Q 1 :

Number of alkanes obtained on electrolysis of a mixture of CH3COONa and C2H5COONa is _________ .                  [2024]



(3)

     Kolbe's electrolysis of RCOO-Na+ gives R-R

     2RCOONa+2H2O→electrolysisR-R+2CO2+2NaOH+H2

     Thus electrolysis of mixture of CH3COONa and C2H5COONa gives three alkanes: CH3-CH3, C2H5-C2H5 and CH3-C2H5

 



Q 2 :

The incorrect statement regarding conformations of ethane is:                          [2024]

  • Ethane has infinite number of conformations.

     

  • The dihedral angle in staggered conformation is 60°.

     

  • Eclipsed conformation is the most stable conformation.

     

  • The conformations of ethane are inter-convertible to one-another.

     

(3)

 



Q 3 :

3-Methylhex-2-ene on reaction with HBr in presence of peroxide forms an addition product (A). The number of possible stereoisomers for ‘A’ is ______.           [2024]



(4)

Major product (A) has two chiral centres and from mechanism of this reaction it is clear that both R and S configurations are possible at both these chiral centres. Hence A has 22=4 stereoisomers.



Q 4 :

When sec-butylcyclohexane reacts with bromine in the presence of sunlight, the major product is :                [2025]

  •  

  •  

  •  

  •  

(4)

In free radical bromination of alkanes, that product is major which is formed by most stable free radical intermediate. Stability of free radicals is 3° > 2° > 1°. Out of two 3° carbons present in sec-butylcyclohexane, carbon I forms more stable free radical as it has more number of α H atoms.

 

 



Q 5 :

The maximum number of RBr producing 2-methylbutane by above sequence of reactions is ______. (Consider the structural isomers only)       [2025]

  • 4

     

  • 1

     

  • 3

     

  • 5

     

(1)

RBr→Mg+EtherR-Mg-Br→ H2ORH+Mg(OH)Br

Possible structural isomers of R–Br for RH = 2-methylbutane are obtained by placing Br at any one of the following four places:

 



Q 6 :

Propane molecule on chlorination under photochemical condition gives two di-chloro products, “x” and “y”. Amongst “x” and “y”, “x” is an optically active molecule. How many tri-chloro products (consider only structural isomers) will be obtained from “x” when it is further treated with chlorine under the photochemical condition.        [2025]

  • 3

     

  • 2

     

  • 5

     

  • 4

     

(1)

 



Q 7 :

Which of the following conformations will be the most stable?             [2023]

  •  

  •  

  •  

  •  

(1)

In the 1st option bulky Me groups are at anti position. It has least eclipsing as well as least van der-waal strain.



Q 8 :

All structures given below are of vitamin C. Most stable of them is:                    [2023]

  •  

  •  

  •  

  •  

(1)

 



Q 9 :

The correct sequence of reagents for the preparation of Q and R is:           [2023]

  • (i) Cr2O3,770K,20atm;  (ii) CrO2Cl2,H3O+;  (iii) NaOH;  (iv) H3O+

     

  • (i) Mo2O3,Δ;  (ii) CrO2Cl2,H3O+;  (iii) NaOH;  (iv) H3O+

     

  • (i) CrO2Cl2,H3O+;  (ii) Cr2O3,770K, 20atm;  (iii) NaOH;  (iv) H3O+

     

  • (i) KMnO4,OH-;  (ii) Mo2O3,Δ;  (iii) NaOH;  (iv) H3O+

     

(1)

 



Q 10 :

In the following reaction, ‘X’ is                [2023]

  • Cl–CH2–(CH2)4–CH2–Cl

     

  •  

  •  

  • CH3(CH2)4CH2Cl

     

(3)

This is isomerisation reaction of alkane.

 



Q 11 :

Number of bromo derivatives obtained on treating ethane with excess of Br2 in diffused sunlight is _______.         [2023]



(9)



Q 12 :

Identify A in the following reaction.                         [2026]

  •  

  •  

  •  

  •  

(2)



Q 13 :

Ph-CH=CH2→HBr(PhCOO)2Product

Consider the above reaction.

A. The reaction proceeds through a more stable radical intermediate.
B. The role of peroxide is to generate H• (Hydrogen radical).
C. During this reaction, benzene is formed as a byproduct.
D. 1–Bromo–2–phenylethane is formed as the minor product.
E. The same reaction in absence of peroxide proceeds via carbocation intermediate.

Identify the correct statements. Choose the correct answer from the options given below:    [2026]

  • A, B & D Only

     

  • A, C & E Only

     

  • C, D & E Only

     

  • A & E Only

     

(2)

Ph-CH=CH2→HBr(PhCOO)2Ph-CH2-CH2-Br

Anti Markovnikov addition

  • Reaction follows radical addition in presence of peroxide
  • In absence of peroxide follows carbocation mechanism
  • Benzene also formed



Q 14 :

Test Q

  •  

  • Enter Answer here

     

  • Enter Answer here

     

  • Enter Answer here

     

Select one or more options

Enter Answer here

 



Q 15 :

How many monocyclic structures are possible for C4H6 [Consider structural isomers only]



(4)



Q 16 :

n-Butane on monochlorination under photochemical condition gives an optically active compound "P". "P" on further chlorination gives dichloro compounds.

The number of dichloro compounds obtained (ignore stereoisomers) is:           [2026]

  • 3

     

  • 4

     

  • 5

     

  • 6

     

(2)

Attachment of Cl at four positions (marked in monochloro product) gives four different dichloro products.

[IMAGE 175]

 



Q 17 :

Given below are two statements:

Statement I: Methane can be prepared by decarboxylation of sodium ethanoate, Kolbe's electrolysis of sodium acetate and reaction of CH3MgBr with water.

Statement II: Methane cannot be prepared from unsaturated hydrocarbons and by Wurtz reaction.

In the light of the above statements, choose the correct answer from the options given below:                   [2026]

  • Both Statement I and Statement II are true

     

  • Both Statement I and Statement II are false

     

  • Statement I is true but Statement II is false

     

  • Statement I is false but Statement II is true

     

(4)

Statement I:

[IMAGE 176]

Statement II: Unsaturated hydrocarbons have minimum two carbons, hence methane cannot be prepared from them. Product of Wurtz reaction has minimum two carbon atoms.

[IMAGE 177]



Q 18 :

The compound (X) on

(i) on heating in the presence of anhydrous AlCl3 and HCl gas gives 2,4-dimethylpentane

(ii) aromatization gives toluene and

(iii) cyclisation gives methyl cyclohexane

The correct name of compound (X) is:                    [2026]

  • Hept-2-ene

     

  • Hept-1,3,5-triene

     

  • Heptane

     

  • Hept-2,4,6-triene

     

(3)

[IMAGE 178]

 



Q 19 :

The ratio of mass percentage (w/w) of C : H in a hydrocarbon is 12 : 1. It has two carbon atoms. The weight (in g) of CO2(g) formed when 3.38 g of this hydrocarbon is completely burnt in oxygen is:

(Given: Molar mass in g mol-1 C : 12, H : 1, O : 16)               [2026]

  • 5.68

     

  • 11.44

     

  • 22.74

     

  • 17.05

     

(2)

Let the hydrocarbon is C2Hx as it has two carbon atoms. Mass of C / Mass of H=(2×12)(x×1)=24x. As given in question :

24x=121, x=2. Thus the hydrocarbon is C2H2.

Moles of C2H2 burnt

=Given mass / Molar mass=(3.3826) mol=0.13 mol

2C2H2+5O2→4CO2+2H2O

As per reaction stoichiometry : Moles of CO2 formed

=2×moles of C2H2 burnt=2×0.13 mol=0.26 mol.

Mass of CO2 formed

=moles of CO2×molar mass of CO2

=0.26×44 g=11.44 g



Q 20 :

RMgI when treated with ice cold water liberated a gas which occupied 1.4 dm3/g at STP. The gas produced is further reacted with iodine in presence of HIO3 to give compound (X). Compound (X) in presence of Na and dry ether produced compound (Y). Molar mass of compound (Y) is _____ g mol-1. (Nearest integer)           [2026]



(30)

[IMAGE 197]

1.4 dm3 is volume of 1 g gas

22.4 dm3 is volume of 22.41.4 g gas=16 g gas

As 22.4 dm3 is volume of 1 mol gas, molar mass of gas is 16 g/mol i.e. the gas is methane(CH4).

CH4+I2→(Iodination)CH3I(X)+4HI

HIO3+5HI⟶3I2+3H2O

CH3I+2Na+ICH3→(Wurtz reaction)Dry etherCH3(Y)M = 30-CH3+2NaI



Q 21 :

One mole of an alkane (x) requires 8 mole oxygen for complete combustion. Sum of number of carbon and hydrogen atoms in the alkane (x) is _______.       [2026]



(17)

CnH2n+2+(3n+12)O2→nCO2+(n+1)H2O

As per reaction stoichiometry, (3n+12) mol of O2 require

1 mol of CnH2n+2. Thus 3n+12=8 or n=5. Thus the alkane is

C5H12. Sum of number of carbon atoms and hydrogen atoms

= 5+12=17



Q 22 :

An alkane (Y) requires 8 moles of oxygen for complete combustion and on chlorination with Cl2/hν, (Y) gives only one monochlorinated product (Z). The total number of primary carbon atoms in (Y) is _______ .                         [2026]



(4)

CnH2n+2+(3n+12)O2⟶nCO2+(n+1)H2O

As per given question, 3n+12=8, n=5. Thus the alkane is C5H12.

[IMAGE 198]

The alkane is neopentane and it has four primary carbon atoms.