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Chemistry: Acetaminophen (paracetamol) > Phenacetin

  1. Apr 21, 2013 #1
    1. The problem statement, all variables and given/known data

    To convert acetaminophen to phenacetin it was added NaOH in ethanol and then Ethyl iodide.
    (Nucleophilic substitution). What would be the change in reaction velocity if insted of Ethyl iodide it was added 2-iodopropane (Isopropyl iodide)


    2. Relevant equations



    3. The attempt at a solution

    what affects the velocity of the reaction? Is it the stability of the reaction of NaOH with Acetaminophen? If it is, then the velocity is the same although I'm not sure..
     
  2. jcsd
  3. Apr 21, 2013 #2
    By velocity, the question asks to compare the rate of the two reactions. What do you think which nucleophilic substitution reaction takes place here? SN1 or SN2?
     
  4. Apr 21, 2013 #3
    SN1 in both, right? what do i Do next?
     
  5. Apr 21, 2013 #4
    Nope, think again.
     
  6. Apr 21, 2013 #5
    with Ethyl iodide the reaction is SN1 because the reaction is given in two steps: first neutralization and then nucleophic substitution.
    with 2-iodopropane i thought it was the same. is it as strong as Ethyl iodide as a nucleophyle?
     
  7. Apr 21, 2013 #6
    Check the structure of acetaminophen. What happens when NaOH is added to it? (Hint: There is an acidic hydrogen)
     
  8. Apr 21, 2013 #7
    the hydrogen of the hydroxyl group neutralizes the OH- from NaOH to form water. The oxygen in acetaminophen becomes negative and a good nuclephyle and attacks the iodine in Ethyl iodide or 2-iodopropane. Now that I think of, it is a SN2 reaction, at least with ethyl iodine. What next?
     
  9. Apr 21, 2013 #8
    Yes, you have that right. Now what happens when you use secondary alkyl halide instead of a primary one? Does the rate increase or decrease?
     
  10. Apr 21, 2013 #9
    the rate of a SN2 reaction depends on how stong the nucleophyl is, right? does it depend on the substrate, eletrophyl? Well, if it depends on the eletrophyl, with 2-iodopropane there is more stereochemical repulsion, so, is it slower with 2-iodopropane?
     
  11. Apr 21, 2013 #10
    Haven't you yet completed this topic? The rate depends on the substrate, the leaving group and the attacking nucleophile. It should be in your text about the rate dependence on the structure of substrate. We have the same leaving group and the attacking nucleophile in both the cases so we need not bother about that.
     
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