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Strong nucleophile or no?

Discussion in 'DAT Discussions' started by DentalLonghorn2014, Aug 20, 2015.

  1. DentalLonghorn2014

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    Hey y'all,

    So, a phosphorus with 3 R groups and N with 3 R groups. Chad said that P can be a strong base but in a Q&A they said a P with 3 R groups is not a good nucleophile due to it being too "fat". Also, what about N?

    Thank you!!
     
  2. clutchfans

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    Even though N is smaller than P, NR3 is still going to be pretty bulky making it a poor nucleophile.
     
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  3. DentalLonghorn2014

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    I see. Thank you.
     
  4. orgoman22

    orgoman22 DAT DESTROYER
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    Phosphorus is among our VERY BEST nucleophiles. We use them in many reactions such as the Wittig and Gilbert reaction. Even a sterically hindered nucleophile works great.....the Phosphorus -atom distance is reasonably long, the electrons are very loosely held. Although, not as common as S, N, or O nucleophiles,,,,,,these reagents are AMAZING !!!! I have read many books on Phosphorus Chemistry, and count it as one of my favorite elements !!!!

    Hope this helps

    Dr. Romano

    Here are a few examples.......

    sdn ex.gif
     
  5. DentalLonghorn2014

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    Thank you Dr. Romano. What about N with 3 R groups? Would that be a weak nucleophile but decent base?
     
  6. orgoman22

    orgoman22 DAT DESTROYER
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    A nitrogen with 3 R groups is usually the Kiss of Death when it comes to nucleophilicity,,,,,,just too damn big ! As far as basicity goes,,,,,we usually see an increase in its strength. For reasons still debated, steric effects dont count as heavily when basicity is concerned, likely because we are capturing a simple hydrogen ion. Interestingly, quinuclidine is a tertiary amine, that is a decent nucleophile. Can you tell me why ?

    Here is a picture of the compound......
    dental LH.jpg
     
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  7. DentalLonghorn2014

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    Is it because there's less hinderance? This may sound dumb but there's more "free " space in the front with the nitrogen than the back?
     

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