NEW
New Website Launch
Experience the best way to solve previous year questions with mock tests (very detailed analysis), bookmark your favourite questions, practice etc...
1

NEET 2016 Phase 1

MCQ (Single Correct Answer)
Which of the following biphenyls is optically active ?
A
B
C
D

Explanation

Ortho substituted biphenyls are optically active as both the rings are not in one plane and their mirror images are non-superimposable.
2

AIPMT 2015 Cancelled Paper

MCQ (Single Correct Answer)
The reaction of C6H5CH $$=$$ CHCH3 with HBr produces
A
B
C
D

Explanation

3

AIPMT 2015

MCQ (Single Correct Answer)
In an SN1 reaction on chiral centers, there is
A
inversion more than retention leading to partial racemisation
B
100% retention
C
100% inversion
D
100% racemisation

Explanation

In case of optically active alkyl halides, SN1 reaction is accompanied by racemisation. The carbocation formed in the slow step being sp2 hybridised is planar and attack of nucleophile may take place from either side resulting in a mixture of products, one having the same configuration and other having inverted configuration.

The isomer corresponding to inversion is present in slight excess because SN1 also depends upon the degree of shielding of the front side of the reacting carbon.
4

AIPMT 2015

MCQ (Single Correct Answer)
The possible stereo-structures of CH3CHOHCOOH, which are optically active, are called
A
atropisomers
B
enantiomers
C
mesomers
D
diastereomers

Explanation

They are enantiomers (non-superimposable mirror images)

Joint Entrance Examination

JEE Main JEE Advanced WB JEE

Graduate Aptitude Test in Engineering

GATE CSE GATE ECE GATE EE GATE ME GATE CE GATE PI GATE IN

Medical

NEET

CBSE

Class 12