Carbonyl Carbon

Definition

The carbonyl carbon is the central carbon atom in a carbonyl group, which is a functional group consisting of a carbon atom double-bonded to an oxygen atom. This carbonyl carbon is a key structural feature in various organic compounds, including aldehydes, ketones, carboxylic acids, and their derivatives, and plays a crucial role in the reactivity and properties of these compounds.

5 Must Know Facts For Your Next Test

1. The carbonyl carbon is partially positively charged due to the high electronegativity of the oxygen atom, making it susceptible to nucleophilic attack.
2. In the reduction of carbonyl compounds to alcohols (Section 17.4), the carbonyl carbon is reduced to a secondary or primary alcohol carbon.
3. In the nucleophilic addition of amines to carbonyl compounds (Section 19.8), the carbonyl carbon is attacked by the nucleophilic amine, forming an imine or enamine intermediate.
4. The carbonyl carbon exhibits characteristic absorption in the infrared (IR) spectrum, which can be used to identify the presence of carbonyl groups (Section 19.14).
5. Reactions of carboxylic acids (Section 20.6) often involve the carbonyl carbon, such as in the formation of esters, amides, and acyl halides.

Review Questions

• Explain the role of the carbonyl carbon in the reduction of carbonyl compounds to alcohols.
  • In the reduction of carbonyl compounds to alcohols (Section 17.4), the carbonyl carbon is the site of the reduction reaction. The carbonyl carbon, which is partially positively charged due to the high electronegativity of the oxygen atom, is attacked by a reducing agent, such as hydrogen gas or a hydride reagent. This results in the formation of a new covalent bond between the carbonyl carbon and the hydrogen or hydride, reducing the carbonyl group to a secondary or primary alcohol group.
• Describe the role of the carbonyl carbon in the nucleophilic addition of amines to form imines and enamines.
  • In the nucleophilic addition of amines to carbonyl compounds (Section 19.8), the carbonyl carbon is the electrophilic site that is attacked by the nucleophilic amine. The partially positively charged carbonyl carbon is susceptible to nucleophilic attack, and the amine adds to the carbonyl carbon, forming a tetrahedral intermediate. This intermediate then undergoes dehydration, resulting in the formation of an imine or enamine, where the carbonyl carbon is now part of a C=N double bond.
• Analyze the importance of the carbonyl carbon in the spectroscopic identification of aldehydes and ketones.
  • The carbonyl carbon in aldehydes and ketones exhibits a characteristic absorption in the infrared (IR) spectrum (Section 19.14). This absorption, typically in the range of 1700-1750 cm$^{-1}$, is due to the C=O stretching vibration of the carbonyl group. The presence and position of this absorption can be used to identify the presence of carbonyl groups in organic compounds, which is crucial for the structural elucidation of aldehydes, ketones, and other carbonyl-containing molecules.

Related terms

Carbonyl Group: A functional group consisting of a carbon atom double-bonded to an oxygen atom, represented as C=O.

Nucleophilic Addition: A reaction in which a nucleophile (electron-rich species) attacks the carbonyl carbon of a carbonyl compound, forming a new covalent bond.

Electrophilic Addition: A reaction in which an electrophile (electron-deficient species) adds to the carbonyl carbon of a carbonyl compound, forming a new covalent bond.