Introduction Heterocyclic compound is one wich possess a

Introduction Heterocyclic compound is one wich possess a cyclic structure with at least two different kinds of atoms in the rings. The most common type, contain largely carbon atoms Nitrogen , Oxygen and Sulphur are the most common hetero atoms. Heterocyclic compounds are very widely distributed in nature , and essential to life in various ways. Most of sugar , and their derivatives including vatamine c , Vitamin B 6 , alkaloide and antibiotic Heterocyclic compounds can be aliphatic or Aromatic in character depending upon their electronic constituents. In general , the aliphatic heterocyclic compounds are very similar to their open chain aliphatic analognes for e. g. 1 lec 1

Tetrahydrofuran (1) has many properties characteristic to diethyl ether (11) In a similar way the aromatic heterocyclic have many properties resembling their aromatic carbo cyclic analogues for example pyridine (III) and benzene (IV) (III) 2 (IV) lec 1

Classification of Heterocyclic compounds A – One ring 1 – Three – Membered Mono heterocycles 2 – Four – membered Mono heterocycles 3 lec 1

3 – Five – membered Mono heterocycles 4 – Five membered di heterocycles 4 lec 1

5 – Five – membered triheterocycles 4 N 5 N 3 N | H 1 2 1, 3, 4 - triazole 4 N 5 3 N |1 H N 2 1, 2, 4 - triazole 6 – Six – membered monoheterocycles 5 lec 1

7 – Six – memberd diheterocycles H | N N N O N | H Pyrimidine N | H Morpholine piperazine 8 – Six – membered triheterocycles 4 4 5 N 6 N 3 N 2 1 1, 3, 5 - Triazole 6 3 2 N S O 1 5 6 1, 4, 2 - Oxathiazine lec 1

B – Fused rings O coumarine γ 7 lec 1 O