Organic Chemistry - 1

 

[1] In the benzyne mechanism of nucleophilic aromatic substitution reaction, benzyne act as:

(A) Nucleophile (B) Ambident nucleophile

(C) Electrophile ☑️ (D) Anchimeric assistance

[2] Smiles rearrangement is the example of :

(A) Intra-molecular rearrangement ☑️

(B) [2,3]-Sigmatropic rearrangement 

(C) Inter-molecular rearrangement 

(D) Nucleophilic aromatic cine substitution

[3] Hybridisation of each carbon atom present in benzyne reactive intermediate is:

(A) sp (B) sp2☑️ (C) sp3 (D) sp and sp2

[4] Some statement regarding the benzyne reactive intermediate given below, incorrect one is:

(A) It is aromatic in nature

(B) It is non-polar☑️ 

(C) It is 1,2-didehydrobenzene 

(D) It is neutral reactive intermediate 

[5] Which among the following rearrangement is based on [2,3]-Sigmatropic rearrangement ?

(A) Smiles rearrangement 

(B) Von- Ritcher rearrangement 

(C) Micheal rearrangement 

(D) Sommelet –Hauser rearrangement☑️

[6] Some statement regarding the nucleophilic aromatic substitution(SN2) reaction given below, incorrect one is:

(A) It is second order reaction 

(B) It involves fully stereo chemically inversion ☑️

(C) Rate = K[substrate][nucleophile] 

(D) reaction feasible only in one step 

[7] Some statements regarding nucleophilic aromatic substitution (SN1) reaction are given below, correct one is:

(A) Rate is double by increase conc. of nucleophile twice 

(B) Always racemic mixture as a product 

(C) Feasible with strong leaving group in substrate ☑️

(D) It is a second order of reaction 

[8] Replacement of Cl of chlorobenzene to phenol requires drastic conditions but chlorine of 2,4-dinitrochlorobenzene is readily replaced because:

(A) –NO2 makes ring electron rich at o- and p- position 

(B) –NO2 donates electron at m- position 

(C) –NO2 withdraws electron from o- and p- position ☑️

(D) –NO2 withdraws electron from m- position

[9] The addition of Br2 to Z – but- 2-ene gives:

(A) (R, R)- 2,3- dibromobutane only 

(B) (S, S)- 2,3- dibromobutane only

(C) (R, S)- 2,3- dibromobutane only 

(D) (R, R) + (S, S) -2,3- dibromo butane (50% : 50%) ☑️

[10] The type of sharp less asymmetric epoxidation reaction is:

(A) Regio-selective (B) Enantio-selective ☑️

(C) Regio-specific (D) Stereo-selective

[11] The number of π-electron present in benzyne reactive intermediate is:

(A) 8π (B) 6π☑️ (C) 7π (D) 10π

[12] Halo arenes does not undergoing nucleophilic aromatic substitution (SN1) because of:

(A)Shorter C – X bond 

(B) More polar C – X bond 

(C) Instability of phenyl cation 

(D) All the given above☑️

 

 

[13] The ambident nucleophiles are:

(A) – NHR, -NO2 

(B) –COOH, -CN 

(C) –NO2, -CN ☑️

(D) –NR2, -N = O

[14] The nucleophilic addition reaction involves carbanion to α-β unsaturated carbonyl compounds is:

(A) Micheal reaction ☑️

(B) Hansdiker reaction

(C) Stobbe reaction 

(D) Diels- Alder reaction

[15] The addition of Br2 to E – but- 2-ene gives:

(A) (R, R)- 2,3- dibromobutane only 

(B) (S, S)- 2,3- dibromobutane only

(C) (R, S)- 2,3- dibromobutane only ☑️

(D) (R, R) + (S, S) -2,3- dibromo butane (50% : 50%)