Secondary alcohols, dehydration esterification

In general, the reactions of the perfluoro acids are similar to those of the hydrocarbon acids. Salts are formed with the ease expected of strong acids. The metal salts are all water soluble and much more soluble in organic solvents than the salts of the corresponding hydrocarbon acids. Esterification takes place readily with primary and secondary alcohols. Acid anhydrides can be prepared by distillation of the acids from phosphoms pentoxide. The amides are readily prepared by the ammonolysis of the acid haUdes, anhydrides, or esters and can be dehydrated to the corresponding nitriles (31). 

The most important reactions taking place on the hydroxy groups of alcohols are 0-H bond cleavage and C-O bond cleavage. With the O-H bond cleavage, reactions with strong acids proceed, as do oxidations of primary alcohols to aldehydes, secondary alcohols to ketones and reactions with organic acids (formation of esters). In foods the last three reactions are particularly important, and are usually enzymatically catalysed. Other important reactions are dehydration and the opposite reaction, hydration, which yield unsaturated hydrocarbons from alcohols and isomeric alcohols from unsaturated hydrocarbons, respectively. These reactions are particularly important in terpenic alcohols. In oleochemistry, oxidation and esterification reactions are used for the production of various lipid derivatives. 

In addition, trifluoracetic anhydride has been a useful acid catalyst for the esterification of phenols. The use of heavy metal salts as effective esterification catalysts has been widely reported. For example, BuSnOjH and BujSnO are equal or superior to p-MeC6H4S03H as esterification catalysts and do not effect appreciable dehydration of secondary alcohols. It has been reported that catalytic activities generally descend in the order Sn, Co" , Fe" , Al, Bi, Cr, Sn", Cu, Co Pb, Fe+ Zn, Ni, Mn, Cd, Mg, Ba, K, and CIO4, SO4, PhSOj, Cl, Zr, I, NO3. The use of 1 wt% of Fe2(S04)3 is recommended as a noncorrosive catalyst in steel. 

In general, the acid catalyzed esterification of organic acids can be accomplished easily with primary or secondary alkyl or aryl alcohols, but tertiary alcohols usually give carbonium ions which lead to dehydration. The structure of the acid is also of importance. As a rule, the more hindered the acid is alpha to the carbonyl carbon the more difficult esterification becomes (20A). 

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