Predict the products of the following reactions.
(e)
(f)

Verified step by step guidance

1. Step 1: Analyze the first reaction. The starting material is an ester (Ph-C(O)-OCH2CH3), and the reagents are lithium aluminum hydride (LiAlH4) followed by water (H2O). LiAlH4 is a strong reducing agent that reduces esters to primary alcohols. The ester bond will be cleaved, and the carbonyl group will be reduced to an alcohol.
2. Step 2: Predict the product for the first reaction. The phenyl group (Ph) remains attached to the carbon, and the ethoxy group (-OCH2CH3) is replaced by a hydroxyl group (-OH). This results in the formation of benzyl alcohol (Ph-CH2OH).
3. Step 3: Analyze the second reaction. The starting material is a lactam (cyclic amide), and the reagents are LiAlH4 followed by H2O. LiAlH4 reduces amides to amines by breaking the C=O bond and converting the carbonyl group into a CH2 group.
4. Step 4: Predict the product for the second reaction. The cyclic structure remains intact, but the carbonyl group is reduced to a CH2 group, resulting in a cyclic amine. The product is a six-membered ring with a secondary amine (-NH) and a CH2 group replacing the carbonyl.
5. Step 5: Summarize the reaction outcomes. For reaction (e), the ester is reduced to benzyl alcohol. For reaction (f), the lactam is reduced to a cyclic amine. Both reactions involve the use of LiAlH4 as a reducing agent followed by hydrolysis with water.

Key Concepts

Reduction Reactions

Reduction reactions involve the gain of electrons or the decrease in oxidation state of a molecule. In organic chemistry, this often refers to the conversion of carbonyl compounds (like aldehydes and ketones) to alcohols. Lithium aluminum hydride (LiAlH4) is a strong reducing agent commonly used to reduce carbonyl groups, resulting in the formation of alcohols.

Lithium Aluminum Hydride (LiAlH4)

Lithium aluminum hydride is a powerful reducing agent used in organic synthesis. It can reduce a variety of functional groups, including esters, carboxylic acids, and carbonyls, to their corresponding alcohols. Due to its reactivity, it must be handled under anhydrous conditions and is typically followed by a workup step involving water to quench excess reagent and convert the alkoxide intermediate to an alcohol.

Mechanism of Reduction

The mechanism of reduction with LiAlH4 involves nucleophilic attack by the hydride ion (H-) on the electrophilic carbon of the carbonyl group. This forms a tetrahedral intermediate, which can then collapse to yield an alcohol after protonation. Understanding this mechanism is crucial for predicting the products of reactions involving carbonyl compounds and reducing agents.