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

MIBK (Methyl Isobutyl Ketone, chemical formula C≡H≡O) is a commonly used organic compound that is widely used in industrial production and laboratories. Because of its many functional groups, infrared spectroscopy (IR) analysis is one of the important means to study and identify the chemical structure of MIBK. In this paper, the infrared spectrum characteristic peaks of MIBK and their corresponding functional groups will be analyzed in detail.

1. What is infrared spectroscopy (IR) analysis?

Infrared spectroscopy is a spectroscopic technique based on the absorption of infrared radiation by molecules, which is used to detect and analyze the molecular structure of substances. Each functional group has its own unique vibration frequency, these frequencies will appear as a specific absorption peak in the infrared spectrum. By analyzing the position, intensity and shape of these absorption peaks, it is possible to infer the functional groups that may be present in the substance.

MIBK is a compound containing multiple functional groups, and its infrared spectrum will show multiple characteristic peaks. The positions of these characteristic peaks are closely related to their molecular structure.

2. The chemical structure and main functional groups of MIBK

the chemical structure of MIBK can be expressed: CH₃-C(O)-C(H)(CH₂CH₃)₂

from the structural point of view, MIBK mainly contains the following functional groups:

1. carbonyl (C = O): is located in the ketone group and is the core functional group of MIBK.
2. Ether bond (C-O): Due to the existence of methoxy similar structure in the structure of MIBK, it may show C- O characteristic peaks.
3. Methyl (CH3) and ethyl (CH₂ CH3) these are common alkyl functional groups in MIBK molecules.

3. MIBK infrared spectrum characteristic peak analysis

each peak in the infrared spectrum corresponds to the vibration of a certain functional group in the molecule. The following are the main IR characteristic peaks of MIBK and their corresponding functional groups:

(1)C = O (carbonyl) characteristic peak

the carbonyl group (C = O) in MIBK molecule is one of the most prominent functional groups in its structure. In the infrared spectrum, the stretching vibration of C = O usually occurs in the region of 1700 cm¹ to 1750 cm¹.

• The position of the peak: The C = O peak of MIBK is usually located about 1715 cm¹ nearby.
• Intensity of peak: The intensity of this peak is higher, indicating the presence of the C = O group.
• The shape of the peak: The peak shape is symmetrical and usually shows a slight asymmetric expansion vibration.

(2) The characteristic peak of C- O (ether bond or carbon-oxygen bond)

although there is no traditional ether bond in the structure of MIBK, the vibration of the carbon-oxygen bond in the molecule is still reflected in the infrared spectrum. The expansion and contraction vibration of C- O usually occurs in the region of 1000 cm¹ to 1250 cm¹.

• The position of the peak: The C- O peak of MIBK is usually located approximately 1050 cm¹ to 1150 cm¹ between.
• Intensity of peak: The intensity of this peak is moderate, indicating the presence of C- O bonds.
• Meaning of Peak: The existence of C- O peak indicates the existence of a carbon-oxygen bond connected to the carbonyl group in the MIBK molecule, which is closely related to the properties of its ketones.

(3) The characteristic peaks of methyl (CHFL3) and ethyl (CH₂ CHFL3)

the MIBK molecule also contains multiple methyl and ethyl functional groups. The vibrations of these alkyl functional groups usually appear in the infrared spectrum as characteristic peaks of the fingerprint region, I .e., the region between 800 cm¹ and 1500 cm≡¹.

• The characteristic peak of methyl (CHL3) symmetrical and asymmetrical telescopic vibrations of: CH3 usually appear in 2800 cm¹ to 3000 cm¹ and 1450 cm¹ to 1500 cm¹ between.
• The characteristic peak of ethyl (CH₂ CH3): CH₂ and CHL3 vibrations usually appear in 2800 cm¹ to 3000 cm¹ and 1350 cm¹ to 1500 cm¹ between.

(4)O-H (hydroxyl) characteristic peak

it should be noted that MIBK does not contain hydroxyl (-OH) functional groups in the molecule. However, in the actual analysis, if the sample is contaminated or moisture is present, the absorption peak of the hydroxyl group may appear (usually between 3200cm and 3600cm). Therefore, when analyzing the infrared spectrum of MIBK, it is necessary to exclude external interference.

4. Factors Affecting Infrared Spectrum Analysis

in actual analysis, the infrared spectrum of MIBK may be affected by many factors, including sample preparation method, test conditions (such as sample thickness, scanning times, resolution, etc.) and external environment (such as temperature, humidity). Therefore, the control of experimental conditions and the purity of the sample are very important when performing infrared spectroscopy.

The molecular structure of MIBK may lead to changes in the intensity of some characteristic peaks. For example, the absorption peak of a carbonyl group (C = O) may be blue-shifted or red-shifted by changes in the electronic environment of the molecule.

5. Summary

the infrared spectrum characteristic peaks of MIBK are closely related to the functional groups in its molecular structure. By analyzing the infrared spectrum, the existence of functional groups such as C═O, C- O, CHFL3 and CH₂ CH3 can be clearly identified. These characteristic peaks not only help to confirm the chemical structure of MIBK, but also provide important reference materials for its quality control and application research.

In practical applications, infrared spectroscopy is a fast, accurate and non-destructive detection method, which is widely used in chemical, pharmaceutical, food and environmental monitoring and other fields. For MIBK, an important organic compound, infrared spectroscopy can help researchers better understand its molecular properties and provide support for its practical applications.