Problem 2 What two peaks would you expect ... [FREE SOLUTION]

Chapter 11: Problem 2

What two peaks would you expect to see in the IR spectrum of a carboxylic acid?

Short Answer

Expert verified

The IR spectrum of a carboxylic acid shows peaks at 1700-1750 cm鈦宦� and 2500-3300 cm鈦宦�.

Step by step solution

Identify the Functional Groups

A carboxylic acid contains two key functional groups: a carbonyl group (C=O) and a hydroxyl group (O-H) attached to the same carbon atom.

Determine IR Absorption Range for Carbonyl Group

The carbonyl group (C=O) in a carboxylic acid typically absorbs infrared light in the range of 1700-1750 cm鈦宦�. This is a strong and sharp absorption peak.

Determine IR Absorption Range for Hydroxyl Group

The hydroxyl group (O-H) in a carboxylic acid shows a broad absorption band in the range of 2500-3300 cm鈦宦� due to hydrogen bonding.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Functional Groups Identification

Carboxylic acids are organic compounds. They feature a distinct functional group combination that defines their properties and reactivity.
The main functional groups in carboxylic acids are:

Carbonyl Group (C=O): This group includes a carbon atom double-bonded to an oxygen atom.
Hydroxyl Group (O-H): This group consists of an oxygen atom bonded to a hydrogen atom.

These functional groups are both bonded to the same carbon atom, forming the overall structure of a carboxylic acid: R-COOH (where R represents a hydrocarbon group or hydrogen atom). The IR spectrum of a carboxylic acid will showcase the characteristic absorption peaks of these functional groups, allowing them to be identified effectively.

Carbonyl Group Absorption

The carbonyl group in carboxylic acids has a strong and distinct absorption peak in the IR spectrum.
This peak appears due to the stretching vibration of the carbon-oxygen double bond (C=O).
The absorption range for the carbonyl group in carboxylic acids is typically:

1700-1750 cm^-1: This range indicates a strong and sharp peak characteristic of the carbonyl group.

This absorption is one of the most significant peaks observed in the IR spectrum. It helps in identifying the presence of carboxylic acids. By comparing this peak to known values, chemists can confirm the presence of the carbonyl group.

Hydroxyl Group Absorption

The hydroxyl group in carboxylic acids contributes another key absorption feature in the IR spectrum.
Unlike the carbonyl group, the hydroxyl group shows a much broader peak.
This is due to hydrogen bonding interactions, which spread out the absorption.
The typical absorption range for the hydroxyl group in carboxylic acids is:

2500-3300 cm^-1: This broad absorption band is due to the stretching vibration of the O-H bond.

This region of the IR spectrum is distinctive for the hydroxyl group. It helps in confirming the presence of carboxylic acids. The broad and strong nature of this peak distinguishes it from other hydroxyl-containing compounds not involved in hydrogen bonding.

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91影视

What two peaks would you expect to see in the IR spectrum of a carboxylic acid?

Short Answer

Step by step solution

Identify the Functional Groups

Determine IR Absorption Range for Carbonyl Group

Determine IR Absorption Range for Hydroxyl Group

Key Concepts

Functional Groups Identification

Carbonyl Group Absorption

Hydroxyl Group Absorption

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