Carboxylic acid from alkylbenzenes

Show how to synthesize carboxylic acids from oxidation of alcohols and aldehydes. Problems 20-36, 39, and 44 carboxylation of Grignard reagents, oxidative cleavage of alkenes and alkynes, hydrolysis of nitriles, and oxidation of alkylbenzenes. 

The newer HFC refrigerants are not soluble in or miscible with mineral oils or alkylbenzenes. The leading candidates for use with HFC refrigerants are polyol ester lubricants. These lubricants are derived from a reaction between an alcohol and a normal or branched carboxylic acid. The most common alcohols used are pentaerythritol, trimethylolpropane, neopentylglycol, and glycerol. The acids are usually selected to give the correct viscosity and fluidity at low temperatures. 

Skubla [9] has designed a group contribution scheme which applies for various homologous series. His method relies on eq. 6.2.1 where both coefficients a0 and a have to be derived from group contributions and with respect to Nc. The model applies for n-alkanes, 1-alkenes, n-alkylcyclopentanes and n-alkylcyclohexanes, alkylbenzenes, 1-bromoalkanes, 1-alkanols, di-n-alkyl ethers, carboxylic acids and esters, 1-alkanethiols, 1-aminoalkanes, dialkylamines, alkaneamides, and some... 

Carboxylic acids can be obtained from most alkylbenzenes b" oxidation of the side chain with reagents such as potassium permanganate, potassium dichromate, or nitric acid ... 

Decarboxylation of alkanoic acids means of LTA in benzene as solvent is hindered by die formation of all lbenzenes as by-products. This side reaction is especially pronounced widi radicals derived from primary acids or odier acids from which the radical is not easily oxidized LTA. In some cases, such as that of apocamphane-l-carboxylic acid (equation 54), good yields of alkylbenzene can be obtained. Intramolecular versions of this reaction in which the radical cyclizes onto an aromatic nucleus at the appropriate position in the chain have also been observed. 

For example, an aldehyde prepared by the oxidation of a primary alcohol (Sec. 16.8) may very well be contaminated with the carboxylic acid this acid can be simply washed out with dilute aqueous base. The carboxylic acid prepared by oxidation of an alkylbenzene (Sec. 12.10) may very well be contaminated with unreacted starting material the carboxylic acid can be taken into solution by aqueous base, separated from the insoluble hydrocarbon, and regenerated by addition of mineral acid. 

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