IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

tarinbansal

Answers-

1-A

2-B

3-B

4-B,D

5-A

Explanations-

1- The reason to this ques is quite clear. As Cl cant make the compound 3 degree by changing its position, it means methyl group must hav migrated and hence they are chain isomers.

2-The answer is B becoz of - Hydrogen bonding between -OH and =O , Hyperconjugation as due to restricted rotation, the alkene has 2 alpha H which means 2 hyperconjugative structures and also due to resonance between OH, = , =O.

Some people hav written only resonance, they hav got +1 for the reason not +2 as they hav not explained the complete reason.

3-Many of U hav given the reason that due to resonance in the molecule, negative charge comes at B so it is the answer. As far as I know, lone pair on N does not participate in resonance as it is not in the plane of pi bonds. Rest of the molecule shows resonance similar to benzene.

I don't think that due to resonance negative charge comes at B. Those who hav said this, must hav taken lone pairs of N in resonance also. PLZ anyone who thinks that negative charge comes at B due to resonance, post the resonance structures here.

Reason- Just break a double bond in + and - and at the position of - , put the electrophile and resonate the + throughout the compound.

U will find that when Electrophile is at A and C, on resonating +, positive charge comes on N which is very unstable and when electrophile is at B, no positive charge comes at N due to resonance so it is most stable.

4-Almost all of U got it right. It is an exceptional case in which the last unpaired electron in 3D shell flies off to last orbital of 4p due to strong field nature of ammonia. SO it is paramagnetic and dsp2.

5- The best ques of the test and no one has given the 100% correct answer.

The mechanism applied in this ques is called NGP( Neighboring group participation).

Just luk at the figure. As all the C are sp3 hybridised, the chain cannot be a straight chain and its structure is something like I hav shown in the figure.

Now, S has lone pairs which help OH- from KOH to repel Cl and Cl leaves very easily.

U will be surprised to know that the reaction in case of option A is 10000 times faster than that of option B.

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