Carbonyl

Carbonyl is a functional group in organic chemistry characterized by a carbon atom double-bonded to an oxygen atom: C=O. It is a fundamental moiety in organic synthesis and is present in a wide variety of chemical compounds, ranging from simple aldehydes and ketones to more complex molecules like carboxylic acids, esters, and amides.

Structure and Bonding

The carbonyl group consists of a carbon atom and an oxygen atom connected by a double bond. This double bond is polar due to the difference in electronegativity between the carbon and the oxygen, making the oxygen partially negative and the carbon partially positive. This polarity affects the chemical reactivity of carbonyl compounds, making them susceptible to nucleophilic attack.

Properties

Carbonyl compounds are known for their diverse chemical properties. They can serve as electrophiles in nucleophilic addition or nucleophilic acyl substitution reactions due to the partial positive charge on the carbonyl carbon. The presence of the carbonyl group also significantly affects the boiling points and solubility of compounds. Generally, compounds containing a carbonyl group have higher boiling points than similar non-carbonyl compounds due to the possibility of hydrogen bonding with the oxygen.

Reactivity

The reactivity of the carbonyl group is largely influenced by its polar nature. In aldehydes and ketones, the carbonyl carbon is attacked by nucleophiles in a reaction mechanism known as nucleophilic addition. In carboxylic acid derivatives, such as esters and amides, the carbonyl carbon undergoes nucleophilic acyl substitution.

Synthesis

Carbonyl groups can be introduced into organic molecules by various methods. One common method is the oxidation of alcohols. Aldehydes are typically formed by the oxidation of primary alcohols, while ketones are produced from secondary alcohols. Other methods include the ozonolysis of alkenes, the Friedel-Crafts acylation of aromatic compounds, and the use of organometallic reagents.

Applications

Carbonyl compounds are ubiquitous in biochemistry, pharmaceuticals, and industrial chemistry. They are involved in numerous biochemical processes and are central to the structure of many important natural and synthetic molecules, including hormones, vitamins, and plastics.

See Also

• Aldehyde
• Ketone
• Carboxylic acid
• Ester
• Amide