aldehyde, any of a class of organic compounds in which a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms (designated R in general chemical formulas and structure diagrams).

1. CLASS XII
NAME REACTION
ALDEHYDES, KETONES
& CARBOXYLIC ACID
PRESENTED BY
BRAJENDRA KUMAR PATEL
PGT CHEMISTRY
JAWAHAR NAVODAYA
VIDYALAYA
MOB. 9893179244

2. INDEX
15. OZONOLYSIS
14. ROSENMUND REDUCTION
3. STEPHEN REACTION
8. ETARD REACTION
2. GATTERMAN KOACH REACTION
5. ALDOL CONDENSATION 6. CROSS ALDOL CONDENSATION
12. CANNIZARO REACTION
1. DECRBOXYLATION
7. HELL VOLHARD ZELINSKY (HVZ)
9. CLEMENSON REDUCTION
4. WOLF KISHNER REDUCTION
11. BENZOIN CONDESATION
10. CLAISEN CONDENSATION
13. TISCHENKO REACTION

3. 1. DECRBOXYLATION
Sodium salts of carboxylic acid on heating with soda lime
loses one carbon atom and form alkane.
R–H
R–COONa
NaOH
CaO
+ Na2CO3
Sodium salt of acid Alkane Sodium Carbonate
CH4
CH3–COONa NaOH
CaO
+ Na2CO3
Sodium ethanoate Methane Sodium Carbonate
C2H6
C2H5–COONa NaOH
CaO
+ Na2CO3
Sodium propanoate Ethane Sodium Carbonate

4. 2. GATTERMAN KOACH REACTION
When benzene or its derivative is treated with
carbon monoxide and hydrogen chloride in the presence
of anhydrous aluminium chloride or cuprous chloride, it
gives benzaldehyde or substituted benzaldehyde.
CO + HCl
Anhy. AlCl3
Toluene Benzaldehyde.
CHO

5. 3. STEPHEN REACTION
Nitriles (cynaides) are reduced to corresponding imine
with stannous chloride in the presence of hydrochloric
acid, which on hydrolysis give corresponding aldehyde.
H+
RCHO
RCH=NH
SnCl2 + HCl
RCN
H+
CH3–CHO
CH3–CH=NH
SnCl2 + HCl
CH3–CN
Aldehyde
imine
Alkyl Nitrile
Ethanal
Ethannitrile

6. 4. WOLF KISHNER REDUCTION
The reduction of aldehyde or ketone (carbonyl CO group)
to alkane by heating with hydrazine and KOH in
ethylene glycol is called wolf kishner reduction.
R–C–H
O
NH2NH2 / KOH,
glycol 453-473K R–CH3 + N2
R–C–R
O
NH2NH2 / KOH,
glycol 453-473K
R–CH2–R + N2
Ar–C–H
O
NH2NH2 / KOH,
glycol 453-473K
Ar–CH2–R + N2

7. 5. ALDOL CONDENSATION
Aldehydes and ketones having at least one α-hydrogen undergo a
reaction in the presence of dilute alkali as catalyst to form β-
hydroxy aldehydes (aldol) or β-hydroxy ketones (ketol), which
readily lose water to give α,β-nsaturated carbonyl compounds.
CH3–C
Ethanal
O
CH3–CH–CH2–CHO
OH
+ –H2O
CH3–CH=CH–CHO
2-hydroxybutanal
But-2-enal
–H
CH3–C
O
–H

8. 5. ALDOL CONDENSATION
Aldehydes and ketones having at least one α-hydrogen undergo a
reaction in the presence of dilute alkali as catalyst to form β-
hydroxy aldehydes (aldol) or β-hydroxy ketones (ketol), which
readily lose water to give α,β-nsaturated carbonyl compounds.
CH3–C – CH3
Ethanone
O
CH3–C–CH2–C–CH3
+ –H2O
CH3–C – CH3
O
OH
CH3
O
CH3–C=CH–C–CH3
CH3
O
4-hydroxy-4-methyl
pentane-2-one
4-methyl pent-2-en-2-one

9. 6. CROSS ALDOL CONDENSATION
When aldol condensation is carried out between two
different aldehydes and / or ketones, it is called cross
aldol condensation. If both of them contain α-hydrogen
atoms, it gives a mixture of four products.
CH3–CHO
CH3–CH2–CHO
+
CH3–C=CH–CHO
CH3–CH2–CH=C–CHO
CH3–C=C–CHO
CH3–CH2–CH=CH–CHO
CH3
CH3
2 molecules
of ethanal
2 molecules
of propanal
Propanal and
ethanal
Propanal and
ethanal
But-2-enal
2-methyl
pent-2-enal
Pent-2-enal
2-methyl but-2-enal

10. 7. HELL VOLHARD ZELINSKY (HVZ)
Carboxylic acid react with chlorine or bromine in
presence of small quantity of red phosphorous to give
α – chloro or α – bromo carboxylic acid.
R–CH2X–COOH
R–CH2–COOH X2, Red P
H2O
X =
Cl, Br
Carboxylic acid α–halo Carboxylic acid
CH2Cl–COOH
CH3–COOH Cl2, Red P
H2O
ethanoic acid α–chloro ethanoic acid
CHCl2–COOH
CH2Cl–COOH Cl2, Red P
H2O
α, α–dichloro ethanoic acid

11. 8. ETARD REACTION
Chromyl chloride oxidises methyl group to a chromium
complex, which on hydrolysis gives corresponding
benzaldehyde.
CH3
CrO2Cl2
CS2
CH(OCrOHCl3)2
H3O+
CHO
Toluene Chromium
Complex
benzaldehyde

12. 9. CLEMENSON REDUCTION
The reduction of aldehyde or ketone (carbonyl CO group)
to alkane with amalgamated zinc and concentrated
hydrochloride acid.
R–C–H
O
+ 4[H]
Zn/Hg + Conc. HCl
R–CH3 + H2O
R–C–R
O
+ 4[H]
Zn/Hg + Conc. HCl
R–CH2–R + H2O
Ar–C–H
O
+ 4[H]
Zn/Hg + Conc. HCl
Ar–CH2–R + H2O

13. 10. CLAISEN CONDENSATION
The self condensation of two molecules of an ester
containing α hydrogen in presence of a strong base
such as sodium ethoxide to form α – keto ester is
called claisen condensation.
CH3–C–O–C2H5
O
+ CH3–C–O–C2H5
O
C2H5ONa
CH3–C–
O
CH2–C–O–C2H5
O
Ethylacetoacetate

14. 11. BENZOIN CONDESATION
Two molecules of benzaldehyde undergo condensation
on heating with alc. KCN to form benzoins. The
reaction is called benzoin condensation.
C–H
O
H–C
O
+
Alc. KCN
C
OH
H
C
O

15. 12. CANNIZARO REACTION
Aldehydes which do not have an α-hydrogen atom, undergo self
oxidation and reduction (disproportionation) reaction on heating
with concentrated alkali. In this reaction, one molecule of the
aldehyde is reduced to alcohol while another is oxidised to
carboxylic acid salt.
CH3–OH
2H–CHO
KOH
Δ
+ H–COOK
Benzaldehyde
CHO
KOH
Δ
Benzyl alcohol
CH2OH
Potassium benzoate
H–COOK
+
Methanal Methanol Potassium methanoat

16. 13. TISCHENKO REACTION
All aldehydes (with or without hydrogen) can undergo
cannizzaro reaction on treatment with aluminium
ethoxide. The products further combine to form ester.
2CH3–CHO
Eth-Al CH3–COOH
+
CH3–CH2–OH
CH3–COOC2H5
-H2O
CH3–C
O
H
+ C–CH3
O
H
Al(C2H5O)3
CH3–C–O–CH2CH3
O

17. 14. ROSENMUND REDUCTION
Acyl chloride (acid chloride) is reduced in presence of
palladised barium sulphate to form aldehyde.
R–C–H
R–C–Cl Pd/BaSO4
H2
+ HCl
O O
CH3–C–H
CH3–C–Cl Pd/BaSO4
H2
+ HCl
O O
C–Cl Pd/BaSO4
H2
+ HCl
O
C–H
O

18. 15. OZONOLYSIS
C=C
O3
C –O – C
H2O
O O
C
O
C
O
+
H2C=CH2
O3
H2C –O – CH2
H2O2
O O
H2C
O
CH2
O
+
H–C=C–H
O3
H–C –O – C–H
H2O2
O O
H–C
O
C–H
O
+
R R R R R R
Ozonide
Alkene
Aldehyde or ketone
–H2O2
Ethene

19. 15. OZONOLYSIS
C=C
O3
C –O – C
H2O
O O
C
O
C
O
+
R–C=C–R
O3
R–C –O – C–R
H2O2
O O
R–C
O
C–R
O
+
R R R R R R
Ozonide
Alkene
Aldehyde or ketone
–H2O2