An ester is a compound formed by a condensation reaction between a carboxylic acid and an alcohol that eliminates a water molecule. Read the discussion of esters in Section 24.4 and then give an example of a reaction forming an ester. How might this kind of reaction be extended to form a polymer (a polyester)?

In the condensation reaction between a carboxylic acid and an alcohol, a water molecule is eliminated, and an ester is formed. The general structure of an ester can be represented as R-COO-R', where R and R' represent different hydrocarbon chains.

Let's take acetic acid (CH3COOH) and ethanol (CH3CH2OH) as an example. The reaction between these two compounds can be represented as follows: \[ CH3COOH + CH3CH2OH \rightarrow CH3COOCH2CH3 + H2O \] In this reaction, acetic acid reacts with ethanol to form ethyl acetate (CH3COOCH2CH3) and a water molecule.

To form a polyester, we need to have a carboxylic acid with two or more carboxyl groups (-COOH) and an alcohol with two or more hydroxyl groups (-OH). These compounds are called dicarboxylic acids and diols, respectively. When a dicarboxylic acid reacts with a diol, a polyester is formed through the continuous condensation reaction between the carboxyl and hydroxyl groups, eliminating water molecules in the process. For example, let's consider the formation of a polyester called polyethylene terephthalate (PET), which is widely used in making plastics and fibers. The reaction will involve terephthalic acid (C6H4(COOH)2), a dicarboxylic acid, and ethylene glycol (C2H4(OH)2), a diol. The formation of polyester can be represented as follows: \[ n \, C6H4(COOH)2 + n \, C2H4(OH)2 \rightarrow [C6H4(COOC2H4O)]_n + 2n \, H2O \] In this reaction, a continuous chain of ester-linked terephthalic acid and ethylene glycol monomers is formed, creating the polyester PET.