This document provides information on various heterocyclic compounds. It discusses aromatic 5-membered rings including pyrrole, furan, and thiophene which follow Hückel's rule of 4n+2 delocalized pi electrons. Pyrrole is described as a colorless liquid that polymerizes readily upon exposure to air. Its chemical properties include acidification and participation in Ullmann and Bromination reactions. Larger heterocycles such as pyridine and derivatives are also covered, including their structures, aromatic properties, and common biological roles in molecules like vitamins. The document concludes with discussions of purine bases important in nucleic acids and alkaloid stimulants like caffeine that are derived from them.

1. 1
Heterocycles

2. 2
Heterocyclic compounds
Aromatic 5-membered Ring
Heterocycles. Pyrrole, Furan, and
Thiophene.
• Huckel’ Rule 4n+2
N
H
Pyrrole
O
Furan
S
Thiophene
..
..
..
..

3. 3
Hückel's rule estimates whether a planar ring
molecule will have aromatic properties.
•Coplanar structure, with all the contributing
atoms in the same plane
•A delocalized conjugated π system, most
commonly an arrangement of alternating
single and double bonds
•Contributing atoms arranged in one or more rings
•A number of π delocalized electrons that is even,
but not a multiple of 4. That is, 4n + 2 number of π
electrons, where n=0, 1, 2, 3, and so on

4. 4
Pyrrole
Pyrrole is a heterocyclic aromatic organic compound, a five-
membered ring with the formula C4
H4
NH. It is a colourless volatile
liquid that darkens readily upon. s, exposure to air. Substituted
derivatives are also called pyrrole.

5. Pyrrole’s structure.
N-atom electron configuration
7N
sp2
p

6. 6
Chemical Properties. Ur ‘ev’s cycle.
6
O
CH
C
H
C
H
CH
S
CH
C
H
C
H
CH
N
H
CH
C
H
C
H
CH
+ H2S
H2O
NH3
H2O
NH3
H2S
+
+
+
+ +

7. 7
• No basic properties
• Acidic Properties.
N-methylpyrrole
N
H
N
HC
HC
N
H
HC
K
I
I
3
3
3 t+
-
1/2 2
• Pyrrole is acidoforbic:
С4Н4NH +H+
→ С4Н4NH2
+
→ Polymer

8. 8
•Aromatic Properties (SE )
2
2
3
Pyridine sulphotrioxide Sulphopyridine
δ-
δ+ δ+
N
H
N
H
N
H
+ Br
FeBr
-HBr
Br
+Br
Br
Br
Br
Br-HBr
..
N
H
N
H
+ C H N SO SO H + C H N
5 5
. 3 5 53
Bromination
Sulphonation

9. 9
Pyrrole - Pyrroline - Pyrrolidine
Incresing of basity
9
•Hydrogenation
Proline ( Prо)- essential amino acid.

10. 10
Salts of Proline

11. 11
PeptidesGli-Pro-Аlа
• pI=6-7
11
N CH
H
H
NH
O
C
OH
N
H
H
C H
O
C
OH
CH
O
C
O
2
3
NC
O
N
H
CH
CH
O
C
O
CHNH
O
C
3
23
-
+
+2 H2O
H
-2H2O

12. Structure of porphine, the simplest porphyrin.

13. Structure of Heme B
Heme A Heme A is synthesized from Heme B. In two
sequential reactions a 17-hydroxyethylfarnesyl moiety (blue)
is added at the 2-position and an aldehyde (purple) is added
at the 8-position. Nomenclature is shown in green.
The most common type is heme B; other important types
include heme A and heme C. Heme Еcong=840 кJ/mol
13

14. Metabolic Reactions of Triptophane
14
N
H
C H
C HH COOHN
N
O
H
C H
C HH COOHN
H
N
H
C H
C HHN
HO
2
2
2
2
2
2
2
Enzime Enzime
-СО2
5-Hydroxytriptophane
Serotonine
(neiromediator)
N
H
,, N
H
CHCH
NH
COOH
Indole Tryptophane

15. Enzime
-СО2
Triptamine
N
H
C H
C HH COOHN
N
H
C H
C HHN
N
H
C H COOH
N
H
C H
N
H
2
2
2
2
2
2
3
-СО2
Enzime
ScatoleIndole
Enzime

16. 1616
Thiophene
S S
SO H+ H SO 32 4
α-Sulphotiophene
-Н2О
20 °C.
Thiophene is the
heterocyclic compound with
the formula C4H4S.
Consisting of a flat five-
membered ring, it is
aromatic as indicated by its
extensive substitution
reactions.

17. 17
Pentose Furfurol 5-Nitrofurfurole
O
ON HC NR O
ON HC N NH C NH
O
22
Furociline
2
Furan is a heterocyclic organic compound,
consisting of a five-membered aromatic ring
with four carbon atoms and one oxygen. The
class of compounds containing such rings
are also referred to as furans.

18. Vitanim B7 (Biotin)
18
4(Н)
S S
+ 4(Н)
O O
S
N NH H
C
O
HC COOH
+
2( )4
ТГФ
Pd

19. Six-membered Heterocycles
Pyridine
19
Pyridine is a heterocyclic organic compound with the chemical
formula C5H5N. It is structurally related to benzene, with one CH
group replaced by a nitrogen atom.

20. Pyridine’s structure.
N-atom electron configuration
7N
sp2
p
20
pK = 5,2C5H5NH
N
HO H
H Cl
NH
O H
Cl
+
+
+ -
+:
+ -
+
Basic Properties

21. Pyridine was originally industrially produced by
extraction from coal tar.
SE
21
N
Br
FeBr
N
Br
HBr+ 2
3
+
δ+
δ+ δ+
δ- δ-
β-Picoline
Nicotinamide (PP)- Niacin
Nicotinic acid (PP)
Cordiamine
N
CH O
N
C
O
OH
N H
NH
N
C
O
NH
N
C
O
N C H
C H2
2 5
5( )2
( )2
3
3
2
It is a colorless liquid with a distinctive, unpleasant fish-like odor.
The pyridine ring occurs in many important compounds, including
the vitamins nicotinamide and pyridoxal.

22. 22
Name(s) CAS# m.p. (°C) b.p. (°C)
pKa of
pyridinium ion
structure
2-Methylpyridine,
α-picoline
[109-06-8] -66.7 129.4 5.96
3-Methylpyridine,
β-picoline
[108-99-6] -18 141 5.63
4-Methylpyridine,
γ-picoline
[108-89-4] 3.6 145.4 5.98
Picoline refers to three different methylpyridine isomers, all with the chemical formula
C6
H7
N and a molar mass of 93.13 g mol−1
. All three are colourless liquids at room
temperature and pressure and are miscible with water and most organic solvents.Data
for the three compounds are summarized in the table.

23. 23
N
H
NH
+ 6
Pyperidine
N
CH
CH
N
I I+ 3
:
3
δ-δ+
+
-
( )

24. 24
N
C H
H
O N
CH
H
HH
3
2
3
+ +
+
+N
R
N
R
HH
C
O
NHCH H COO H
C
O
NH
C
OH
CH C OO HC
O
H
+
+
2
3
3
+ +
NAD NADН
+
2

25. Azoles
5-membered Heterocycles with two N-atoms
Pyridine’s N
Pyrrole’s
N
Imidazole

26. Prototropic Tautomerism

27. HistamineHistidine

28. 28
Pyrazolone – 5
Thiazole, or 1,3-thiazole, is a heterocyclic compound
that contains both sulfur and nitrogen; the term
'thiazole' also refers to a large family of
derivatives. Thiazole itself is a pale yellow liquid
with a pyridine-like odor and the molecular
formula C3H3NS. The thiazole ring is notable as a
component of the vitamin thiamine (B1).
Thiazole
Pyrazolone, a five-membered-ring
lactam, is a derivative of pyrazole that has
an additional keto (=O) group.

29. Oxazole
Pyrazole refers both to the class of simple
aromatic ring organic compounds of the
heterocyclic series characterized by a 5-
membered ring structure composed of three
carbon atoms and two nitrogen atoms in adjacent
positions, and to the unsubstituted parent
compound. Being so composed and having
pharmacological effects on humans, they are
classified as alkaloids, although they are rare in
nature.
Pyrazole
Oxazole is the parent compound for a vast
class of heterocyclic aromatic organic
compounds. These are azoles with an oxygen
and a nitrogen separated by one carbon.
Oxazoles are aromatic compounds but less so
than the thiazoles. Oxazole is a weak base; its
conjugate acid has a pKa of 0.8, compared to
7 for imidazole.

30. Penicillin (sometimes abbreviated PCN or pen) is a group of
antibiotics derived from Penicillium fungi.Penicillin antibiotics are
historically significant because they are the first drugs that were
effective against many previously serious diseases such as
syphilis and Staphylococcus infections. Penicillins are still widely
used today, though many types of bacteria are now resistant. All
penicillins are Beta-lactam antibiotics and are used in the
treatment of bacterial infections caused by susceptible,
usually Gram-positive, organisms.

31. Azines.
Six-membered Heterocycles with Two Heteroatoms.
Hexazine (also known as hexaazabenzene) is a hypothetical
allotrope of nitrogen composed of 6 nitrogen atoms arranged in a
ring-like structure analogous to that of benzene. It would be the
final member of the azabenzene (azine) series, having all of the
methylidyne groups of the benzene molecule replaced with
nitrogen atoms. The two last members of this series, hexazine
and pentazine, have not been observed, although all other
members of the azine series have (such as pyridine,
pyrimidine, pyridazine, pyrazine, 1,3,5-triazine and tetrazine).

32. Pyridazine
Pyrazine
Pyridazine is a heteroaromatic organic
compound with the molecular formula
C4H4N2, sometimes called 1,2-diazine.
It contains a six-membered ring with
two adjacent nitrogen atoms.
Pyrazine is a heterocyclic aromatic
organic compound. Pyrazine is less
basic in nature than pyridine,
pyridazine and pyrimidine.

33. рКВН =1,3
Pyrimidine
:
:
+ НCl
+ Н2O :
|
H
–
+
Baisic Properties
Pyrimidine is a heterocyclic
aromatic organic compound similar
to benzene and pyridine, containing
two nitrogen atoms at positions 1
and 3 of the six-member ring. It is
isomeric with two other forms of
diazine.

34. :
:
+ Br2
FeBr3
t°
:
:
Br
+ НBr
Aromatic Properties
(SE)
R
R
+
НO
R, R’
Barbituric
acid

35. 35
Barbiturates
C 2H5
C 2H5
C 2H5
C 2H5
+ NaOH
– Н2О
-+
Cl
Thiamine. Vitamin B2

36. Uracil
2,4-Dimethylpyrimidine
Lactim
:
..
Lactam
: :
НН
Thymine
(5 - methyluracil)

37. Citosine
(4 – amino – 2 – hydroxypyrimidine)
:
:
:
..
..

38. Purines.
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine
ring fused to an imidazole ring. Purines, including substituted purines and their
tautomers, are the most widely distributed kind of nitrogen-containing
heterocycle in nature.
пурин
T пл. = 216°С
Adenine
:
..
..
..
: ..
....
HNO2
-N2, -H2O
Hypoxanthine
6- Hydroxypurine
10 ē

39. Guanine
HОNO
Xanthine2,6 -Dihydroxypurine
Guanine (G) is one of the four main nucleobases found in the
nucleic acids DNA and RNA, the others being adenine, cytosine,
and thymine. In DNA, guanine is paired with cytosine. With the
formula C5H5N5O, guanine is a derivative of purine, consisting of a
fused pyrimidine-imidazole ring system with conjugated double
bonds. Being unsaturated, the bicyclic molecule is planar.

40. 40
СН3
1,3,7 – Trimethylxantine
Caffeine
Alkoloids-derivetives of Xanthine
In humans, caffeine acts as a central nervous system (CNS) stimulant, temporarily
warding off drowsiness and restoring alertness. Caffeine is the world's most widely
consumed psychoactive substance, but, unlike many other psychoactive substances, is
legal and unregulated in nearly all jurisdictions.
Caffeine (also spelled caffein) is a bitter, white crystalline xanthine alkaloid
that is a psychoactive stimulant drug. Caffeine was isolated in 1820 by a
German chemist, Friedlieb Ferdinand Runge, and in 1821 by French chemists
working independently; viz., by Robiquet and by Pelletier and Caventou. It was
Pelletier who coined the word "cafeine," whence "caffeine".

41. 41
он
:
.. .. н
н н
+ 2 NaOH NaO
H
NaOH
2,6,8 - Trihydroxypurine
Uric Acid
1)[O] HNO3
2)NH3 изб. Murexide reaction
NH4
Ammonium purpurate

42. 42
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