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1

### AIPMT 2010 Prelims

Which one of the following is most reactive towards electrophilic reagent?
A
B
C
D

## Explanation

+R effect of -OH group is greater than of -OCH3 group. That is why it is highly reactive towards electrophilic substitutions.
2

### AIPMT 2009

The IUPAC name of the compound having the formula
CH$$\equiv$$C$$-$$CH$$=$$CH2 is
A
1-butyne-3-ene
B
but-1-yne-3-ene
C
1-butene-3-yne
D
3-butene-1-yne.

## Explanation

Since the sum of numbers starting from either side of the carbon chain turns out to be the same, so lowest number is given to the C = C end.
3

### AIPMT 2008

The stability of carbanions in the following.

is in the order of
A
(iv) > (ii) > (iii) > (i)
B
(i) > (iii) > (ii) > (iv)
C
(i) > (ii) > (iii) > (iv)
D
(ii) > (iii) > (iv) > (i)

## Explanation

The carbonion which have more s-character will be more stable. Thus, the order of stability is :

(i) > (ii) > (iii) > (iv)
4

### AIPMT 2008

Which one of the following is most reactive towards electrophilic attack?
A
B
C
D

## Explanation

Groups like, –Cl and –NO2 shows –I effect. –I groups attached to the benzene ring decrease the electron density in the benzene ring and hence less reactive towards electrophilic attack.

On the other hand, –OH not only shows –I effect but also +M effect which predominates the –I character and electron density is increased in the benzene ring which facilitates electrophilic attack.

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Class 12