NCERT Textbook: Aldehydes, Ketones & Carboxylic Acids | Chemistry Class 12 - NEET PDF Download

 Page 1


After studying this Unit, you will be
able to
• write the common  and IUPAC
names of aldehydes, ketones and
carboxylic acids;
• write the structures of the
compounds containing functional
groups namely carbonyl and
carboxyl groups;
• describe the important methods
of preparation and reactions of
these classes of compounds;
• correlate physical properties and
chemical reactions of aldehydes,
ketones and carboxylic acids,
with their structures;
• explain the mechanism of a few
selected reactions of aldehydes
and ketones;
• understand various factors
affecting the acidity of carboxylic
acids and their reactions;
• describe the uses of aldehydes,
ketones and carboxylic acids.
Objectives
Carbonyl compounds are of utmost importance to organic
chemistry. They are constituents of fabrics, flavourings, plastics
and drugs.
8
Unit Unit Unit Unit Unit
8
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
In the previous Unit, you have studied organic
compounds with functional groups containing carbon-
oxygen single bond. In this Unit, we will study about the
organic compounds containing carbon-oxygen double
bond (>C=O) called carbonyl group, which is one of the
most important functional groups in organic chemistry.
In aldehydes, the carbonyl group is bonded to a
carbon and hydrogen while in the ketones, it is bonded
to two carbon atoms. The carbonyl compounds in which
carbon of carbonyl group is bonded to carbon or
hydrogen and oxygen of hydroxyl moiety (-OH) are
known as carboxylic acids, while in compounds where
carbon is attached to carbon or hydrogen and nitrogen
of -NH
2
 moiety or to halogens are called amides and
acyl halides respectively. Esters and anhydrides are
derivatives of carboxylic acids. The general formulas of
these classes of compounds are given below:
Reprint 2024-25
Page 2


After studying this Unit, you will be
able to
• write the common  and IUPAC
names of aldehydes, ketones and
carboxylic acids;
• write the structures of the
compounds containing functional
groups namely carbonyl and
carboxyl groups;
• describe the important methods
of preparation and reactions of
these classes of compounds;
• correlate physical properties and
chemical reactions of aldehydes,
ketones and carboxylic acids,
with their structures;
• explain the mechanism of a few
selected reactions of aldehydes
and ketones;
• understand various factors
affecting the acidity of carboxylic
acids and their reactions;
• describe the uses of aldehydes,
ketones and carboxylic acids.
Objectives
Carbonyl compounds are of utmost importance to organic
chemistry. They are constituents of fabrics, flavourings, plastics
and drugs.
8
Unit Unit Unit Unit Unit
8
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
In the previous Unit, you have studied organic
compounds with functional groups containing carbon-
oxygen single bond. In this Unit, we will study about the
organic compounds containing carbon-oxygen double
bond (>C=O) called carbonyl group, which is one of the
most important functional groups in organic chemistry.
In aldehydes, the carbonyl group is bonded to a
carbon and hydrogen while in the ketones, it is bonded
to two carbon atoms. The carbonyl compounds in which
carbon of carbonyl group is bonded to carbon or
hydrogen and oxygen of hydroxyl moiety (-OH) are
known as carboxylic acids, while in compounds where
carbon is attached to carbon or hydrogen and nitrogen
of -NH
2
 moiety or to halogens are called amides and
acyl halides respectively. Esters and anhydrides are
derivatives of carboxylic acids. The general formulas of
these classes of compounds are given below:
Reprint 2024-25
228 Chemistry
Aldehydes, ketones and carboxylic acids are widespread in plants
and animal kingdom. They play an important role in biochemical
processes of life. They add fragrance and flavour to nature, for example,
vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and
cinnamaldehyde (from cinnamon) have very pleasant fragrances.
8.1.1
Nomenclature
I. Aldehydes and ketones
Aldehydes and ketones are the simplest and most important carbonyl
compounds.
There are two systems of nomenclature of aldehydes and ketones.
(a) Common names
Aldehydes and ketones are often called by their common names
instead of IUPAC names. The common names of most aldehydes are
derived from the common names of the corresponding carboxylic
acids [Section 8.6.1] by replacing the ending –ic of acid with aldehyde.
At the same time, the names reflect the Latin or Greek term for the
original source of the acid or aldehyde. The location of the substituent
in the carbon chain is indicated by Greek letters a, b, g, d, etc. The
a-carbon being the one directly linked to the aldehyde group, b-
carbon the next, and so on. For example
8.1 8.1 8.1 8.1 8.1 Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group
They are used in many food products and pharmaceuticals to add
flavours. Some of these families are manufactured for use as solvents
(i.e., acetone) and for preparing materials like adhesives, paints, resins,
perfumes, plastics, fabrics, etc.
Reprint 2024-25
Page 3


After studying this Unit, you will be
able to
• write the common  and IUPAC
names of aldehydes, ketones and
carboxylic acids;
• write the structures of the
compounds containing functional
groups namely carbonyl and
carboxyl groups;
• describe the important methods
of preparation and reactions of
these classes of compounds;
• correlate physical properties and
chemical reactions of aldehydes,
ketones and carboxylic acids,
with their structures;
• explain the mechanism of a few
selected reactions of aldehydes
and ketones;
• understand various factors
affecting the acidity of carboxylic
acids and their reactions;
• describe the uses of aldehydes,
ketones and carboxylic acids.
Objectives
Carbonyl compounds are of utmost importance to organic
chemistry. They are constituents of fabrics, flavourings, plastics
and drugs.
8
Unit Unit Unit Unit Unit
8
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
In the previous Unit, you have studied organic
compounds with functional groups containing carbon-
oxygen single bond. In this Unit, we will study about the
organic compounds containing carbon-oxygen double
bond (>C=O) called carbonyl group, which is one of the
most important functional groups in organic chemistry.
In aldehydes, the carbonyl group is bonded to a
carbon and hydrogen while in the ketones, it is bonded
to two carbon atoms. The carbonyl compounds in which
carbon of carbonyl group is bonded to carbon or
hydrogen and oxygen of hydroxyl moiety (-OH) are
known as carboxylic acids, while in compounds where
carbon is attached to carbon or hydrogen and nitrogen
of -NH
2
 moiety or to halogens are called amides and
acyl halides respectively. Esters and anhydrides are
derivatives of carboxylic acids. The general formulas of
these classes of compounds are given below:
Reprint 2024-25
228 Chemistry
Aldehydes, ketones and carboxylic acids are widespread in plants
and animal kingdom. They play an important role in biochemical
processes of life. They add fragrance and flavour to nature, for example,
vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and
cinnamaldehyde (from cinnamon) have very pleasant fragrances.
8.1.1
Nomenclature
I. Aldehydes and ketones
Aldehydes and ketones are the simplest and most important carbonyl
compounds.
There are two systems of nomenclature of aldehydes and ketones.
(a) Common names
Aldehydes and ketones are often called by their common names
instead of IUPAC names. The common names of most aldehydes are
derived from the common names of the corresponding carboxylic
acids [Section 8.6.1] by replacing the ending –ic of acid with aldehyde.
At the same time, the names reflect the Latin or Greek term for the
original source of the acid or aldehyde. The location of the substituent
in the carbon chain is indicated by Greek letters a, b, g, d, etc. The
a-carbon being the one directly linked to the aldehyde group, b-
carbon the next, and so on. For example
8.1 8.1 8.1 8.1 8.1 Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group
They are used in many food products and pharmaceuticals to add
flavours. Some of these families are manufactured for use as solvents
(i.e., acetone) and for preparing materials like adhesives, paints, resins,
perfumes, plastics, fabrics, etc.
Reprint 2024-25
229 Aldehydes, Ketones and Carboxylic Acids
The common names of ketones are derived by naming two alkyl
or aryl groups bonded to the carbonyl group. The locations of
substituents are indicated by Greek letters, a a¢, b b¢ and so on
beginning with the carbon atoms next to the carbonyl group,
indicated as aa¢. Some ketones have historical common names,
the simplest dimethyl ketone is called acetone. Alkyl phenyl
ketones are usually named by adding the name of acyl group as
prefix to the word phenone. For example
(b) IUPAC names
The IUPAC names of open chain aliphatic aldehydes and ketones
are derived from the names of the corresponding alkanes by
replacing the ending –e with –al and –one respectively. In case of
aldehydes the longest carbon chain is numbered starting from the
carbon of the aldehyde group while in case of ketones the
numbering begins from the end nearer to the carbonyl group. The
substituents are prefixed in alphabetical order along with numerals
indicating their positions in the carbon chain. The same applies to
cyclic ketones, where the carbonyl carbon is numbered one. When
the aldehyde group is attached to a ring, the suffix carbaldehyde
is added after the full name of the cycloalkane. The numbering of
the ring carbon atoms start from the carbon atom attached to the
aldehyde group. The name of the simplest aromatic aldehyde
carrying the aldehyde group on a benzene ring is
benzenecarbaldehyde. However, the common name benzaldehyde
is also accepted by IUPAC. Other aromatic aldehydes are hence
named as substituted benzaldehydes.
Reprint 2024-25
Page 4


After studying this Unit, you will be
able to
• write the common  and IUPAC
names of aldehydes, ketones and
carboxylic acids;
• write the structures of the
compounds containing functional
groups namely carbonyl and
carboxyl groups;
• describe the important methods
of preparation and reactions of
these classes of compounds;
• correlate physical properties and
chemical reactions of aldehydes,
ketones and carboxylic acids,
with their structures;
• explain the mechanism of a few
selected reactions of aldehydes
and ketones;
• understand various factors
affecting the acidity of carboxylic
acids and their reactions;
• describe the uses of aldehydes,
ketones and carboxylic acids.
Objectives
Carbonyl compounds are of utmost importance to organic
chemistry. They are constituents of fabrics, flavourings, plastics
and drugs.
8
Unit Unit Unit Unit Unit
8
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
In the previous Unit, you have studied organic
compounds with functional groups containing carbon-
oxygen single bond. In this Unit, we will study about the
organic compounds containing carbon-oxygen double
bond (>C=O) called carbonyl group, which is one of the
most important functional groups in organic chemistry.
In aldehydes, the carbonyl group is bonded to a
carbon and hydrogen while in the ketones, it is bonded
to two carbon atoms. The carbonyl compounds in which
carbon of carbonyl group is bonded to carbon or
hydrogen and oxygen of hydroxyl moiety (-OH) are
known as carboxylic acids, while in compounds where
carbon is attached to carbon or hydrogen and nitrogen
of -NH
2
 moiety or to halogens are called amides and
acyl halides respectively. Esters and anhydrides are
derivatives of carboxylic acids. The general formulas of
these classes of compounds are given below:
Reprint 2024-25
228 Chemistry
Aldehydes, ketones and carboxylic acids are widespread in plants
and animal kingdom. They play an important role in biochemical
processes of life. They add fragrance and flavour to nature, for example,
vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and
cinnamaldehyde (from cinnamon) have very pleasant fragrances.
8.1.1
Nomenclature
I. Aldehydes and ketones
Aldehydes and ketones are the simplest and most important carbonyl
compounds.
There are two systems of nomenclature of aldehydes and ketones.
(a) Common names
Aldehydes and ketones are often called by their common names
instead of IUPAC names. The common names of most aldehydes are
derived from the common names of the corresponding carboxylic
acids [Section 8.6.1] by replacing the ending –ic of acid with aldehyde.
At the same time, the names reflect the Latin or Greek term for the
original source of the acid or aldehyde. The location of the substituent
in the carbon chain is indicated by Greek letters a, b, g, d, etc. The
a-carbon being the one directly linked to the aldehyde group, b-
carbon the next, and so on. For example
8.1 8.1 8.1 8.1 8.1 Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group
They are used in many food products and pharmaceuticals to add
flavours. Some of these families are manufactured for use as solvents
(i.e., acetone) and for preparing materials like adhesives, paints, resins,
perfumes, plastics, fabrics, etc.
Reprint 2024-25
229 Aldehydes, Ketones and Carboxylic Acids
The common names of ketones are derived by naming two alkyl
or aryl groups bonded to the carbonyl group. The locations of
substituents are indicated by Greek letters, a a¢, b b¢ and so on
beginning with the carbon atoms next to the carbonyl group,
indicated as aa¢. Some ketones have historical common names,
the simplest dimethyl ketone is called acetone. Alkyl phenyl
ketones are usually named by adding the name of acyl group as
prefix to the word phenone. For example
(b) IUPAC names
The IUPAC names of open chain aliphatic aldehydes and ketones
are derived from the names of the corresponding alkanes by
replacing the ending –e with –al and –one respectively. In case of
aldehydes the longest carbon chain is numbered starting from the
carbon of the aldehyde group while in case of ketones the
numbering begins from the end nearer to the carbonyl group. The
substituents are prefixed in alphabetical order along with numerals
indicating their positions in the carbon chain. The same applies to
cyclic ketones, where the carbonyl carbon is numbered one. When
the aldehyde group is attached to a ring, the suffix carbaldehyde
is added after the full name of the cycloalkane. The numbering of
the ring carbon atoms start from the carbon atom attached to the
aldehyde group. The name of the simplest aromatic aldehyde
carrying the aldehyde group on a benzene ring is
benzenecarbaldehyde. However, the common name benzaldehyde
is also accepted by IUPAC. Other aromatic aldehydes are hence
named as substituted benzaldehydes.
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230 Chemistry
Aldehydes
HCHO Formaldehyde Methanal
CH
3
CHO Acetaldehyde Ethanal
(CH
3
)
2
CHCHO Isobutyraldehyde 2-Methylpropanal
g-Methylcyclohexanecarbaldehyde 3-Methylcyclohexanecarbaldehyde
CH
3
CH(OCH
3
)CHO a-Methoxypropionaldehyde 2-Methoxypropanal
CH
3
CH
2
CH
2
CH
2
CHO Valeraldehyde Pentanal
CH
2
=CHCHO Acrolein Prop-2-enal
Phthaldehyde Benzene-1,2-dicarbaldehyde
m-Bromobenzaldehyde 3-Bromobenzaldehyde
Ketones
CH
3
COCH
2
CH
2
CH
3
Methyl n-propyl ketone Pentan-2-one
(CH
3
)
2
CHCOCH(CH
3
)
2
Diisopropyl ketone 2,4-Dimethylpentan-3-one
a-Methylcyclohexanone 2-Methylcyclohexanone
(CH
3
)
2
C=CHCOCH
3
Mesityl oxide 4-Methylpent-3-en-2-one
Table 8.1: Common and IUPAC Names of Some Aldehydes and Ketones
Structure Common name IUPAC name
The common and IUPAC names of some aldehydes and ketones are
given in Table 8.1.
or
3-Bromobenzenecarbaldehyde
Reprint 2024-25
Page 5


After studying this Unit, you will be
able to
• write the common  and IUPAC
names of aldehydes, ketones and
carboxylic acids;
• write the structures of the
compounds containing functional
groups namely carbonyl and
carboxyl groups;
• describe the important methods
of preparation and reactions of
these classes of compounds;
• correlate physical properties and
chemical reactions of aldehydes,
ketones and carboxylic acids,
with their structures;
• explain the mechanism of a few
selected reactions of aldehydes
and ketones;
• understand various factors
affecting the acidity of carboxylic
acids and their reactions;
• describe the uses of aldehydes,
ketones and carboxylic acids.
Objectives
Carbonyl compounds are of utmost importance to organic
chemistry. They are constituents of fabrics, flavourings, plastics
and drugs.
8
Unit Unit Unit Unit Unit
8
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
Aldehydes Aldehydes Aldehydes Aldehydes Aldehydes, , , , ,     K K K K Ke e e e etones tones tones tones tones
and and and and and     Carboxylic Carboxylic Carboxylic Carboxylic Carboxylic
A A A A Acids cids cids cids cids
In the previous Unit, you have studied organic
compounds with functional groups containing carbon-
oxygen single bond. In this Unit, we will study about the
organic compounds containing carbon-oxygen double
bond (>C=O) called carbonyl group, which is one of the
most important functional groups in organic chemistry.
In aldehydes, the carbonyl group is bonded to a
carbon and hydrogen while in the ketones, it is bonded
to two carbon atoms. The carbonyl compounds in which
carbon of carbonyl group is bonded to carbon or
hydrogen and oxygen of hydroxyl moiety (-OH) are
known as carboxylic acids, while in compounds where
carbon is attached to carbon or hydrogen and nitrogen
of -NH
2
 moiety or to halogens are called amides and
acyl halides respectively. Esters and anhydrides are
derivatives of carboxylic acids. The general formulas of
these classes of compounds are given below:
Reprint 2024-25
228 Chemistry
Aldehydes, ketones and carboxylic acids are widespread in plants
and animal kingdom. They play an important role in biochemical
processes of life. They add fragrance and flavour to nature, for example,
vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and
cinnamaldehyde (from cinnamon) have very pleasant fragrances.
8.1.1
Nomenclature
I. Aldehydes and ketones
Aldehydes and ketones are the simplest and most important carbonyl
compounds.
There are two systems of nomenclature of aldehydes and ketones.
(a) Common names
Aldehydes and ketones are often called by their common names
instead of IUPAC names. The common names of most aldehydes are
derived from the common names of the corresponding carboxylic
acids [Section 8.6.1] by replacing the ending –ic of acid with aldehyde.
At the same time, the names reflect the Latin or Greek term for the
original source of the acid or aldehyde. The location of the substituent
in the carbon chain is indicated by Greek letters a, b, g, d, etc. The
a-carbon being the one directly linked to the aldehyde group, b-
carbon the next, and so on. For example
8.1 8.1 8.1 8.1 8.1 Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group Nomenclature and Structure of Carbonyl Group
They are used in many food products and pharmaceuticals to add
flavours. Some of these families are manufactured for use as solvents
(i.e., acetone) and for preparing materials like adhesives, paints, resins,
perfumes, plastics, fabrics, etc.
Reprint 2024-25
229 Aldehydes, Ketones and Carboxylic Acids
The common names of ketones are derived by naming two alkyl
or aryl groups bonded to the carbonyl group. The locations of
substituents are indicated by Greek letters, a a¢, b b¢ and so on
beginning with the carbon atoms next to the carbonyl group,
indicated as aa¢. Some ketones have historical common names,
the simplest dimethyl ketone is called acetone. Alkyl phenyl
ketones are usually named by adding the name of acyl group as
prefix to the word phenone. For example
(b) IUPAC names
The IUPAC names of open chain aliphatic aldehydes and ketones
are derived from the names of the corresponding alkanes by
replacing the ending –e with –al and –one respectively. In case of
aldehydes the longest carbon chain is numbered starting from the
carbon of the aldehyde group while in case of ketones the
numbering begins from the end nearer to the carbonyl group. The
substituents are prefixed in alphabetical order along with numerals
indicating their positions in the carbon chain. The same applies to
cyclic ketones, where the carbonyl carbon is numbered one. When
the aldehyde group is attached to a ring, the suffix carbaldehyde
is added after the full name of the cycloalkane. The numbering of
the ring carbon atoms start from the carbon atom attached to the
aldehyde group. The name of the simplest aromatic aldehyde
carrying the aldehyde group on a benzene ring is
benzenecarbaldehyde. However, the common name benzaldehyde
is also accepted by IUPAC. Other aromatic aldehydes are hence
named as substituted benzaldehydes.
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230 Chemistry
Aldehydes
HCHO Formaldehyde Methanal
CH
3
CHO Acetaldehyde Ethanal
(CH
3
)
2
CHCHO Isobutyraldehyde 2-Methylpropanal
g-Methylcyclohexanecarbaldehyde 3-Methylcyclohexanecarbaldehyde
CH
3
CH(OCH
3
)CHO a-Methoxypropionaldehyde 2-Methoxypropanal
CH
3
CH
2
CH
2
CH
2
CHO Valeraldehyde Pentanal
CH
2
=CHCHO Acrolein Prop-2-enal
Phthaldehyde Benzene-1,2-dicarbaldehyde
m-Bromobenzaldehyde 3-Bromobenzaldehyde
Ketones
CH
3
COCH
2
CH
2
CH
3
Methyl n-propyl ketone Pentan-2-one
(CH
3
)
2
CHCOCH(CH
3
)
2
Diisopropyl ketone 2,4-Dimethylpentan-3-one
a-Methylcyclohexanone 2-Methylcyclohexanone
(CH
3
)
2
C=CHCOCH
3
Mesityl oxide 4-Methylpent-3-en-2-one
Table 8.1: Common and IUPAC Names of Some Aldehydes and Ketones
Structure Common name IUPAC name
The common and IUPAC names of some aldehydes and ketones are
given in Table 8.1.
or
3-Bromobenzenecarbaldehyde
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231 Aldehydes, Ketones and Carboxylic Acids
The carbonyl carbon atom is sp
2
-hybridised and forms three sigma (s)
bonds. The fourth valence electron of carbon remains in its p-orbital
and forms a p-bond with oxygen by overlap with p-orbital of an oxygen.
In addition, the oxygen atom also has two non bonding electron pairs.
Thus, the carbonyl carbon and the three atoms attached to it lie in the
same plane and the p-electron cloud is above and below this plane. The
bond angles are approximately 120° as expected of a trigonal coplanar
structure (Figure 8.1).
8.1.2 Structure of
the
Carbonyl
Group
p
Fig.8.1  Orbital diagram for the formation of carbonyl group
The carbon-oxygen double bond is polarised due to higher
electronegativity of oxygen relative to carbon. Hence, the carbonyl
carbon is an electrophilic (Lewis acid), and carbonyl
oxygen, a nucleophilic (Lewis base) centre. Carbonyl
compounds have substantial dipole moments and are
polar than ethers. The high polarity of the carbonyl group
is explained on the basis of resonance involving a neutral
(A) and a dipolar (B) structures as shown.
Intext Questions Intext Questions Intext Questions Intext Questions Intext Questions
8.1 Write the structures of the following compounds.
(i) a-Methoxypropionaldehyde (ii) 3-Hydroxybutanal
(iii) 2-Hydroxycyclopentane carbaldehyde (iv) 4-Oxopentanal
(v) Di-sec. butyl ketone (vi) 4-Fluoroacetophenone
Some important methods for the preparation of aldehydes
and ketones are as follows:
1. By oxidation of alcohols
Aldehydes and ketones are generally prepared by oxidation of primary
and secondary alcohols, respectively (Unit 7, Class XII).
2. By dehydrogenation of alcohols
This method is suitable for volatile alcohols and is of industrial
application. In this method alcohol vapours are passed over heavy
metal catalysts (Ag or Cu). Primary and secondary alcohols give
aldehydes and ketones, respectively (Unit 7, Class XII).
3. From hydrocarbons
(i) By ozonolysis of alkenes: As we know, ozonolysis of alkenes
followed by reaction with zinc dust and water gives aldehydes,
8.2.1 Preparation
of
Aldehydes
and
Ketones
8.2 8.2 8.2 8.2 8.2 Preparation of Aldehydes Preparation of Aldehydes Preparation of Aldehydes Preparation of Aldehydes Preparation of Aldehydes
and Ketones and Ketones and Ketones and Ketones and Ketones
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