • (31.9k) • (8.8k) • (764k) • (248k) • (2.9k) • (5.2k) • (664) • (121k) • (72.1k) • (3.8k) • (19.6k) • (1.4k) • (14.2k) • (12.5k) • (9.3k) • (7.7k) • (3.9k) • (6.7k) • (63.8k) • (26.6k) • (23.7k) • (14.6k) • (25.7k) • (530) • (84) • (766) • (49.1k) • (63.8k) • (1.8k) • (59.3k) • (18.5k) • (1.5k) • (1.9k) • (4.3k) • (188) • (194) • (259) • (211) • (315) • (176) • (183) • (283) • (256) • (369) • (369) • (376) • (349) • (332) • (311) • (1.3k) • (1.4k) • (867) • (1.0k) • (1.5k) • (812) • (1.2k) • (1.7k) • (965) • (18.6k) • (6.1k) • (3.7k) • (4.4k) • (4.2k) • (3.8k) • (24.5k)

Contents • How do you prepare ethane by Kolbe’s electrolytic method? • Can we prepare alkanes by Kolbe’s electrolytic method? • How alkanes are formed? • What reaction is used to prepare alkanes? • Which Electrophile is used in Kolbe reaction? • How do you convert Ethyne into ethene? • What do you mean by Kolbe’s reaction? • Is cell an electrolytic? • How is chlorine prepared by electrolytic method diagram? • What is electrolytic refining of metals? • What is decarboxylation reaction give an example? • Why methane is not prepared by Kolbe’s electrolytic method? • What is Frankland reaction? • How do you convert ethyne into benzene? • How do you convert ethyne to acetaldehyde? • How does ethene produce crude oil? • Which product is obtained by Kolbe’s reaction? • What is Kolbe’s reaction with example? • What is action of of nitrating mixture on phenol? • What are alkanes give two methods of preparation? • How is methane prepared? • How do I make alkyne? In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. How do you prepare ethane by Kolbe’s electrolytic method? For example by, Kolbe’s electrolytic method, electrolysis of aqueous solution of potassium acetate gives ethane. At anode acetate ion forms acetate free radical. ...

The Kolbe synthesis reaction, also known as the Kolbe electrolysis or the Kolbe-Schmitt reaction, is an organic synthesis reaction that was discovered in 1845 by the German chemist Hermann Kolbe. The Kolbe synthesis reaction involves the electrolysis of an aqueous solution of a salt of a carboxylic acid to produce a hydrocarbon. The mechanism of the Kolbe synthesis reaction involves the generation of carbanions at the anode of an electrolytic cell. The carbanions can then react with the solvent, water, to form hydrocarbons. The Kolbe synthesis reaction is a helpful way to produce hydrocarbons, essential in the chemical industry for use as fuels, solvents, and starting materials for synthesizing other compounds. The Kolbe synthesis reaction can be generalized by the following equation: Where R is a hydrocarbon group, such as an alkyl or aryl group, and CO 2 is carbon dioxide. The reaction occurs in an electrolytic cell with a cathode and an anode. The electrolytic cell is filled with an aqueous solution of carboxylic acid salts, such as sodium acetate or potassium benzoate. At the cathode, water is reduced to form hydrogen gas and hydroxide ions: The hydrocarbons produced by the Kolbe synthesis reaction are usually high molecular weight compounds that are difficult to isolate and purify. The reaction is also limited to carboxylic acids that are stable under the reaction conditions, which typically involve high temperatures and high current densities. The Kolbe synthesis rea...

Kolbe Electrolysis The non-Kolbé electrolysis proceeded through a carbenium ion intermediate and was assisted by the well-known stabilising effect of the β carbon–silicon bond. From: Comprehensive Organic Functional Group Transformations, 1995 Related terms: • Decarboxylation • Methyl • Alkene • Methanol • Aqueous Solution • [Alpha] • Monomer Hans J. Schäfer, in Comprehensive Organic Synthesis, 1991 2.8.2Reaction Conditions for the Kolbe Electrolysis The pathway leading to radical products ( Kolbe electrolysis) and/or cationic intermediates (nonKolbe electrolysis) is determined mainly by the substituents in the α-position of the carboxylic acid and some experimental factors. The electrolysis products of different carboxylates have been compared with the ionization potentials of the intermediate radicals. 7c From this it appeared that alkyl radicals with gas-phase ionization potentials smaller than 8eV mainly lead to carbenium ions. Accordingly, α-substituents such as carboxy, cyano or hydrogen support the radical pathway, whilst alkyl, cycloalkyl, chloro, bromo, amino, alkoxy, hydroxy, acyloxy or aryl more or less favor the route to carbenium ions. Besides electronic effects, the oxidation seems also to be influenced by steric factors. 24 Bulky substituents diminish the extent of coupling. The main experimental factors that affect the yield in the Kolbe electrolysis are the current density, the pH of the electrolyte, ionic additives, the solvent and the anode material. Hig...