Can citric acid create a polyester?
The esterification of carboxylic acids with tertiary alcohols usually occurs by an SN1 mechanism wherein the oxygen of the alcohol is protonated and a tertiary carbocation is formed. It in turn reacts with the carboxylic acid to form the tertiary ester. The hydroxyl group in citric acid, while tertiary, is alpha to a carboxyl group. A cation alpha to a carboxyl group (-CO2H) is a destabilized entity. This mechanism would be precluded. Traditional Fischer esterification is likely sluggish owing to steric hinderance.