Hybrid orbitals of carboxylic acids

The C-O single bond of a carboxylic acid is shorter than the C—O single bond of an alcohol. This can be explained by looking at the hybridization of the respective carbon atoms. In the alcohol, the carbon is sp hybridized, whereas in the carboxylic acid the carbon is sp hybridized. As a result, the higher percent -character in the sp hybrid orbital shortens the C-O bond in the carboxylic acid. 

In both carboxylic acids and esters, the C=0 n bond is formed by the overlap of two sp hybrid orbitals, one on the oxygen atom and one on the carbon atom. The C—O O bond forms between an sp -hybridized oxygen and the carbonyl carbon. 

Hunsdiecker reaction conversion of a carboxylic acid into an alkyl halide by heating a heavy metal salt of the carboxyhc acid with bromine or iodine, hybrid orbital an orbital formed by mixing (hybridizing) orbitals. 

Problem 16.4 Write resonance structures for the COOH group and show how these and orbital hybridization account for (a) polarity and dipole moments (1.7-1.9D) of carboxylic acids (b) their low reactivity toward nucleophilic additions, as compared to carbonyl compounds.  

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