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1

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
Homolytic fission of the following alkanes forms free radicals CH3 $$-$$ CH3, CH3 $$-$$ CH2 $$-$$ CH3, (CH3)2CH $$-$$ CH3, CH3 $$-$$ CH2 $$-$$CH(CH3)2.
Increasing order of stability of the radicals is
A
$$\eqalign{ & {\left( {C{H_3}} \right)_2}\mathop C\limits^ \bullet \, - \,C{H_2}C{H_3}\, < C{H_3}\, - \,\mathop C\limits^ \bullet H - \,C{H_3} \cr & < C{H_3}\, - \,\mathop C\limits^ \bullet {H_2}\, < {\left( {C{H_3}} \right)_3}\mathop C\limits^ \bullet \cr} $$
B
$$\eqalign{ & C{H_3}\, - \,\mathop C\limits^ \bullet {H_2}\, < \,C{H_3}\, - \,\mathop C\limits^ \bullet HH\, - \,C{H_3}\, < \cr & {\left( {C{H_3}} \right)_2}\mathop C\limits^ \bullet \, - \,C{H_2}\, - \,C{H_3}\, < \,{\left( {C{H_3}} \right)_3}\mathop C\limits^ \bullet \cr} $$
C
$$\eqalign{ & C{H_3} - \mathop C\limits^ \bullet {H_2} < C{H_3} - \mathop C\limits^ \bullet H - C{H_3} < \cr & {\left( {C{H_3}} \right)_3}\mathop C\limits^ \bullet \, < {\left( {C{H_3}} \right)_2}\mathop C\limits^ \bullet \, - C{H_2}C{H_3} \cr} $$
D
$$\eqalign{ & {\left( {C{H_3}} \right)_3}\mathop C\limits^ \bullet \, < {\left( {C{H_3}} \right)_2}\mathop C\limits^ \bullet \, - C{H_2}C{H_3} < \cr & C{H_3} - \mathop C\limits^ \bullet H - C{H_3} < C{H_3} - \mathop C\limits^ \bullet {H_2} \cr} $$

Explanation

Stability depends on number of hyperconjugative structure. More the number of hyperconjugative structure, the greater is the stability.
2

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour formed corresponds to which of the following formulae?
A
Fe3[Fe(CN)6]2
B
Fe4[Fe(CN)6]3
C
Fe4[Fe(CN)6]2
D
Fe3[Fe(CN)6]3

Explanation

The prussian blue colour is of Fe4 [Fe(CN)6]3 ferric ferrocyanide.
3

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
What is the hybridisation state of benzyl carbonium ion?

A
sp2
B
spd2
C
sp2d
D
sp3
4

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
Arrange the following in increasing order of stability
A
5 < 4 < 3 < 1< 2
B
4 < 5 < 3 < 1 < 2
C
1 < 5 < 4 < 3 < 2
D
5 < 4 < 3 < 2 < 1

Explanation

Greater the number of e donating alkyl groups (+I effect), greater will be the stability of carbocations.

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