Question

Draw line structures of the following compounds and the product you would obtain from the reduction of each. (a) Isopropyl methyl ketone (b) \(p\) -Hydroxybenzaldehyde (c) 2 -Methylcyclopentanone

Short answer

(a) 2-Propanol, (b) p-Hydroxybenzyl alcohol, (c) 2-Methylcyclopentanol.

Step-by-step solution

Draw Isopropyl Methyl Ketone

Isopropyl methyl ketone can be drawn as a three-carbon chain with an isopropyl group on one end and a methyl group on the other, both connected to a ketone group (C=O) in the middle. The structure looks like:CH\(_3\)-CO-CH(CH\(_3\))\(_2\).

Reduce Isopropyl Methyl Ketone

The reduction of isopropyl methyl ketone typically involves converting the ketone (C=O) group into an alcohol (C-OH). This produces 2-propanol after reduction, which looks like:CH\(_3\)-CHOH-CH(CH\(_3\))\(_2\).

Draw p-Hydroxybenzaldehyde

p-Hydroxybenzaldehyde has a benzene ring with a hydroxyl group (OH) and an aldehyde group (CHO) at the para position. The structure is:C\(_6\)H\(_4\)(OH)CHO.

Reduce p-Hydroxybenzaldehyde

The reduction of an aldehyde group (CHO) turns it into a primary alcohol (CH\(_2\)OH). Therefore, p-hydroxybenzaldehyde becomes p-hydroxybenzyl alcohol:C\(_6\)H\(_4\)(OH)CH\(_2\)OH.

Draw 2-Methylcyclopentanone

2-Methylcyclopentanone is a cyclopentane ring with a ketone (C=O) group and a methyl group (CH\(_3\)) attached at the carbon adjacent to the ketone. The structure is:\[\begin{array}{c}C\(\_\)5H\(\_\)8O - \,\, (\text{Cyclopentane with }\, C=O \text{ at position 2})\end{array}\]

Reduce 2-Methylcyclopentanone

Reducing the ketone group on 2-methylcyclopentanone turns it into a secondary alcohol. The product is 2-methylcyclopentanol: Cyclopentane ring with OH group on the 2nd carbon.

Key concepts

Ketone Reduction

Ketones are organic compounds characterized by the presence of a carbonyl group (C=O) bonded to two alkyl groups. The process of reducing a ketone involves converting the carbonyl group into an alcohol group (C-OH). This transformation primarily uses reducing agents like sodium borohydride (\(\text{NaBH}_4\)) or lithium aluminum hydride (\(\text{LiAlH}_4\)). These agents donate hydride ions (\(\text{H}^-\)), essentially adding hydrogen atoms to the carbonyl carbon, reforming it into a hydroxyl group.

• One common example is the reduction of isopropyl methyl ketone. Through this reaction, its keto group is transformed into a secondary alcohol, yielding 2-propanol.


• Ketone reduction is crucial in organic synthesis, particularly in creating alcohols that may act as precursors for various complex molecules.

This process is valuable not only in the laboratory but in pharmaceuticals and other industries as well. Understanding the mechanistic pathway can play a vital role in designing synthetic routes for important chemical compounds.

Aldehyde Reduction

Aldehydes, similar to ketones, contain a carbonyl group (C=O) but with at least one hydrogen atom attached to the carbonyl carbon. The reduction of an aldehyde typically results in the conversion of the aldehyde group to a primary alcohol. This transformation also utilizes reducing agents such as sodium borohydride or lithium aluminum hydride, similar to the reduction of ketones.
This process is exemplified by the reduction of \(p\)-hydroxybenzaldehyde. The aldehyde in this compound is reduced to form \(p\)-hydroxybenzyl alcohol, maintaining the aromatic structure intact while converting the aldehyde group into a hydroxyl group at the para position (the opposite side) on the benzene ring.

• The conversion from an aldehyde to an alcohol is often used in synthesis due to the versatility of alcohols in further chemical transformations.


• Alcohols formed via reduction can undergo reactions like esterification or can be oxidized back to aldehydes if needed, showcasing their dynamic role in organic reactions.

Understanding this concept is fundamental to mastering organic synthetic strategies.

Alcohol Formation

Alcohols are pivotal in organic chemistry, functioning as intermediates and end products in numerous reactions due to their functional group's versatility. Forming alcohols through the reduction of carbonyl-containing compounds, such as ketones and aldehydes, is a widespread technique.
Alcohol formation from ketones generates secondary alcohols, while aldehydes yield primary alcohols. This difference is due to the varying structures of ketones and aldehydes. Secondary alcohols have the hydroxyl group attached to a carbon that is connected to two other carbon atoms. In contrast, primary alcohols have it attached to a carbon that is bonded to only one other carbon atom and two hydrogens.

• With 2-methylcyclopentanone, reduction leads to 2-methylcyclopentanol, a secondary alcohol with the hydroxyl at the position previously housing the carbonyl group.


• The importance of alcohol formation cannot be understated, as alcohols serve as solvents, antiseptics, fuels, and reagents in many industrial and laboratory applications.


• Furthermore, alcohols participate in dehydration and oxidation reactions, further emphasizing their centrality in chemistry.

Mastery of alcohol formation and the ability to predict the outcome of such reductions are essential skills in organic chemistry.