SOME BASIC CONCEPT OF OPTICAL ISOMERISM:-
i. SN2 reaction proceeds with inversion of configuration
ii. SN1 reaction proceeds with racemization.
- Plane Polarized Light:-
Ordinary light have e.m. waves in in different directions (e.m→ electromagnetic). Thus such a beam of light which has vibration of EM waves only in one plane is called Plane Polarized Light.
- Optical Activity/Optically Active Substances:-
Such substances which can rotate the plane polarized light are called optically active substances.
And the property of a substance to rotate the plane polarized light light is called the Optical Activity.
A substance which rotates plane of polarized light towards right in clockwise direction is called Dextrorotary (+)
A substance which rotates the plane polarized light towards left is known as a Leavorotory substance (-)
- Optical Isomerism:-
The leavoratary (-)andDextrotatory (+) isomers of an aplocally active compound are called the optical isomers and phenomena is called as Optical Isomerism.
- Chiral Molecules:-
Objects or Molecules which are non superimposable on their mirror images are called Chiral Molecules and this properties is known as Chirality.
- Assymtrical Molecule:-
The molecule which have an Assymtric carbon atom (such that all the group or atom attached to carbon are different) is called Assymeterical molecule.
SOME BASIC CONCEPT OF OPTICAL ISOMERISM-II
Optical isomers which are the non superimpossible mirror images of each other are called as the Enantiomers
- Racemic Mixture:-
A mixture of the equal Amounts of the two enantiomers is called the Racemic Mixture or Racemic Modification.
The process of conversion of one entiomer (+ or -) into a Racemic Mixture is called Racemisation
If in a chemical reaction the special arrangement of bonds at an assymteric centre remains preserve than it would be known as Retention of Configuration.
SOME BASIC CONCEPT OF OPTICAL ISOMERISM-III
If the position of the substituent is get changed by 180o than it would be known as inversion of mixture
- Stereochemistry of SN2 Reaction:-
SN2 Reactions of optically active alkyl halide are always accompanied by inversion of configuration at the asymmetric centre.
- Stereochemistry of SN1 Reaction:-
In SN1 reaction if the alkyl halide is optically active then the product will be us a racemic mixture. Thus SN1reaction always accompanied Racemization.
i. Draw structures of possible enantiomers of 3 –methylpent – 1 –ene
Ans. The enantiomers of 3 – methylpent – l – ene are
ii. Identify chiral and achiral molecules in each of following pairs of compounds:-
a.(i) is the chiral molecule because it have assymetric carbon atom.
b.(I) molecule is chiral molecule because it have the assymetric carbon atom having all the four different substituents for C2.
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