Q: Which of the following carbocations is expected to be most stable?

−NO2 group exhibit -I effect and it decreases with increase in distance. In option (1) positive charge present on C-atom at maximum distance so -I effect reaching to it is minimum and stability is maximum.

Q: Consider the molecules CH4,NH3 and H2O. Which of the given statements is false?

All the molecules are sp3 hybridized and Bond angle of H2O is smaller than NH3.

Q: Which of the following biphenyls is optically active?

restricted rotation around bond is optically active (Non super imposable on its mirror image)

Q: In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1MH2SO4 . The percentage of nitrogen in the soil is :

∵M×V(ml)=mmol 10 m molH2SO4=20 m mol of NH3 [H2SO4+2NH3→(NH4)2SO4] 1 molNH3 contains 14 g nitrogen20×10−3 molNH3 contains 14×20×10−3 nitrogen0.75 g of sample contains% Nitrogen =0.7514×20×10−3×100=37.33%

Q: Some meta - directing substituents in aromatic substitution are given. Which one is most deactivating?

−NO2 is strong deactivating group.

Question 1

Paper chromatography is an example of:

Accepted Answer

Partition chromatography is based on the differential partitioning of components of a sample mixture between two phases – stationary phase and mobile phase. Most commonly it is used in paper chromatography which is a type of partition chromatography.

Question 2

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of:

Accepted Answer

More the number of ∝ - H atoms, more will be the hyperconjugation effect hence more will be the stability of carbocation.

Question 3

Elimination reaction of 2-Bromo-pentane to form pent-2-ene is(a) β - Elimination reaction(b) Follows Zaitsev rule(c) Dehydrohalogenation reaction(d) Dehydration reaction

Accepted Answer

Since β - hydrogen is abstracted it is β - elimination.Since more substituted alkene is formed, it follows zaitsev's rule.Since 'H' and 'Br' are removed, it is dehydrohalogenation.

Question 4

The number of sigma (σ) and pi (π) bonds in pent-3-en-1-yne is:

Accepted Answer

We have the structure:Number of σ bonds = 10and number of π bonds = 3

Question 5

Among the following, the reaction that proceeds through an electrophilic substitution, is:

Accepted Answer

Generation of electrophile:

Question 6

Which of the following carbocations is expected to be most stable?

Accepted Answer

−NO2​  group exhibit -I effect and it decreases with increase in distance. In option (1) positive charge present on C-atom at maximum distance so -I effect reaching to it is minimum and stability is maximum.

Question 7

Which of the following is correct with respect to – I effect of the substituents? (R = alkyl)

Accepted Answer

−1  effect increases on increasing electronegativity of atom. So, correct order of −1  effect is −NH2​<−OR<−F. ⋆ Most appropriate Answer is option (3), however option (2) may also be correct answer.

Question 8

Consider the molecules CH4​,NH3​ and H2​O. Which of the given statements is false?

Accepted Answer

All the molecules are sp3 hybridized and Bond angle of H2​O is smaller than NH3​.

Question 9

The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is:

Accepted Answer

CH3​−CH3​

Question 10

Which of the following biphenyls is optically active?

Accepted Answer

restricted rotation around bond is optically active (Non super imposable on its mirror image)

Question 11

In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g  of sample neutralized 10 mL  of 1MH2​SO4​ . The percentage of nitrogen in the soil is :

Accepted Answer

∵M×V(ml)=mmol 10 m molH2​SO4​=20 m mol  of NH3​ [H2​SO4​+2NH3​→(NH4​)2​SO4​] 1 molNH3​  contains 14  g nitrogen20×10−3 molNH3​  contains 14×20×10−3 nitrogen0.75 g  of sample contains%  Nitrogen =0.7514×20×10−3​×100=37.33%

Question 12

Some meta - directing substituents in aromatic substitution are given. Which one is most deactivating?

Accepted Answer

−NO2​  is strong deactivating group.

Question 13

Which one is the correct order of acidity?

Accepted Answer

Correct order is

Question 14

The correct statement regarding electrophile is:

Accepted Answer

Fact.

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Solutions for Organic Chemistry-Some Basic Principles and Techniques Important Questions

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