NEET and AIPMT NEET Chemistry Hydrocarbons MCQ Questions Solved


Which is the most suitable reagent among the following to distinguish compound (III) from rest of the compounds?                                                                                                 

I. CH3-CC-CH3

II. CH3-CH2-CH2-CH3

III. CH3-CH2-CCH

IV. CH3-CH=CH2

(a) Br2/CCl4                     (b) Br2/CH3COOH

(c)Alk.KMnO4                   (d) Ammonical AgNO3

(d) It may be noted that only the terminal alkynes react with ammonical silver nitrate. Therefore, this reaction can be used to distinguish between 1-alkynes and others such as alkane, alkenes and non-terminal alkynes.

     CH3-CH2-CCH + 2[Ag(NH3)2]NO3 CH3CH2CCAg

                                                                         white ppt.

Difficulty Level:

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Which of the following reagents will be able to distinguish between 1-butyne and 2-butyne?       

(a) NaNH2            (b) HCl             (c) O2                 (d) Br2

(a) NaNH2 is used to distinguish between 1-butyne and 2-butyne.

    CH3CH2CCHNaNH2CH3CH2CCNa  + 1/2 H2

     CH3-CC-H NaNH2No reaction

Difficulty Level:

  • 62%
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A compound is treated with NaNH2 to give sodium salt. Identify the compound.                      

(a) C2H2                  (b) C6H6

(c) C2H6                   (d) C2H4

(a) Sodamide is strong base, attract the more acidic hydrogen and gives sodium salt

  H-CC-H + NaNH2 H-CC-Na+    +  1/2 H2

                                    Sodium ethynide

Difficulty Level:

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The product of the reaction between 

 +(CH3)3COH ?

(1)             (2)        (3)           (4) 

(1) Grignard reagent with any compound containing acid hydrogen forms a hydrocarbon.

Difficulty Level:

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The reaction of toluene with Cl2 in the presence of FeCl3 gives 'X' and reaction in presence of presence of light gives 'Y'. Thus 'X' and 'Y' are                                            

(a) X= benzal chloride, Y=o-chlorotoluene

(b) X=m-chlorotoluene, Y=p-chlorotoluene

(c) X=o and p-chlorotoluene, Y= trichloromethyl benzene

(d) X= benzyl hloride, Y=m-chlorotoluene

(c) In the presence of halogen carrier, electrophilic substitution occurs, while in the presence of sunlight, substitution occurs at the side chain.

Difficulty Level:

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What products are formed when the following compound is treated with Br2 in the presence of FeBr3?                                                                            

(c) CH3 is an o/p-directing group, thus electrophilic substitution reaction of toluene.

        

Difficulty Level:

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When chlorine is passed through propene at 400°C, which of the following is formed?            

(a) PVC                         (b) Allyl chloride  

(c) Nickel chloride          (d) 1,2-dichloro ethane

(b) When chlorine gas is reacted with propene at high temperature (400°C), then substitution takes place in place of addition reaction. Hence, allyl chloride is formed.

 CH3-CH=CH2 + Cl2 400°CC|H2-CH=CH2 + HCl          Cl                                   

Difficulty Level:

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In Friedel-Craft's alkylation, besides AlCl3 the other reactants are                                     

(a) C6H6 + NH2

(b) C6H6 + CH4

(c) C6H6 + CH3Cl

(d) C6H6 + CH3COCl

(c) Friedel-Craft's alkylation When benzene reacts with alkyl halide in presence of anhy. AlCl3, toluene is obtained. It is called Friedel-Craft's alkylation. Friedel-Craft's reaction is type of electrophilic substitution.

  C6H6 + CH3Cl Anhy.AlCl3C6H5CH3 + HCl

                                      Toluene

Difficulty Level:

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Benzene reacts with n-propyl chloride in the presence of anhydrous AlCl3 to give                    

(a) 3-propyl-1-chlorobenzene

(b) n-propyl benzene

(c) no reaction

(d) iso-propyl benzene

(d) Electrophilic substitution reaction of Benzene ring.

 

Difficulty Level:

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When acetylene is passed through dil.H2SO4 in presence of HgSO4, the compound formed is

(a) ether                           (b) ketone

(c) acetic acid                    (d) acetaldehyde

(d) Hydration of alkyne, 

CHCH + H2OHg2+/H+TautomerisationCH3-CHO

Difficulty Level:

  • 9%
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