1
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.
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

In Duma's method for estimation of nitrogen, 0.25 g of an organic compound gave 40 mL of nitrogen collected at 300 K temperature and 725 mm pressure. If the aqueous tension at 300 K is 25 mm, the percentage of nitrogen in the compound is
A
16.75
B
15.76
C
17.36
D
18.20

Explanation

Wt. of organic substance = 0.25 g

V1 = 40 mL, T1 = 300 K

P1 = 725 – 25 = 700 mm of Hg

P2 = 760 mm of Hg (at STP)

T2 = 273 K

$${{{P_1}{V_1}} \over {{T_1}}} = {{{P_2}{V_2}} \over {{T_2}}}$$

V2 = $${{700 \times 40 \times 273} \over {300 \times 760}}$$ = 33.52 mL

Percentage of nitrogen

= $${{28 \times 33.52 \times 100} \over {22400 \times 0.25}}$$

= 16.76%

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