1
MCQ (Single Correct Answer)

NEET 2016 Phase 2

Which among the given molecules can exhibit tautomerism?
A
III only
B
Both I and III
C
Both I and II
D
Both II and III

Explanation

$$\alpha $$-hydrogen at bridge carbon never participates in tautomerism. Thus, only (III) exhibits tautomerism.
2
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

Consider the following compounds :

Hyperconjunction occurs in
A
III only
B
I and III
C
I only
D
II only

Explanation

Only structure (III) has $$\alpha $$-H in conjugation with free radical.

So, hyperconjugation is possible in III only.
3
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

In which of the following compounds, the C$$-$$Cl bond ionisation shall give most stable carbonium ion?
A
B
C
D

Explanation

Tertiary butyl chloride will give the most stable tertiary carbonium ion among the other given compounds due to hyperconjugation.
4
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

The enolic form of ethyl accetoacetate as shown below has
A
9 sigma bonds and 2 pi-bonds
B
9 sigma bonds and 1 pi-bond
C
18 sigma bonds and 2 pi-bonds
D
16 sigma bonds and 1 pi-bond.

Explanation

The given structure has 18$$\sigma $$ bonds and 2$$\pi $$ bonds.

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