Final answer:
Transesterification is a chemical reaction where an ester and an alcohol react to form a new ester and a byproduct alcohol. It is commonly used in biodiesel production. The reaction is reversible and can be catalyzed by acids or bases. The correct answer is 3) The ester and alcohol react to form a new ester.
Step-by-step explanation:
Transesterification is a type of reaction that occurs between an ester and an alcohol. During this chemical process, the ester and alcohol react to form a new ester along with a byproduct, which is often another alcohol. In the context of biodiesel production, a triglyceride (a type of ester) reacts with methanol to produce glycerol and a new methyl ester. This methyl ester is the biodiesel itself. Transesterification is an example of an acyl substitution reaction where the alcohol acts as a nucleophile, attacking the ester which is the electrophile.
For instance, when methanol (CH3OH) reacts with ethyl acetate (CH3CH₂OCOCH₃), the products are a new ester, methyl acetate (CH3OCOCH3), and another alcohol, ethanol (CH3CH₂OH). This reaction can be catalyzed by an acid or a conjugated base of the alcohol. It is considered a reversible reaction, and the equilibrium can be shifted by altering reactant or product concentrations. Therefore, The correct answer is 3) The ester and alcohol react to form a new ester.