Ketonization of carboxylic acids

Zeolite H-T catalyzed the ketonization of short-chain carboxylic acids. The formation of anhydrides is a side reaction, occurring on the outer surface of the zeolite ctystals. The propionic and butyric acid molecules seem to have the optimum size for a bimolecular ketonization reaction inside an erionite cavity. The ketonization of carboxylic acids is an example of zeolite specificity in catalysis, illustrating the necessity of strict adaptation of the transition state of the reaction to the intracrystalline porosity of the zeolite. 

A review on cage and window effects in mainly hydroconversion of alkanes with zeolites [73] shows that bi- and even trinodal distributions of product carbon numbers can be formed. In the erionite (ERI) cage Cs hydrocarbon fragments are selectively trapped, thus undergoing intense secondary cracking. This effect was confirmed in the ketonization of carboxylic acids [74]. Alternatively, in cases of slow diffusion (and counterdiffusion), viz. in the liquid-phase propylation of benzene in mordenite, the possibihty of having pore-mouth catalysis was advanced [75]. Multinodal product distributions from... 

Symmetric and nonsymmetric ketones have been obtained by the ketonization of carboxylic acids (Eq. 13.1) or ethyl esters (Eq. 13.2) in the gas phase over ceria-based catalysts under flowing conditions ... 

The most general synthetic route to ketones uses the reaction of carboxylic acids (or their derivatives) or nitriles with organometallic compounds (M.J. Jorgenson, 1970). Lithium car-boxylates react with organolithium compounds to give stable gem-diolates, which are decom-... 

A classical way to achieve regioselectivity in an (a -i- d -reaction is to start with a-carbanions of carboxylic acid derivatives and electrophilic ketones. Most successful are condensations with 1,3-dicarbonyl carbanions, e.g. with malonic acid derivatives, since they can be produced at low pH, where ketones do not enolize. Succinic acid derivatives can also be de-protonated and added to ketones (Stobbe condensation). In the first example given below a Dieckmann condensation on a nitrile follows a Stobbe condensation, and selectivity is dictated by the tricyclic educt neither the nitrile group nor the ketone is enolizable (W.S. Johnson, 1945, 1947). 

Reduction of Aldehydes, Ketones, and Carboxylic Acid Derivatives... 

The next several chapters deal with the chemistry of various oxygen containing func tional groups The interplay of these important classes of compounds—alcohols ethers aldehydes ketones carboxylic acids and derivatives of carboxylic acids— IS fundamental to organic chemistry and biochemistry... 

Although the present chapter includes the usual collection of topics designed to acquaint us with a particular class of compounds its central theme is a fundamental reaction type nucleophilic addition to carbonyl groups The principles of nucleophilic addition to aide hydes and ketones developed here will be seen to have broad applicability m later chap ters when transformations of various derivatives of carboxylic acids are discussed... 

The haloform reaction is sometimes used for the preparation of carboxylic acids from methyl ketones... 

We ve seen how Grignard reagents add to the carbonyl group of aldehydes ketones and esters Grignard reagents react m much the same way with carbon dioxide to yield mag nesium salts of carboxylic acids Acidification converts these magnesium salts to the desired carboxylic acids... 

Esterification of carboxylic acids involves nucleophilic addition to the carbonyl group as a key step In this respect the carbonyl group of a carboxylic acid resembles that of an aldehyde or a ketone Do carboxylic acids resemble aldehydes and ketones m other ways Do they for example form enols and can they be halogenated at their a carbon atom via an enol m the way that aldehydes and ketones can ... 

The first stage of the mechanism is exactly the same as for nucleophilic addition to the carbonyl group of an aldehyde or ketone Many of the same nucleophiles that add to aldehydes and ketones—water (Section 17 6) alcohols (Section 17 8) amines (Sections 17 10-17 11)—add to the carbonyl groups of carboxylic acid derivatives... 

ARNDT EISTERT Homoiogation Homologalion of carboxylic acids or ketones... 

Theperfluoroorganozmc compounds have limited application in organic syn thesis because of their lack of reactivity However, heptafluoro I methylethylzinc iodide reacts with acyl fluorides or anhydrides of carboxylic acids in the presence of pyndine to give the corresponding ketones [7S] (equations 28 and 29) In the presence of zinc fluoride, acyl chlorides can be used as substrates [7d]... 

Alkenes are cleaved to carbonyl compounds by ozonolysis. This reaction is useful both for synthesis (preparation of aldehydes, ketones, or carboxylic acids) and analysis. When applied to analysis, the carbonyl compounds are isolated and identified, allowing the substituents attached to the double bond to be deduced. 

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