1

### 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.
2

### 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. 3

### 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.
4

### 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%