some orgo chem questions

[Contach]

---

Members don't see this ad.

can someone explain some things to me please:

1) i understand taht most substituted carbocations and most substituted radicals are most stable. What about carbanions?

2) is a phenyl substiuent electron donating or electron withdrawing?

3) Why are more substituted alkenes more stable than less substituted alkenes?

4) oh. and why isn't aniline basic? (its phenyl-NH2)

merci beacoup

 

[nixon13]

1) i understand taht most substituted carbocations and most substituted radicals are most stable. What about carbanions?

2) is a phenyl substiuent electron donating or electron withdrawing?

3) Why are more substituted alkenes more stable than less substituted alkenes?

4) oh. and why isn't aniline basic? (its phenyl-NH2)

1. Carbanion stability is opposite of carbocations and radicals.
2. Good question, im not sure.
3. Dont wanna look it up.
4. If the substituent on the benzene ring is electron withdrawing, then the ring becomes more acidic. If its electron donating then the ring becomes more basic. NH2 is an electron donating group so aniline WOULD be basic.

 

[GCT]

can someone explain some things to me please:

1) i understand taht most substituted carbocations and most substituted radicals are most stable. What about carbanions?

2) is a phenyl substiuent electron donating or electron withdrawing?

3) Why are more substituted alkenes more stable than less substituted alkenes?

4) oh. and why isn't aniline basic? (its phenyl-NH2)

merci beacoup

1) It depends on the surrounding environment of the ion ; donating groups such as alkyl groups stabilize carbocations and withdrawing groups stabilize carboanions .

2) Phenyl groups can declocalize electrons on an attached group however it can serve as a carbon source as electron donating with respect to inductive effects .

3) Hyperconjugation

http://books.google.com/books?id=yV...X&oi=book_result&resnum=2&ct=result#PPT163,M1

4) The Lewis base electrons on the nitrogen are delocalized.

 

[211183]

1)

4) The Lewis base electrons on the nitrogen are delocalized.

can someone explain that? i am not sure i get the concept..

 

[doc3232]

For aniline: Overall concept is that the ring can take them through resonance.

 

[doc3232]

I have never heard of a phenyl group...I have no idea whether it would be donating or withdrawing...All I can say is that it will heavily stabilize due to all the new resonance.


And for the first question: Think of the carbocation and the radical as having too few electrons so electron donating groups COULD stabilize.
As for the carboanion, think the opposite: There are two electrons that can go no where, alkyl groups donating electrons won't stabilize.

 

[Retimo]

For aniline: Overall concept is that the ring can take them through resonance.

2) yea, what they said.. mostly e donating for inductive reasons

3) word, hyperconjugation, but also inductive effects as well, if I remember. Look up Zaitsev's Rule for a reminder

4) props to doc3232.. check out this page if you're still having trouble visualizing it.. they have some helpful diagrams if you scroll down a tad

http://www.chemguide.co.uk/organicprops/aniline/amine.html