WBJEE PYQs for Organic Chemistry with Solutions: Practice WBJEE Previous Year Questions

1.

The major product of the following reaction is $F_3C \rightarrow CH = CH_2 + HBr$

• F3C-----CH2----CH2Br
• F3C------CH(Br)------CH3
• 

• 

2.

Which one of the following formulae does not represent an organic compound?

• $C_{4} H_{10} O_{4}$
• $C_{4} H_{8} O_{4}$
• $C_{4} H_{7} ClO_{4}$
• $C_{4} H_{9} O_{4}$

3.

The correct order of relative stability of the given conformers of n-butane is

• II>I = III
• II>III>I
• II>I>III
• I = III>II

4.

The correct stability order of the following carbocations is : (I)H₂C⨁-CH=CH-CH₃, (II)⨁CH₂-CH=CH-BMe₂, (III)H₂C⨁-CH=CH-NMe₂, (IV)H₂C⨁-CH=CH-OMe

• II>I>III>IV
• III>I>II>IV
• III>IV>I>II
• IV>III>II>I

5.

The enol form in which ethyl-3-oxobutanoate exists is

6.

The product of the following hydrogenation reaction is:

7.

Which one of the following will show optical isomerism?

8.

How many monobrominated product(s) (including stereoisomers) would form in the free radical bromination of n-butane?

• 2
• 1
• 3
• 4

9.

The correct order of relative stability for the given free radical is:

• II>I>III
• II>III>I
• III>I>II
• III>II>I

10.

Ferric ion forms a Prussian blue precipitate due to the formation of

• $K_4[Fe(CN)_6]$
• $K_3[Fe(CN)_6]$
• $Fe(CNS)_3$
• $Fe_4[Fe(CN)_6]_3$

11.

The variation of pH during the titration of 0.5 N Na2CO3 against 0.5 N HCl is shown in the following graph:

The following table indicates the colour and pH range of different indicators:

Based on the given graph and table, which of the following statements are correct?a. The first point of inflection can be detected by cresolphthalein.b. The complete neutralisation can be detected by bromothymol blue.c. The second point of inflection can be detected by bromocresol red.d. The volume of HCl required for the first point of inflection is half of the volume of HCl required for the second point of inflection.

• (A) a, b and d
  
• (B) a, c and d
  
• (C) a, b and c
  
• (D) b, c and d
  

12.

What is the correct order of acidity of salicylic acid, 4-hydroxybenzoic acid, and 2,6-dihydroxybenzoic acid?

• 2, 6-dihydroxybenzoic acid>salicylic acid>4- hydroxybenzoic acid
• 2, 6-dihydroxybenzoic acid>4-hydroxybenzoic acid>salicylic acid
• Salicylic acid> 2, 6- dihydroxybenzoic acid >, 4 - hydroxybenzoic acid
• salicylic acid>4- hydroxybenzoic acid>2, 6- dihydroxybenzoic acid

13.

Hybridization of $C_2$ and $C_3$ of $H_3C - CH = C = CH - CH_3$ are

• $sp,sp^3$
• $sp^2, sp$
• $sp^2, sp^2$
• $sp, sp$

14.

Which of the following carbocations will be most stable ?

• $Ph_{3} C^{ +}$
• $CH_{3}-\overset {+}CH_{2}$
• $\left(CH_{3}\right)_{2} \overset{+} CH$
• $CH_{2} =CH-\overset{+} CH_{2}$

15.

The product of the following reaction is: