Final answer:
An anhydride is formed when the carboxyl group from a fatty acid combines with an alcohol, resulting in the formation of an ester and water as a by-product. Option 1 is correct.
Step-by-step explanation:
An anhydride is formed when the carboxyl group from a fatty acid combines with an alcohol. The -OH group of the carboxyl group is replaced by the -OR' group of the alcohol to form an ester. The reaction also produces water as a by-product. Therefore, the correct answer is 1) Alcohol.
For an anhydride to form, the carboxyl group from the fatty acid would need to combine with an alcohol. This reaction occurs when the -OH group of the carboxylic acid is replaced by the -OR' group of the alcohol, to form an ester. Acid anhydrides can react with alcohols to produce one equivalent of ester and one equivalent of carboxylic acid, whereas reacting with amines would produce an amide and an amine salt of the carboxylic acid, not an anhydride. For instance, ethyl acetate is an ester formed when acetic acid reacts with ethanol. Aldehydes and ketones, which also contain a carbonyl group, do not react with carboxylic acids in a way that would produce an anhydride.