October 21, 2017

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- HYPER-CONJUGATION


ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- HYPER-CONJUGATION

**The delocalization of sigma electrons or lone pair of electrons into adjacent π-orbital or p-orbital is called hyper conjugation. 

**It takes place because of overlapping of sigma-bonding orbital or the orbital containing a lone pair with an adjacent untitled p-orbital. It is also called as "no bond resonance" or "Baker-Nathan effect" 

**It explains stability of alkenes, carbocations and free radicals. 

**The dipole moment of the molecules and bond length is greatly affected due to hyperconjugation since the contributing structures show considerable polarity and change in bond order. 

**Hyper conjugation also explains the reactivity & orientation of electrophilic substitution on alky1 substituted benzene ring. 

**The overall tendency of anomeric substituents to favour an axial position is called Anomeric effect. For example. the alpha-methy1 glucoside is more stable than the Beta

**For alpha-halo alkenes, the delocalization of electrons takes place towards the halogen group through hyperconjugative mechanism because of electron withdrawing nature of halogen. It is known as reverse hyperconjugation.

 
ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- HYPER-CONJUGATION