Question

In order to achieve the following conversion, O=C(C=CC1CCCCC1)OCC1CCC(C=CCO)CC1 which of the following reducing agents should be employed? (A) \(\mathrm{NaBH}_{4}\) (B) \(\mathrm{H}_{2}, \mathrm{Ni}\) (C) \(\mathrm{LiAlH}_{4}\) (D) $\left[\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHO}\right]_{3} \mathrm{Al},\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHOH}$

Short answer

The best reagent to achieve the desired conversion is (C) \(\mathrm{LiAlH}_{4}\), as it selectively reduces the ester functional group to the corresponding alcohol without affecting the alkene group.

Step-by-step solution

Identify the molecule and its functional groups

The given SMILES notation is O=C(C=CC1CCCCC1)OCC1CCC(C=CCO)CC1. We can draw the molecule from it and find that there are two functional groups present in the molecule: an ester (O=C(C=CC1CCCCC1)OCC1CCC(C=CCO)CC1) and an alkene group (C=C) present in the carbon chain.

Analyze the reactivity of functional groups with the given reagents

We need to check how each of the given reagents interacts with ester and alkene functional groups: (A) \(\mathrm{NaBH}_{4}\): Sodium borohydride is a selective reducing agent, which primarily reduces aldehydes and ketones to their respective alcohols. It doesn't react with esters or alkenes. (B) \(\mathrm{H}_{2}, \mathrm{Ni}\): Hydrogen gas with a nickel catalyst is widely used in the hydrogenation of alkenes to alkanes. It has limited reactivity with esters. (C) \(\mathrm{LiAlH}_{4}\): Lithium aluminum hydride is a powerful reducing agent and is capable of reducing almost all carbonyl-containing functional groups, including esters, to alcohols. It also doesn't react with alkenes. (D) \(\left[\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHO}\right]_{3} \mathrm{Al},\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHOH}\): Aluminum isopropoxide with isopropanol is a weak reducing agent, often used in reduction of esters to the corresponding alcohols. However, it is not suitable for this case, as there are more reactive and selective reagents available.

Choose the best reducing agent

Considering all the aforementioned reactions, the best reagent to convert the given molecule is (C) \(\mathrm{LiAlH}_{4}\), as it will selectively reduce the ester functional group to the corresponding alcohol without affecting the alkene group.