Carbonyl Compounds
Carbonyl Compounds are the organic compounds containing carbon-oxygen double bond
(>C=0). >C=O is the most important functional group of organic chemistry.
Carbonyl compounds in which carbonyl group is bonded to a carbon and hydrogen are
known as aldehydes.
Carbonyl compounds in which carbonyl group is bonded to carbon atoms are known as
ketons.
The carbonyl compounds in which carbonyl group is bonded to oxygen are known
as carboxylic acids, and their derivatives (e.g. esters, anhydrides)
Carbonyl compounds where carbon is attached to nitrogen are called amides.
Carbonyl compounds where carbon is attached to haligen are called acyl halides.
In short, carbonyl compounds can be divided into two major groups
Aldehydes & Ketones
Carboxylic Acid & Its derivatives
Structure of Carbonyl Group
Carbonyl carbon is joined to three other atoms by s bonds; since these bonds utilize
sp2 orbitals, they lie in a plane, and are 120° apart. The remaining p-orbitals of carbon
overlaps a p-orbital of oxygen to form a p bond; carbon and oxygen are thus joined by a
double bond. The part of the molecule immediately surrounding carbonyl carbon lies in a
plane.
The electrons of a carbonyl double bond hold together atoms of quite different
electronegativity and hence the electrons are not equally shared; in particular the polar p-
cloud is pulled strongly towards the more electronegative atom, oxygen.
The carbonyl group, C = O, governs the chemistry of aldehydes and ketones. It does this in
two ways: a) By providing a site for nucleophilic addition, and
b) By increasing the acidity of hydrogen atoms attached to the alpha carbon.
Physical properties of carbonyl compounds
1. The boiling point of carbonyl compounds is higher than the alkanes with similar molecular
weight.
, 2. The boiling point increases with increasing number of carbon atom. This is because there are
more electrons, hence more temporary dipoles can be set up. More energy is required to
overcome these forces.
3. Besides temporary dipoles, permanent dipole-dipole forces are also present due to carbonyl
compounds being polar
4. Methanal and ethanal are gases at room temperature, while others are liquids
Carbonyl compounds are soluble in This is because they are able to form hydrogen bond with
water molecules.
The solubility decreases with increasing number of carbon atoms. This is because the long
hydrocarbon chain disrupts the hydrogen bonding.
Preparation of Aldehyde and Ketone
Aldehydes, synthesis:
• Oxidation of 1o alcohols
• Oxidation of methylaromatics
• Reduction of acid chlorides
Ketones, synthesis:
• Oxidation of 2o alcohols
• Friedel-Crafts acylation
• Coupling of R2CuLi with acid chloride
1- Oxidation of alcohols
CrO 3/ pyridine O
RCH 2 OH R
Cu / heat H
O
CrO 3/ pyridine
R2CH OH R C R
Cu / heat
Carbonyl Compounds are the organic compounds containing carbon-oxygen double bond
(>C=0). >C=O is the most important functional group of organic chemistry.
Carbonyl compounds in which carbonyl group is bonded to a carbon and hydrogen are
known as aldehydes.
Carbonyl compounds in which carbonyl group is bonded to carbon atoms are known as
ketons.
The carbonyl compounds in which carbonyl group is bonded to oxygen are known
as carboxylic acids, and their derivatives (e.g. esters, anhydrides)
Carbonyl compounds where carbon is attached to nitrogen are called amides.
Carbonyl compounds where carbon is attached to haligen are called acyl halides.
In short, carbonyl compounds can be divided into two major groups
Aldehydes & Ketones
Carboxylic Acid & Its derivatives
Structure of Carbonyl Group
Carbonyl carbon is joined to three other atoms by s bonds; since these bonds utilize
sp2 orbitals, they lie in a plane, and are 120° apart. The remaining p-orbitals of carbon
overlaps a p-orbital of oxygen to form a p bond; carbon and oxygen are thus joined by a
double bond. The part of the molecule immediately surrounding carbonyl carbon lies in a
plane.
The electrons of a carbonyl double bond hold together atoms of quite different
electronegativity and hence the electrons are not equally shared; in particular the polar p-
cloud is pulled strongly towards the more electronegative atom, oxygen.
The carbonyl group, C = O, governs the chemistry of aldehydes and ketones. It does this in
two ways: a) By providing a site for nucleophilic addition, and
b) By increasing the acidity of hydrogen atoms attached to the alpha carbon.
Physical properties of carbonyl compounds
1. The boiling point of carbonyl compounds is higher than the alkanes with similar molecular
weight.
, 2. The boiling point increases with increasing number of carbon atom. This is because there are
more electrons, hence more temporary dipoles can be set up. More energy is required to
overcome these forces.
3. Besides temporary dipoles, permanent dipole-dipole forces are also present due to carbonyl
compounds being polar
4. Methanal and ethanal are gases at room temperature, while others are liquids
Carbonyl compounds are soluble in This is because they are able to form hydrogen bond with
water molecules.
The solubility decreases with increasing number of carbon atoms. This is because the long
hydrocarbon chain disrupts the hydrogen bonding.
Preparation of Aldehyde and Ketone
Aldehydes, synthesis:
• Oxidation of 1o alcohols
• Oxidation of methylaromatics
• Reduction of acid chlorides
Ketones, synthesis:
• Oxidation of 2o alcohols
• Friedel-Crafts acylation
• Coupling of R2CuLi with acid chloride
1- Oxidation of alcohols
CrO 3/ pyridine O
RCH 2 OH R
Cu / heat H
O
CrO 3/ pyridine
R2CH OH R C R
Cu / heat
