Question

Among the following the appropriate reactants for the preparation of 1–ethyl cyclohexanol are

• A.
• B.
• C.
• D.

Hint:

Alcohol Formation via Alkene Hydration

• Alkenes react with H3O+ in aqueous acidic medium to form alcohols via Markovnikov addition.
• This is an efficient route to tertiary and secondary alcohols, depending on the substituents.
• Borane addition (Hydroboration) gives anti-Markovnikov alcohols.

Answer 1

The Correct Option is A

To prepare 1-ethylcyclohexanol, the most suitable route involves hydration of 1-ethylcyclohexene under acidic conditions. In this case:

• The alkene reacts with aqueous acid (${H_3O+}$) via electrophilic addition.
• This results in Markovnikov addition, where the OH group attaches to the more substituted carbon of the double bond.
• The product is 1-ethylcyclohexanol.

Other options either involve incorrect organometallic additions or cannot lead to the desired alcohol directly. \[ {CH_2=CH-C_6H_{11} + H_3O+ -> CH_3CH(OH)-C_6H_{11}} \]

Answer 2

Understanding the reaction:

The target compound is 1-ethylcyclohexanol, which is an alcohol with an ethyl group attached to the cyclohexane ring at the first carbon.

Step 1: Identify the starting material
The reactant \( CH_2=CH-C_6H_{11} \) is an alkene where the vinyl group (CH₂=CH-) is attached to the cyclohexyl ring. This structure corresponds to ethylcyclohexene.

Step 2: Understand the reaction type
When this alkene is treated with an acidic aqueous solution (\(H_3O^+\)), it undergoes acid-catalyzed hydration. The double bond breaks, and an -OH group adds to the more substituted carbon atom (Markovnikov’s rule), forming an alcohol.

Step 3: Write the product formed
The addition of water across the double bond gives \( CH_3CH(OH)-C_6H_{11} \), which is 1-ethylcyclohexanol.

Step 4: Final conclusion
Thus, the appropriate reactants for the preparation of 1-ethylcyclohexanol are:
\[ CH_2=CH-C_6H_{11} + H_3O^+ \longrightarrow CH_3CH(OH)-C_6H_{11} \]

Correct Answer: \( CH_2=CH-C_6H_{11} + H_3O^+ \to CH_3CH(OH)-C_6H_{11} \)