Find the 12th Class Fsc Chemistry Online Preparation chapter 9 ( Aromatic Hydrocarbons)

Question # 1

Define two reaction which show that Benzene is an unsaturated hydrocarbons?

Ans 1: Benzene is reduced to cyclohexane on heating at high temperature with hydrocarbons in the presence if Pt in an acidic solvent or Ni at 200 Degree as a catalyst,This reaction show that benzene is Un-saturated compound.

Halogenation: Benzene reacts with chlorine and bromine in the presence of sunlight to give addition products ,hexechlorobenezene or hexebromobenzene.

Question # 2

Why benzene is less reactive than alkenes although it has three pi bonds in it?

Ans 1: Benzene is extraordinary stable molecule,This stability is due to the extensive delocalization of pi electron.The unhybridized orbital partially overlap to form a continue sheath of electron cloud,enveloping above and below the six carbon carbon sigma bonds of the ring,

Question # 3

What is resonance?

Ans 1: The possibility of different pairing schemes of valence electrons of atom is called resonance and the different thus arranged are called "Resonance Structure.".

Question # 4

What is meant by the terms:i) Aromatic ii) Oxidation

Ans 1: Aromatic:The term aromatic was derived from the Greek word aroma meaning fragrant and was used in organic chemistry for s special class of compounds.These compounds have low hydrogen to carbon ratio in their molecular formula and have a characteristic odour. These often produced by benzene or derivatives of benzene.
Ans 2: Oxidation:The addition of oxygen,removal of hydrogen or electrons is called oxidation.Oxidation process is carried out by some oxidizing agent like KMnO₄,K₂Cr₂O₇or V₂O₅etc.which can provide oxygen to a compound.

Question # 5

What is meant by directing group?

Ans 1: The groups which withdraw the electrons of the benzene ring towards themselves and reduce the availability to the electrophiles are called meta directing groups.The result is the decrease chemical reactivity of benzene,In their presence incoming electrophiles will prefer to attack on meta position nrather than orho and para position.

Question # 6

Write down nitration and sulphonation of benzene?

Ans 1: The introduction of NO₂group in benzene ring is called Nitration,.The nitration of benzene takes place when it is heated with a 1:1 mixture of conc.HNO₃and conc.Sulphuric at 50-55 degree acid reacts with nitrir acid to generate nitronium ion.

Question # 7

Why hydroxyl group in ortho and para directing?

Ans 1: Hydroxyl group release electron to the benzene ring .there by facilities the availability of electron to the electrophiles at ortho and para position.This result in the increase chemical reactivity of benzene ring towards electrophiles,The benzene ring can offer more than one position the new incoming group.

Question # 8

Predict major product of bromination of nitrobenzene.

Ans 1: m-bromonitrobenzene is the major product of bromination of nitrobenzene because nitro group on benzene is meta directing .

Question # 9

Define two reaction which confirm presence of three double bonds in benzene ring.

Ans 1: 1.Benzene is reduced to cyclohexane on heating at high temperature which hydrogen in the presence of Pt in an acidic solvent or Ni at 200 degree as a catalyst.
2.Benzene reacts with chlorine and bromine in the presence of sunlight to give addition products ,hexachlorobenzene or hexabromobenzene.

Question # 10

Define resonance energy?What is the resonance energy of benzene?

Ans 1: Benzene is more stable than the hypothetical 1,3,5-cyclohexatriene by 150.5 kj/mole.This difference between amount of heat is actually released and that calculated on the basis of the Kekule structure is called Resonance Energy Benzene shows the phenomenon of resonance which makes it more stable than others.In benzene electrons are delocalized making it a very stable molecule.The resonance energy of benzene is 150.5 kj/mole

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12th Class Fsc Chemistry Online Preparation chapter 9 ( Aromatic Hydrocarbons)

Online Short Questions For Chapter 9 "12th Class Chemistry Chapter 9 Short Questions Preparation "

Chemistry - 12th Class Chemistry Chapter 9 Short Questions Preparation

Define two reaction which show that Benzene is an unsaturated hydrocarbons?

Why benzene is less reactive than alkenes although it has three pi bonds in it?

What is resonance?

What is meant by the terms:i) Aromatic ii) Oxidation

What is meant by directing group?

Write down nitration and sulphonation of benzene?

Why hydroxyl group in ortho and para directing?

Predict major product of bromination of nitrobenzene.

Define two reaction which confirm presence of three double bonds in benzene ring.

Define resonance energy?What is the resonance energy of benzene?

Prepare Complete Set Wise Questions For Chapter 9 "12th Class Chemistry Chapter 9 Short Questions Preparation "

Set 1

Set 2

12th Class Chemistry Chapter 9 Short Questions Preparation - Set 1

Define two reaction which show that Benzene is an unsaturated hydrocarbons?

Why benzene is less reactive than alkenes although it has three pi bonds in it?

What is resonance?

What is meant by the terms:i) Aromatic ii) Oxidation

What is meant by directing group?

Write down nitration and sulphonation of benzene?

Why hydroxyl group in ortho and para directing?

Predict major product of bromination of nitrobenzene.

Define two reaction which confirm presence of three double bonds in benzene ring.

Define resonance energy?What is the resonance energy of benzene?

12th Class Chemistry Chapter 9 Short Questions Preparation - Set 2

What is the general pattern of reactivity of benzene towards electrophone?

What is Wurtz -Fritting reaction?

What happens when Acidified KMnO4is added to Methyl Benzene and Ethylbenzene?

Define two reaction which confirm presence of three double bonds in benzene ring.

What objective were raised on Kekule formula of Benzene?

What are aromatic hydrocarbons?Give two example.

Write down nitration and sulphonation of benzene?

Define two reaction which show that Benzene is an unsaturated hydrocarbons?

Define resonance energy?What is the resonance energy of benzene?

What are monocyclic and polycyclic aromatic Hydrocarbons?

12th Class Chemistry Chapter 9 Preparation

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What happens when Acidified KMnO₄is added to Methyl Benzene and Ethylbenzene?