In the Fischer esterification reaction a carboxylic acid reacts with an excess of alcohol in acidic conditions to form an ester. During the reaction the sp2 hybridized carbonyl carbon of the acid forms an sp3 hybridized intermediate before returning to sp2 hybridization in the product. Draw the structure of the neutral sp3 hybridized intermediate and the ester product in the reaction between pentanioc acid and n-propanol. Which reactant provides the oxygen atom found in the ester linkage: Pentanoic acid, or propanol?