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ABSTRACT:
In this survey, all types of cyclic compounds (aliphatic and aromatic) which containing one or more heteroatoms like (sulfur, nitrogen, oxygen, selenium,) various Membered Rings, methods of preparations, reactions, stability, strain of angle, some of applications, comparison of stability, nomenclature. Keyword:
KEYWORDS: Types of cycles, hetero atom, heteroaromatic, organometallic.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION:
Cyclic Compounds With Heteroatom
Compounds classified as heterocyclic probably constitute the largest and most varied family of organic compounds. After all, every carbocyclic compound, regardless of structure and functionality, may in principle be converted into a collection of heterocyclic analogs by replacing one or more of the ring carbon atoms with a different element. Even if we restrict our consideration to oxygen, nitrogen and sulfur (the most common heterocyclic elements), the permutations and combinations.
Hetero Aromatic Systems
This includes heteroannulenes, which comply with the HÜCKEL rule, i.e. which possess (4n + 2) **-electrons delocalized over the ring. The most important group of these compounds derives from annulene (benzene). They are known as heteroarenes, e.g.(( furan, thiophene, pyrrole, pyridine, and the pyrylium and thiinium ions)). As regards stability and reactivity, they can be compared to the correspondingbenzenoid.
The antiaromatic systems, i.e. systems possessing 4n delocalized electrons, e.g. oxepin, azepine, thiepin, azocine, and 1,3-diazocine, as well as the corresponding annulenes, are, by contrast, much less stable and very reactive.
The classification of heterocycles as heterocycloalkanes, heterocycloalkenes, heteroannulenes and Heteroaromatics allows an estimation of their stability and reactivity. In some cases, this can also beapplied to inorganic heterocycles(1-5). For instance, borazine, a colorless liquid, bp 55°C, is classifiedas a heteroaromatic system.
Heterocyclic Compounds A cyclic organic compound containing all carbon atoms in ring formation is referred to as a carbocyclic compound. If at least one atom other than carbon, forms a part of the ring system then it is designated as a heterocyclic compound(6-8).. Nitrogen, oxygen and sulfur are the most common heteroatoms.
Nomenclature:
Devising a systematic nomenclature system for heterocyclic compounds presented a formidable challenge, which has not been uniformly concluded. Many heterocycles, especially amines, were identified early on, and received trivial names which are still preferred. Some monocyclic compounds of this kind are shown in the following chart, with the common (trivial) name in bold and a systematic...