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Why +I group increases bascitiy and delocalization of l.p. increases basicity..???

Why +I group increases bascitiy and delocalization of l.p. increases basicity..???

Grade:12

9 Answers

Neeti
571 Points
8 years ago
+I groups are those groups which delocalize the electron pair away from itself. Therefore a partial + charge +\delta appears on the group and -\delta on the carbon to which it is attached.Now when a +I group is attached to a main compound X, due to the electron ‘giving’ tendency of +I group, the -ve charge on main group X increases hence it’s basicity increases.
 
Likewise, delocalization of electrons over a particular group increases increases basicity
Akash Sharma
23 Points
8 years ago
I’m really srry..actually delocalisation of l.p. decreases bascity...please give reason for the same..
Neeti
571 Points
8 years ago
No No, i thought the same but then i thought that you must be talking about the group itself which is showing delocalization and that is also showing basicity.
see in case of delocalization, for example aniline, the lone pair on nitrogen gets delocalized and distributed all over benzene, hence the lone pair of nitrogen is now NOT available for donation hence it’s basic character decreases. :)
 please approve if you liked and understood my explanation and feel free to ask any other follow-up question. i’d be more than happy to help :)
Akash Sharma
23 Points
8 years ago
please can you explain in more precise way. I didnt get it.
Neeti
571 Points
8 years ago
absolutely. :) which part was not clear? the delocalization right?
see, nitrogen, oxygen, these atoms when in the form of a compound, have lone pairs. they can donate these lone pairs to form coordinate bond i’m sure you’re aware of that. In organic chemistry, they act as bases with the help of these lone pairs.
now, when NH2 is attached to benzene forming aniline (i’m unable to paste a diagram of the comppund) , the so the compound is basically C6H5NH2. this N also has lone pairs, but NH2- being a +R group, (resonance) gives away it’s lone pair to benzene ring and the lone pairs get “delocalized” over the entire benzene ring. Now since the lone pairs are delocalized over the ring, Nitrogen doesn’t have them anymore so it’s tendency to act as a base decrease. 
:)
 
 
Neeti
571 Points
8 years ago
Hence delocalization of electrons causes a decrease in basicity. because delocalization of the lone pair of nitrogen over the benzene ring causes a decrease in it’s basicity. 
if it’s still not clear you can ask the stuff you didn’t get :)
Akash Sharma
23 Points
8 years ago
Now i get it. Thanks again.
Neeti
571 Points
8 years ago
You’re welcome. :) you could approve the answers if you liked them :)
KING
46 Points
7 years ago
 
+I groups are those groups which delocalize the electron pair away from itself. Therefore a partial + charge +delta appears on the group and -delta on the carbon to which it is attached.Now when a +I group is attached to a main compound X, due to the electron ‘giving’ tendency of +I group, the -ve charge on main group X increases hence it’s basicity increases.
 

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