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resonance question

Discussion in 'DAT Discussions' started by joonkimdds, Dec 28, 2008.

  1. joonkimdds

    joonkimdds Senior Member
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    [​IMG][​IMG]

    I don't know how to solve these questions.
    Both of them are about resonance.
    For the first one, how do I know which one can stabilize?

    For the second one, what does it by an important resonance form?
    Does that mean which one is most stable? Like less charges(then I think D is correct), more electronegative atom with negative charge (A,B,C)?

    Answer for the first one is E and the second one is B.
     
  2. sciencegod

    sciencegod Super Member
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    the question is asking which one has a second resonadnce fomrm (somethng with resonance stabilizes it).
    question 2 is which one would be a good resonacne form. re3view resonacne if you dont know how to do this. the minus(2 electonsd) will move to make a bond bet c and h and that will force the electorns from the pi c=o bond to move to O.
     
  3. joonkimdds

    joonkimdds Senior Member
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    Let me guess. For both questions, the one with - charge should be bonded to the atom that is double bonded to something. Is that the right way to solve this type of problems?
     
  4. sciencegod

    sciencegod Super Member
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    yhea i think thats a a good way of looking at it.
     
  5. Sublimation

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    Look there is simple way to approach this. Just move electrons (i.e. something that is from a double bond or from a - charge oxygen or positively charged N) now try to move it anywhere without moving ANYTHING (cant move H or anything of that sort (only electrons). For the first one there are 2 possible answer choices, or i might be seeing things its 2AM lol and im not thinking very clearly. lol. Now for the first for B. The double bond that oyu see that connects the O to the C. You can move the electrons up and get a negative charge on the O and a positve cahrge on the C. This btw is very unstable and unhappy<<<<< NOTE One resonance structrure can be formed. THIS IS SUCH A POORLY WORDED QUESTION!!!! now for E. You have 2 possible resonance structures. First you can pull the negative charge down and form a double bond, and at the same time, move the double bond closest to the O to the carbon next to it to give a negative charge on the C, BTW happier then the friend without the electrons. C is electronegative (electron hogger). Then wat you can do for the second form is kick those 2 electrons down and push second double bond over the carbon that is meta( i think that means the one completely opposite it, i dont remember but correct me if im wrong) giving it a negative charge. Then u will end up with 2 resonance structures. Now this Q is REALLY STUPID. REALLY STUPID. Y? cuz it said which is stablized by resonance? Now B can be stabilized by resonance, but E does a better job of it, so thats a stupid and tricky one. I HOPE I DONT GET SOMETHING THAT STUPID ON MY DAT. I hope this helps. Gluck
     
  6. doc3232

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    The most important concept when it comes to resonance is that you must understand that there can hundreds of resonance structures. But only a few are good ones.

    KEY rules:
    Don't put charges on a carbon.

    Put charges on Oxygen and Nitrogen (neg for Oxygen and pos for Nitrogen)

    Charges in the allylic position from a double bond are not bad, charges in the benzylic positions are actually well-stabilized.

    Positive chages next to negative charges are very stable, but the one in the 2nd question is ridiculous because you can make a bond and get rid of both of them.
     

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