ETS Major Field Test Chemistry Practice Test

The hydration of alkynes typically leads to the formation of ketones as the major product, particularly when proceeding through a mechanism that involves the addition of water across the triple bond. This reaction is often facilitated by the presence of an acid, which protonates the alkyne to generate a more reactive intermediate. The initial addition of water results in an enol, which then rapidly rearranges through tautomerization to yield a ketone. In the case of terminal alkynes, the hydration can lead to aldehydes; however, for internal alkynes, the process predominantly yields ketones. The positioning of the carbonyl group in the final product is a direct result of the regioselectivity of the reaction, favoring the more stable carbocation intermediate. This understanding of the mechanism is vital, as it highlights the preference for ketone formation under typical hydration conditions in the presence of catalyzing acids.