Acid-catalyzed hydration is a crucial addition reaction in organic chemistry, particularly for synthesizing alcohols. This method is one of three primary ways to produce alcohols through addition reactions. The process involves the formation of a carbocation intermediate, which is a key feature of this reaction. Carbocations are known for their ability to undergo rearrangements, which can lead to unpredictable outcomes in the reaction products. This characteristic can complicate the synthesis, as the rearrangement may yield unexpected alcohols.

In terms of stereochemistry, carbocations are trigonal planar, allowing for nucleophilic attack from either side. This results in a mixture of chiral products, making the stereochemistry of the final alcohols uncertain. Acid-catalyzed hydration specifically leads to the formation of Markovnikov alcohols, where the more stable carbocation forms at the more substituted carbon atom. This is a significant aspect of the reaction, as it dictates the location of the hydroxyl group in the final product.

The reagents for acid-catalyzed hydration typically include water (H₂O) and an acid, such as sulfuric acid (H₂SO₄). The reaction can be distinguished from dehydration by examining the starting material; if a double bond is present, the reaction will proceed to form an alcohol through hydration. The mechanism mirrors that of hydrohalogenation, where water acts as the nucleophile instead of a halide ion.

In a general reaction, a double bond reacts with water and acid, resulting in the addition of an -OH group at the more substituted carbon (Markovnikov site) and an -H at the less substituted carbon (anti-Markovnikov site). The presence of a squiggly line in the product structure indicates unknown stereochemistry, suggesting that multiple stereoisomers may form, but it is not necessary to depict all possible configurations.

Overall, acid-catalyzed hydration is a predictable and essential reaction for alcohol synthesis, characterized by its reliance on carbocation stability and the Markovnikov rule for product formation.