Given the following compounds: C2H4 (ethene), C2H2 (acetylene), and C2H6 (ethane), rank them from the fastest rate of hydration to the slowest rate.

• A. C2H6 > C2H4 > C2H2
• B. C2H2 > C2H6 > C2H4
• C. C2H4 > C2H2 > C2H6
• D. C2H2 > C2H4 > C2H6

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the reaction type — hydration of alkenes and alkynes involves the addition of water (H\_2O) across the multiple bonds (double or triple bonds) in the molecule, typically catalyzed by an acid.
2. Step 2: Identify the types of bonds in each compound: C\_2H\_6 (ethane) has only single bonds (alkane), C\_2H\_4 (ethene) has a double bond (alkene), and C\_2H\_2 (acetylene) has a triple bond (alkyne).
3. Step 3: Recall that the rate of hydration depends on the bond type; double bonds (alkenes) are generally more reactive toward electrophilic addition reactions like hydration than triple bonds (alkynes), and single bonds (alkanes) are the least reactive.
4. Step 4: Consider the stability of the intermediate carbocation formed during the hydration mechanism; alkenes form more stable carbocations compared to alkynes, which influences the rate of reaction.
5. Step 5: Based on bond reactivity and intermediate stability, rank the compounds from fastest to slowest hydration rate as: C\_2H\_4 (ethene) > C\_2H\_2 (acetylene) > C\_2H\_6 (ethane).