2-pentanone

Definition

2-pentanone is a simple ketone compound with the chemical formula CH3C(O)CH2CH3. It is a colorless, volatile liquid with a sweet, fruity odor and is commonly used as a solvent and in the production of other chemicals.

5 Must Know Facts For Your Next Test

1. The IUPAC name for 2-pentanone is derived from the parent alkane 'pentane' and the ketone functional group, indicating the position of the carbonyl group on the 2nd carbon.
2. The carbonyl carbon in 2-pentanone is sp2 hybridized, giving it a planar geometry and allowing for resonance stabilization of the C=O bond.
3. In 1H NMR spectroscopy, 2-pentanone exhibits a characteristic singlet signal for the three equivalent methyl protons adjacent to the carbonyl group.
4. The strong carbonyl absorption band in the infrared spectrum of 2-pentanone appears around 1715-1730 cm^(-1), which is diagnostic for ketone functional groups.
5. 2-pentanone is a useful precursor in organic synthesis, particularly in the preparation of other ketones and alcohols through reactions like oxidation and reduction.

Review Questions

• Explain how the IUPAC naming system is used to identify the structure of 2-pentanone.
  • The IUPAC name '2-pentanone' indicates that the compound is a ketone (with the 'one' suffix) derived from the parent alkane 'pentane'. The '2-' prefix specifies that the carbonyl group is located on the second carbon of the five-carbon chain. This systematic naming approach allows for the unambiguous identification of the molecular structure and the position of the functional group.
• Describe the key features of the infrared (IR) spectrum that would be used to identify 2-pentanone.
  • The IR spectrum of 2-pentanone would exhibit a strong, characteristic absorption band around 1715-1730 cm^(-1) corresponding to the stretching vibration of the carbonyl (C=O) functional group. This absorption is diagnostic for ketone compounds and would be a crucial piece of evidence in identifying the presence of the carbonyl group in the structure of 2-pentanone. Additionally, the IR spectrum would provide information about other structural features, such as the presence of alkyl groups, that could further confirm the identity of the compound.
• Analyze how the $^1$H NMR spectrum of 2-pentanone can be used to elucidate its molecular structure.
  • The $^1$H NMR spectrum of 2-pentanone would show a characteristic singlet signal for the three equivalent methyl protons (CH$_3$) adjacent to the carbonyl group. This singlet, integrating for 3 protons, would be a key piece of evidence indicating the presence of a methyl group directly attached to the ketone functional group. Additionally, the spectrum would display signals corresponding to the other methylene and methine protons in the five-carbon chain, allowing for the complete structural elucidation of 2-pentanone based on the observed $^1$H NMR signals and their integration patterns.

Related terms

Ketone: A functional group consisting of a carbonyl (C=O) group bonded to two alkyl or aryl groups.

Nomenclature: The systematic naming of organic compounds based on established rules and conventions.

Infrared Spectroscopy: A technique used to identify functional groups and structural features of organic compounds by analyzing their absorption of infrared radiation.