Question

An organic compound with the molecular formula \(\mathrm{C}_{3} \mathrm{H}_{10} \mathrm{O}\) forms \(2.4\) -DNP derivative, reduces Tollens" reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives \(1.2\) -benzenedicarboxylic acid. Identify the compound.

Short answer

The compound is phenylmethanol (benzyl alcohol).

Step-by-step solution

Analyze the Reactions and Functional Groups

The compound forms a 2,4-DNP derivative and reduces Tollens' reagent, which indicates the presence of an aldehyde group. The Cannizzaro reaction further supports this, as it involves aldehydes without alpha hydrogen atoms.

Deduce the Structure from Oxidation Products

During vigorous oxidation, the compound forms 1,2-benzenedicarboxylic acid. This indicates that the original compound must have been a benzaldehyde derivative with a structure related to benzene.

Construct the Compound Structure

Given the molecular formula \(\mathrm{C}_{3}\mathrm{H}_{10}\mathrm{O}\), and combining it with the step-wise deductions, the compound can be determined to be phenylmethanol (Benzyl alcohol, \(\mathrm{C}_6\mathrm{H}_5\mathrm{CH}_2\mathrm{OH}\)), which fits all criteria: reduction by Tollens, forming a 2,4-DNP derivative, undergoing a Cannizzaro reaction, and oxidizing to phthalic acid (1,2-benzenedicarboxylic acid).

Key concepts

Aldehyde Reactions

In organic chemistry, aldehyde reactions are pivotal in identifying and converting various aldehyde functionalities. An aldehyde group is characterized by the presence of a carbonyl group, where the carbon is connected to a hydrogen and possibly other carbon atoms. This configuration makes aldehydes highly reactive and versatile in different chemical reactions.

Aldehydes readily form 2,4-DNP (dinitrophenylhydrazine) derivatives, which is a classical test for the presence of carbonyl groups. When a compound reacts with 2,4-DNP, it signifies a carbonyl group, typically from either aldehydes or ketones. The compound's formation of a 2,4-DNP derivative indicates that it contains an aldehyde or ketone group.

Additionally, aldehydes can reduce Tollens' reagent, which is a solution of silver nitrate in ammonia. When an aldehyde reduces this reagent, a silver mirror forms, demonstrating the presence of aldehydes. These reactions are important basic tests in organic chemistry for functional group identification.

Cannizzaro Reaction

The Cannizzaro reaction is unique to aldehydes without an alpha hydrogen atom. In this reaction, a specific type of dismutation takes place. One aldehyde molecule is oxidized to a carboxylic acid, while another is reduced to an alcohol.

Key characteristics of the Cannizzaro reaction include:

• It involves aldehydes that lack an alpha hydrogen. Such aldehydes cannot undergo standard enolization and subsequently aldol reactions.
• The reaction is self-redox, meaning one molecule donates electrons while another receives electrons.

This reaction is indicative of particular aldehydes, helping to narrow down possible structures when identifying unknown organic compounds.

Oxidation Reactions

Oxidation reactions play a crucial role in the transformation of organic compounds, especially when identifying structures through their oxidative products. These reactions involve the increase of oxidation state, typically by the addition of oxygen or removal of hydrogen.

In the context of the mystery compound, vigorous oxidation leading to the formation of 1,2-benzenedicarboxylic acid indicates the presence of an aromatic ring, specifically a benzene derivative such as benzyl alcohol.

Oxidation helps to further identify functional groups by converting them to more recognizable oxygenated compounds. Through processes like oxidation, chemists can deduce the original structure of compounds, as seen in identifying the precursor to phthalic acid. Understanding oxidation reactions opens paths to creating a wide variety of valuable organic compounds.