Which functional groups correspond to the main characteristic peaks of the infrared spectrum (IR) of acetone?

Which functional groups correspond to the main characteristic peaks of the infrared spectrum (IR) of acetone?

Infrared spectroscopy (IR) is a commonly used analytical technique that can identify the structure of a compound by the characteristic vibrational absorption peaks of the functional groups in the molecule. As a common organic compound, there are many characteristic peaks in the infrared spectrum of acetone, which correspond to different functional groups. In this paper, the main characteristic peaks of the infrared spectrum of acetone and their corresponding functional groups are analyzed in detail.

1. Overview of Molecular Structure and Infrared Spectrum of Acetone

acetone (chemical formula CHY3 COCH3) is a compound containing a carbonyl group (C = O), and its molecular structure also includes two methyl groups (CHY2) and a methylene group (CH2). In the infrared spectrum analysis, the molecular vibration mode of acetone is closely related to its functional groups, especially the strong absorption peak of carbonyl group is an important feature in the IR spectrum of acetone.

2. Absorption peaks of hydroxyl (O-H) and carbonyl (C = O)

in the infrared spectrum of acetone, the most significant characteristic peak is the stretching vibration absorption peak of carbonyl group (C = O). Typically, the absorption peak for C = O is located around 1700cm. Because the electronic environment of carbonyl in acetone molecule is relatively stable, the absorption peak of C = O is usually a sharp peak with high intensity, which makes it one of the most characteristic peaks in acetone molecule.

Acetone does not contain hydroxyl (O-H) functional groups in the molecule, so O-H absorption peaks usually do not appear in the IR spectrum of acetone. If a O-H absorption peak is observed in the experiment, it may be due to the incorporation of moisture or other hydroxyl-containing compounds in the sample.

3. Absorption peaks of methyl (CH1) and methylene (CH2)

in addition to the absorption peak of the carbonyl group, the methyl and methylene groups in the acetone molecule also produce characteristic vibrational absorption peaks. Specifically:

• asymmetric stretching vibration of C- H: In the IR spectrum of acetone, the asymmetric stretching vibration of the C- H usually appears around 2820cm. ¹.
• Symmetrical stretching vibration of C- H: The symmetrical telescopic vibration of the C- H usually appears around 2720cm. ¹.
• Bending vibration of C- H: The bending vibration of the C- H usually appears around 1450cm. ¹.

These peaks correspond to the characteristic vibrations of the C- H bonds of the methyl and methylene groups in the acetone molecule, respectively.

4. Analysis of other characteristic peaks

in addition to the above peaks, some other characteristic peaks may be observed in the IR spectrum of acetone, such:

• bending vibration of C = O: In the acetone molecule, the bending vibration of the C = O bond usually appears around 670 cm¹.
• C- telescopic vibration of C: The telescopic vibration of the C- C key usually appears around 1050cm. ¹.

The existence of these peaks further confirms the type and structure of the functional groups in the acetone molecule.

5. Influence factors of peak position and intensity

the position and intensity of the characteristic peaks in the IR spectrum of acetone are affected by many factors, such:

• solvent type of solution: Different solvents may affect the polarization effect of acetone molecules, resulting in a slight shift in the position of the C = O absorption peak.
• Purity of the sample: If other substances are mixed in the sample, additional absorption peaks may be introduced, which may interfere with the analysis of the characteristic peaks of acetone.
• experimental conditions: The test conditions of IR spectrum (such as scanning range, resolution, etc.) will also affect the observation effect of characteristic peaks.

6. Summary and Application

by analyzing the characteristic peaks in the infrared spectrum of acetone, we can clearly identify the vibrational absorption peaks corresponding to its functional groups. In particular, the sharp peak of the absorption peak of C = O in the vicinity of 1700cm is one of the important signs of acetone molecule. The absorption peak of C- H bond and the bending vibration peak of C = C bond also provide strong support for the structural characterization of acetone.

Infrared spectrum analysis is not only an important means to identify the molecular structure of acetone, but also plays an important role in chemical synthesis, quality control and other fields. Through the in-depth study of the infrared spectrum of acetone, the molecular characteristics and the interaction of functional groups can be better understood.