Higher carboxylic acids

The auto-decomposition of lead tetraacetate in acetic acid, which normally occurs at reflux temperature , can be studied at 50 °C in the presence of sodium acetate The principal products of both the uncatalysed and catalysed decompositions are acetoxyacetic acid and carbon dioxide. The kinetic order of the normal decay of Pb(IV) is complex and evidence was obtained that oxidation of products is significant after the earliest stages. The evidence indicates that slow, simple homolytic breakage of lead tetraacetate to give Pb(OAc)3- and AcO-does not occur but that the solvent plays an integral part, e.g. 

The radical -CH2C02H is regarded as originating from the solvent. This primary step is followed by a multitude of secondary reactions. An entirely analogous scheme, producing (CH3)2CH-0-C(CH3)2, was proposed for decomposition in di-isopropylether °. 

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Another method for deallylation of ally esters is the transfer of the allyl group to reactive nucleophiles. Amines such as morpholine are used[415-417], Potassium salts of higher carboxylic acids are used as an accepter of the allyl group[418]. The method is applied to the protection and deprotection of the acid function in rather unstable /f-lactam 664[419,420]. 

Primary and secondary alkyl halides may be converted to the next higher carboxylic acid by a two step synthetic sequence involving the preparation and hydrolysis of nitriles Nitnles also known as alkyl cyanides are prepared by nucleophilic substitution... 

Eor amine-containing polymers, DMF is often a good choice of solvent. DMF can also be a good choice for polymers of higher carboxylic acid content. However, DMF does present some experimental difficulties. It must be run at an elevated temperature, typically 60°C, because of its viscosity. Also, because most polymers have a much lower refractive index response in DMF, the signal-to-noise ratio for a polymer in this solvent is diminished versus the same ratio for common acrylates in THF. 

Such reactions usually are called Brown-Walker reactions. They are of practical importance for the synthesis of higher carboxylic acids. 

Simple aliphatic carboxylic acids having upto four carbon atoms are miscible in water due to the formation of hydrogen bonds with water. The solubility decreases with increasing number of carbon atoms. Higher carboxylic acids are practically insoluble in water due to the increased hydrophobic interaction of hydrocarbon part. Benzoic acid, the simplest aromatic carboxylic acid is nearly insoluble in cold water. Carboxylic acids are also soluble in less polar organic solvents like benzene, ether, alcohol, chloroform, etc. 

Nmr information on the protonated forms of other carboxylic acids is also available and has been reviewed recently (Olah et al., 1970d). Generally, the trans-form of the protonated carboxyl group [200] predominates in higher carboxylic acids. This is probably stabilized by hydrogen-bonding. 

Carbonylation of acetic acid to higher carboxylic acids can occur in presence of ruthenium/iodide catalysts. The reaction involves reduction and several carbonylation steps. The overall reaction may be written as follows ... 

These results also demonstrate the ability of the ruthenium carbonyl iodide systems to activate both the alkyl and the acyl part of the formates. The same is true for esters of higher carboxylic acids where new esters of higher homologous acids and alcohols are produced. 

Alkyl formates or formic acid and its esters can be converted to trialkyl orthothioformates [74-77] which in turn can be converted to trialkyl orthoformates in good yields [78, 79], It has been reported that acid chlorides of higher carboxylic acids can also be converted to trialkyl orthothioformates [80], but thus far no reports appear in the literature on attempts to convert them to trialkyl ortho esters. 

FLUORINECOMPOUNDS,ORGANIC - FLUORINATED HIGHER CARBOXYLIC ACIDS] (Vol 11)... 

The acyl chloride (the crude material prepared by the thionyl chloride method is quite satisfactory) is added dropwise to well-stirred concentrated aqueous ammonia cooled in a freezing mixture. The amides of the higher carboxylic acids crystallise out on standing and need only to be filtered and recrystallised. Water-soluble amides are isolated by extraction with hot ethyl acetate following removal of water on a rotary evaporator. 

The reaction principle of the Kolbe synthesis can be extended both to higher carboxylic acids (e.g. methyl suberate228)) and to the dimerization of two different carboxylic acids (cross Kolbe coupling). A few examples of syntheses studied on the laboratory scale are listed below. 

Higher carboxylic acids Tertbutyl methyl ether — Flame ionisation Carboxylic acids derivitivised with diazomethane 5 fig L-1 [628]... 

Higher carboxylic acids Capillary column Electron capture flame ionisation Carboxylic acids derivitivised to p-bromophenacyl esters [629]... 

In 1953, Gilman and coworkers1308 proposed an unusual method for reacylation of triethylacetoxyplumbane. They found that insoluble EtsPbOOCR was immediately precipitated when an aqueous solution of triethylacetoxylplumbane was mixed with the sodium salts of higher carboxylic acids RCOONa. 

When a nucleophile containing a heteroatom reacts at a carboxyl carbon SN, reactions occur that convert carboxylic acid derivatives into other carboxylic acid derivatives, or they convert carbonic acid derivatives into other carbonic acid derivatives. When an organometallic compound is used as the nucleophile, SN reactions at the carboxyl carbon make it possible to synthesize aldehydes (from derivatives of formic acid), ketones (from derivatives of higher carboxylic acids), or—starting from carbonic acid derivatives—carboxylic acid derivatives. Similarly, when using a hydride transfer agent as the nucleophile, SN reactions at a carboxyl carbon allow the conversion of carboxylic acid derivatives into aldehydes. 

The carbonylation of alcohols to give the next higher carboxylic acid is catalyzed by nickel. Catalytic systems are based on Ni(CO)4, NiX2, or metallic nickel in the presence of a halogen (86,87). In all of these cases, though, the active species can be derived from nickel(O) species, for example... 

The homologation of acetic acid to higher carboxylic acids, especially to propionic acid, is also possible, e.g., with Ru/iodide catalysts. The reaction is thought to involve reduction and carbonylation steps, such as77... 

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