1

### AIPMT 2010 Mains

The IUPAC name of the compound
CH3CH$=$CHC$\equiv$CH is
A
pent-4-yn-2-ene
B
pent-3-en-1-yne
C
pent-2-en-4-yne
D
pent-1-yn-3-ene

## Explanation

If a molecule contains both carbon-carbon double or triple bonds, those two are treated as per in seeking the lowest number combination. However, if the sum of numbers turns out to be the same starting from either of the carbon chain, then lowest number is given to the C = C double bond.
2

### 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.
3

### 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.
4

### 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)