Heterocyclic Compounds, Nomenclature of Heterocycles, Classification of Heterocyclic Compounds, a) 5-membered Heterocyclic compounds, Preparation of Pyrrole:

1. 1

3. By Dr. Pramod R. Padole
Organic Chemistry
A]
Heterocyclic
compounds:
Unit - III
B]
Organometallic
compounds:

4. LOGO
Heterocyclic Compounds:
By Dr. Pramod R. Padole
(ii) Pyridine:
Synthesis from acetylene and
pentamethylene diamine
hydrochloride,
Basicity (Basic nature),
Electrophilic substitution
reactions (orientation) –
nitration, sulphonation,
Nucleophilic substitution
reactions (orientation)-
with
NaNH2, C6H5Li and KOH
(i) Pyrrole:
Synthesis from acetylene,
succinimide and furan,
Basicity (Basic & Acidic),
Electrophilic substitution
reactions (orientation) –
nitration, sulphonation,
acetylation and
halogenation,
Molecular
orbital structure.
Unit-III
A)
Heterocyclic Compounds

5. pramodpadole@gmail.com
By Dr. Pramod R. Padole
Organometallic compounds:
(i) Grignard reagents:
Methyl magnesium bromide-
Synthesis from methyl bromide
(only reaction)
Synthetic applications:
Electrophilic substitution reactions-
formation of alkanes, alkenes, higher
alkynes and other organometallic
compounds,
Nucleophilic substitution reactions-
Reaction with aldehydes and ketones,
ethylene oxide, acetyl chloride, methyl
cyanide and CO2.
Unit – III
B)
(ii) Methyl lithium:
Synthesis and
Reaction with water,
formaldehyde,
acetaldehyde, acetone,
ethylene oxide and
CO2.

6. LOGO
A) Heterocyclic Compounds:
N
H
2
34
5
1
Pyrrole
N
1 2
3
4
5
6
Pyridine

7. Heterocyclic Compounds:
Defination
Classification
Q.1) What are heterocyclic compounds? How are they classified?
Nomenclature

9. Heterocyclic Compounds or Heterocycles:
Defination:
 The cyclic compounds obtained by replacing
one or more carbon atom of a ring by
heteroatom, like, N, O or S, are called as
heterocyclic compounds.
OR
 Heterocyclic compound, or heterocycles, is
cyclic compound in which one or more of the
atoms of the ring are heteroatoms.
 A heteroatom (such as N, O, S, etc.) is an
atom other than carbon.

10. Heterocyclic Compounds or Heterocycles:
Examples:
The common names of heterocycles are-
N
H
2
34
5
1 O 1
2
34
5
S 1
2
34
5
N
1 2
3
4
5
6
Pyrrole Furan Thiophene Pyridine

11. Nomenclature of Heterocycles:
 Most of the heterocyclic compounds are known by their common
names.
 The name comes from the Greek word heterose, meaning “different”
variety of atoms, such as N, O, S, P, Si, B, Se (Selenium) and As
(Arsenic) can be incorporated (introduced) into ring structures.
 For naming their derivatives, the hetero atom is always numbered as “1”.
 As per Greek nomenclature, the carbon atom next to the hetero atom is
sometimes referred to as the α-carbon atom and those further away as
β- and Ɣ-carbon atoms.
N
H
2
34
5
1
NO2
N
1
2
3
4
5
6 OH
2-nitro Pyrrole (- nitro Pyrrole)
2-hydroxy Pyridine (-hydroxy Pyridine)

12. Nomenclature of Heterocycles:
 Give the names of the following heterocyclic compounds:
2-acetyl-pyrrole 3-nitro-pyridine
N
H
C
O
CH3
(1) (2)
N
NO2
N NH2
(3)
2-amino pyridine
(4)
N C6H5
2-Phenyl pyridine

13. Classification:
Heterocyclic Compounds
5-membered
heterocyclic compounds
6-membered
heterocyclic compounds
Condensed
heterocyclic compounds

14. LOGO 5 – membered heterocyclic Compounds:
These type of compounds contain four
carbon atoms and one hetero atom in a
ring, i.e., total 5-atoms in a ring, are
called as 5-membered heterocyclic
compounds.
 The nitrogen containing five membered heterocycle’s
names usually ends with –ole.
N
H
2
34
5
1 O 1
2
34
5
S 1
2
34
5
Pyrrole Furan Thiophene
Q.1) Pyrrole is a 5 membered hererocyclic compound. (S-13 & W-16, ½ Mark)

15. LOGO
6 – membered hetercyclic compounds:
 These types of compounds contain five carbon
atoms and one hetero atom in a ring, i.e., total
6-atoms in a ring, are called as 6-membered
heterocyclic compounds.
 Example:
 The nitrogen containing six membered heterocycle’s names usually
ends with –ine.
Q.1) Pyridine is a 6 membered hererocyclic compound. (S-19 & W-19 , ½ Mark)
N
1 2
3
4
5
6
Pyridine

16. pramodpadole@gmail.com
By Dr. Pramod R. Padole
Condensed heterocyclic compounds:
These types of compounds contain five or
six membered heterocyclic ring condensed
(fused) with a benzene, are called as
condensed heterocyclic compounds.
Examples:
N 1
2
3
45
6
7
8
9
10
Quinoline
N
1
2
3
45
6
7
8
9
10
Isoquinoline

17. LOGO
a)5-membered Heterocyclic compounds
(i) Pyrrole or Azole:
(Aza-cyclo-penta-2,4-diene) C4H5N
N
H
2
34
5
1
Pyrrole

18. LOGO
Pyrrole or Azole: C4H5N
Pyrrole is a Greek word (Pyrros + Oleum)
meaning is that –
Pyrros = Fairy & Oleum = oil
Pyrrole is an important heterocyclic compound
having five - member ring containing
nitrogen as the heteroatom.
N
H
2
34
5
1
Pyrrole
Molecular Formula of Pyrrole is C4H5N or C4H4NH

19. Methods of Synthesis
or Preparation of Pyrrole:
From
Acetylene
Preparation of Pyrrole
From
Succinimide
From
Furan
Reactions that produce a particular functional group are called preparations
2 acetylene and ammonia
enol form, which on distillation
with Zinc dust
Furan + NH3
heated alumina
400oC - 500oC

20. Preparation of Pyrrole from Acetylene:
From Acetylene:
When mixture of acetylene (2 equivalents)
and ammonia is passing through a red
hot tube; to form pyrrole.
CH
HC
HC
CH
H-N H
Red Hot Iron Tube
N
H
H2
Pyrrole
H
(or NH3)
Q.1) How will you prepare / obtain pyrrole from acetylene? (S-13 & W-19, 2 Mark)
Q.2) What happens when mixture of acetylene and ammonia is passed through red hot tube?
(S-14 & W-16, 2 Mark)

21. Preparation of Pyrrole
from Succinimide:
H2C
C
H2C
C
O
O
N H
Succinimide ( Keto form)
H2C
C
H2C
C
O
O
OH
OH
Succinic acid
+
H
H
N H
?

22. Preparation of Pyrrole from Succinimide:
Or By distillating Succinimide with Zn-dust:
 From Succinimide:
When Succinimide (Keto form) isomerizes to enol form,
which on distillation with Zinc dust; to form pyrrole.
Q.1) How will you obtain: Pyrrole form succinimide? (S-16 & S-17, 2 Mark)
Q.2) Pyrrole can be synthesized by distilling Succinimide with zinc dust. (S-17, ½ Mark)
Q.3) How will you prepare: Pyrrole form succinimide? (W-17, 2 Mark)
Q.4) Give the synthesis of Pyrrole from succinimide. (W-18, 2 Mark)
Q.5) Write method of synthesis of Pyrrole from succinimide. (S-19, 2 Mark)
H2C
C
CH2
C
O O
N
H
HC CH
C C
N
HO OH
H
HC CH
HC CH
N
H
Succinimide ( Keto form)
(Enol form) Pyrrole
+ 2 Zn-dustIsomerisation
+ 2 ZnO
On distillation
with

23. LOGOPreparation of Pyrrole from Furan:
Or Reaction with Furan and NH3 over alumina:
Or Industrial / Commercial Method of Pyrrole:
From Furan:
When mixture of furan and ammonia is passed over heated alumina
(Al2O3) as a catalyst at about 400oC - 500oC; to form pyrrole.
O
H2 N-H
or NH3
Furan
Al2O3
N
H
Pyrrole
H2O
Ammonia
400-500o
C
Catalyst
Q.1) How will you obtain Pyrrole from Furan? (W-11, S-12 & S-18, 2 Mark)
Q.2) How will you convert Furan to pyrrole? (W-13, 2 Mark)
Q.3) How will you synthesize Pyrrole from Furan? (W-15, 2 Mark)
Q.4) Write method of synthesis of Pyrrole from Furan. (S-19, 2 Mark)

24. LOGOPreparation of Pyrrole from Furan:
Or Reaction with Furan and NH3 over alumina:
Or Industrial / Commercial Method of Pyrrole:
From Furan:
When mixture of furan and ammonia is passed over heated alumina
(Al2O3) as a catalyst at about 400oC - 500oC; to form pyrrole.
Q.1) How will you obtain Pyrrole from Furan? (W-11, S-12 & S-18, 2 Mark)
Q.2) How will you convert Furan to pyrrole? (W-13, 2 Mark)
Q.3) How will you synthesize Pyrrole from Furan? (W-15, 2 Mark)
Q.4) Write method of synthesis of Pyrrole from Furan. (S-19, 2 Mark)
OFuran
Ammonia
H2
N
H
or NH3
+ N
H
Pyrrole
H2OAl2O3
400-500o
C
Catalyst
heated

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Heterocyclic Compounds by Dr Pramod R. Padole
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