The formation of cyanohydrin from a ketone is an example of:

(1) electrophilic addition

(2) nucleophilic addition

(3) nucleophilic substitution

(4) electrophilic substitution

The compound which reacts with HBr obeying Markownikoff's rule is:

1. $C{H}_2=C{H}_2$   

2. 

3. 

4. 

If X is halogen the correct order for S_N2 reactivity is-

1. R₂CHX > R₃CX > RCH₂X

2. RCH₂X > R₃CX > R₂CHX

3. RCH2X > R₂CHX > R₃X

4. R₃CX > R₂CHX > RCH₂X

The electrophile. E^$\oplus$ attacks the benzene ring to generate the intermediate $\mathrm{\sigma }$- complex. Of the following which $\mathrm{\sigma }$- complex is of lowest energy?

1. 

2. 

3. 

4. 

Consider the following bromides:

the correct order of S_N1 reactivity is:

1. A>B>C

2. B>C>A

3. B>A>C

4. C>B>A

KI in acetone, undergoes S_N2 reaction with each of P, Q, R and S, the rates of the reaction vary as:

1. P > Q > R > S

2. S > P > R > Q

3. P > R > Q > S

4. R > P > S > Q

In an S_N1 reaction on chiral centres there is

1. 100% racemisation

2. inversion more than retention leading to partial racemisation

3. 100% retention

4. 100% inversion

Which of the following is an example of the elimination reaction?

1. Chlorination of methane

2. Dehydration of ethanol

3. Nitration of benzene

4. Hydroxylation of ethylene

The S_N2 mechanism for R-X + KOH (aq) $\to$ R-OH + KX follows with:

(1) 100% inversion

(2) 50% inversion

(3) 40% inversion

(4) 30% inversion

The elimination reaction among the following is:

1. CH₃CH₃+Cl₂$\to$CH₃CH₂Cl+ HCl

2. CH₃Cl+ KOH(aq.) $\to$CH₃OH +KCl

3. CH₂=CH₂ +Br₂ $\to$CH₂BrCH₂Br

4. C₂H₅Br+ KOH(alc.) $\to$C₂H₄ + KBr+H₂O