Skip to main content
Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 14 - Structural Identification I: Infrared Spectroscopy and Mass SpectrometryProblem 51
Chapter 13, Problem 51

A carboxylic acid can be converted to an ester using the conditions shown. Explain how a comparison of an IR spectrum of the reactant(s) and product can be used to determine whether the reaction was successful or not.
Chemical reaction: carboxylic acid and alcohol form an ester and water, using H2SO4 as a catalyst.

Verified step by step guidance
1
Identify the functional groups present in the reactant (carboxylic acid) and the product (ester). Carboxylic acids have a characteristic C=O stretch around 1700 cm-1 and an O-H stretch around 2500-3300 cm-1 in their IR spectrum.
Recognize that esters have a C=O stretch similar to carboxylic acids, but they lack the broad O-H stretch. Instead, esters show a C-O stretch typically in the range of 1050-1300 cm-1.
Compare the IR spectrum of the reactant with that of the product. Look for the disappearance of the broad O-H stretch in the product's spectrum, which indicates the loss of the carboxylic acid's hydroxyl group.
Check for the presence of the ester C-O stretch in the product's IR spectrum, which should appear as a new peak compared to the reactant's spectrum.
Conclude that the reaction was successful if the IR spectrum of the product shows the disappearance of the O-H stretch and the appearance of the C-O stretch, confirming the conversion of the carboxylic acid to an ester.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Carboxylic Acid to Ester Conversion

The conversion of a carboxylic acid to an ester typically involves a reaction with an alcohol in the presence of an acid catalyst, known as esterification. This process replaces the hydroxyl group (-OH) of the carboxylic acid with an alkoxy group (-OR) from the alcohol, forming an ester and water as byproducts.
Recommended video:
Guided course
03:50
Intro to Carboxylic Acid Derivatives

Infrared (IR) Spectroscopy

IR spectroscopy is a technique used to identify functional groups in organic compounds by measuring the absorption of infrared light. Different functional groups absorb specific frequencies, creating a spectrum that can be analyzed to determine the presence or absence of particular bonds, such as the carbonyl group in carboxylic acids and esters.
Recommended video:
Guided course
16:04
General Features of IR Spect

Functional Group Identification via IR Spectrum

In the IR spectrum, carboxylic acids show a broad O-H stretch around 2500-3000 cm⁻¹ and a sharp C=O stretch near 1700 cm⁻¹. Esters, however, lack the O-H stretch and exhibit a C=O stretch around 1735-1750 cm⁻¹. Comparing these spectra allows one to confirm the conversion by the disappearance of the O-H stretch and the shift in the C=O stretch.
Recommended video:
Guided course
04:04
Drawing Concealed Functional Groups
Related Practice
Textbook Question

Would you expect the stretching band of the carbonyl to appear at a higher frequency for cyclohexanecarbaldehyde or benzaldehyde? Explain.

1017
views
Textbook Question

Identify the important bands you would expect to find in an IR spectrum for the following molecules.

(a)

1004
views
Textbook Question

Identify the important bands you would expect to find in an IR spectrum for the following molecules.

(c)

995
views
Textbook Question

What functional groups might be present in the IR spectra for the molecules with the given molecular formulas. [Be sure to use the molecular formula in your analysis.]

(b) C₃H₄O₄

<IMAGE>

1283
views
Textbook Question

Under acidic conditions, alkene A can be isomerized to the more stable alkene B. How could IR spectroscopy be used to distinguish between A and B? [There are a few correct answers.]

945
views
Textbook Question

Hoping to make the following diene, a chemist treated the diol shown with acid. Based on the IR spectrum, was the reaction successful? If not, what compound was made instead?

<IMAGE>

1015
views