August 24, 2019

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- ANNULENES


ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- ANNULENES

**Annulenes are the completely conjugated monocyclic hydrocarbons containing an even number of carbon atoms. They have the general formula CnHn (when n is an even number) or Cn.Hn+1 (when n is an odd number) 

**The first 3 members of the series, (4]-, [6]-, and [8]-annulene but you must have used their name as 1,3- cyclobutadiene, benzene and 1,3,5,7- cyclooctatetraene. 

**Annulenes could be aromatic, anti aromatic or non-aromatic.

#[4] Annulene: anti-aromatic 

#[6] Annulene: aromatic 

#[81 Annulene: non-aromatic

#[10] Annulene: non-aromatic 

#[12] Annulene anti-aromatic 

#[14] Annulene: anti-aromatic.

#[18] Annulene: aromatic. 

**The following bridgehead [10] annulenes are aromatic: 

#9,10 methane [10] annulene 

#9,10 oxa [10] annulerne 

#9,10 aza [10] annulene 

**Preparation of [14] annulene, [18] annulene and 9,10-methane [10] annulene from simple and easily available molecules.