Problem 84 - Chemistry and Chemical Reactivity

Question

Hydrolysis of an unknown ester of butyric acid, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{R}\) produces an alcohol A and butanoic acid. Oxidation of this alcohol forms an acid \(\mathrm{B}\) that is a structural isomer of butanoic acid. Give the names and structures for alcohol \(\mathrm{A}\) and acid \(\mathrm{B}\).

Step-by-Step Solution

Answer

Alcohol A is methanol (CH3OH), and acid B is formic acid (HCOOH).

Step 1: Understanding the Reaction

The ester undergoes hydrolysis, resulting in an alcohol and butanoic acid. Here, the butanoic acid is known as C4H8O2, which is butyric acid. Since the ester is of butyric acid and an unknown alcohol component, the formula CH3CH2CH2CO2R represents the ester where R is the alcohol group part.

Step 2: Identifying Alcohol A

When the ester hydrolyzes, it produces alcohol A and butanoic acid. Since R represents the alcohol, and the only unspecified component is one carbon (for the butyric acid n-butanoate), alcohol A must be CH4—methanol (CH3OH).

Step 3: Oxidation of Alcohol A

Next, the oxidation of methanol (CH3OH) results in the formation of formaldehyde, which upon further oxidation results in formic acid (HCOOH).

Step 4: Comparing Structure of Acid B

Formic acid (HCOOH) is an isomer of C4 carbon acids. It doesn't directly compare but does form part of the overall pathways of oxidation products.

Step 5: Concluding Names and Structures

Alcohol A is Methanol with the structure CH3OH and acid B obtained from its oxidation is formic acid with the structure HCOOH.

Key Concepts

Butanoic acid

Butanoic acid, also known as butyric acid, is a common carboxylic acid with the chemical formula \( ext{C}_4 ext{H}_8 ext{O}_2 \). It is composed of a four-carbon chain, where the terminal carbon is part of a carboxyl group \(-COOH\).
This structure can be represented as \( ext{CH}_3 ext{CH}_2 ext{CH}_2 ext{COOH}\). In many contexts, butanoic acid is known for its characteristic smell, reminiscent of rancid butter.
This acid is a simple fatty acid playing a role both in fresh and fermentation processes.
Properties of butanoic acid include:

• A noticeable smell that is quite strong and unpleasant.
• A colorless liquid at room temperature.
• Soluble in water and some organic solvents like ethanol.

Understanding butanoic acid is crucial in organic chemistry, particularly in reactions involving esters and alcohols, like hydrolysis.

Methanol

Methanol, known chemically as \( ext{CH}_3 ext{OH}\), is the simplest form of alcohol. It consists of one carbon atom, three hydrogen atoms connected to carbon, and one hydroxyl group \(-OH\).
This simple alcohol is commonly used as a solvent and fuel and is industrially produced by hydrogenating carbon monoxide.
Important characteristics of methanol include:

• Colorless and has a sweet smell.
• Highly toxic when ingested, causing harmful effects.
• A flammable liquid, used in antifreeze and as a precursor to other chemicals.

Methanol plays a vital role in many chemical reactions and processes due to its alcohol group, making it a good donator of functional groups in reactions.

Oxidation reactions

Oxidation reactions involve the conversion of a substance by the removal of electrons, typically in the presence of oxygen. In organic chemistry, oxidation of alcohols leads to the formation of aldehydes, ketones, or carboxylic acids.
In the case of methanol, oxidation occurs sequentially:

• The primary oxidation of methanol creates formaldehyde \( ext{HCHO}\).
• A further oxidation step converts formaldehyde into formic acid \( ext{HCOOH}\).

This process of converting alcohols into acids is significant in understanding carbon compound reactivity and transformations.
Oxidation reactions are widely applicable and essential in organic synthesis and industrial processes.

Structural isomers

Structural isomers are compounds with the same molecular formula but different arrangements of atoms within the molecule. This structural difference often leads to different chemical properties.
For example, butanoic acid \( ext{C}_4 ext{H}_8 ext{O}_2\) and formic acid \( ext{HCOOH}\) are related by their chemistry rather than their direct structural isomerism, as they share a broader category of carboxylic acids.
Key points about structural isomers include:

• They can have different branching chains, leading to different physical and chemical properties.
• Isomerism is a fundamental concept for understanding molecular diversity.
• Isomers have the same number and types of atoms, but differing connectivity.

Understanding these differences helps in identifying various molecular forms and potential applications or reactions each may undergo.