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    2-bromo-2-methylpropane,C4H9Br can be used to produce methylpropene,C4H8. 2-bromo-methylpropane reacts with sodium ethoxide, NaOC2H5 to produce ethanol,C2H5OH and sodium bromide , NaBr along with methylpropene. using the relative formula masses of the reactants and products,
    work out the atom economy for this reaction.

    What I did was i worked out the rfm of the desired product which was methylpropene,C4H8 = 56
    Then I wrote down the equation

    So C4H9Br + NaOC2H5 --> C2H5OH + NaBr + C4H8

    Then I added all the rfm's of all the products (C2H5OH + NaBr + C4H8)
    So ((12x2) + 5 +16+1) + (23+79.9) + ((12x4)+8) = 204.9

    So
    atom economy = molecular mass of desired product / sum of molecular masses of all products x100

    (56/204.9)x 100 = 27.3304.. So 27.3% 3s.f

    Unfortunately my answer is wrong and the right answer is 41% ??

    Why is that?
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    (Original post by FluffyCherry)
    2-bromo-2-methylpropane,C4H9Br can be used to produce methylpropene,C4H8. 2-bromo-methylpropane reacts with sodium ethoxide, NaOC2H5 to produce ethanol,C2H5OH and sodium bromide , NaBr along with methylpropene. using the relative formula masses of the reactants and products,
    work out the atom economy for this reaction.

    What I did was i worked out the rfm of the desired product which was methylpropene,C4H8 = 56
    Then I wrote down the equation b

    So C4H9Br + NaOC2H5 --> C2H5OH + NaBr + C4H8

    Then I added all the rfm's of all the products (C2H5OH + NaBr + C4H8)
    So ((12x2) + 5 +16+1) + (23+79.9) + ((12x4)+8) = 204.9

    So
    atom economy = molecular mass of desired product / sum of molecular masses of all products x100

    (56/204.9)x 100 = 27.3304.. So 27.3% 3s.f

    Unfortunately my answer is wrong and the right answer is 41% ??

    Why is that?
    I do hate this atom economy stuff. There seems to be no consistency to how things are calculated.

    To get 41% the maths is

    Mr[C4H8]/Mr[C4H9Br]
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    (Original post by TeachChemistry)
    I do hate this atom economy stuff. There seems to be no consistency to how things are calculated.

    To get 41% the maths is

    Mr[C4H8]/Mr[C4H9Br]
    This is really confusing, how am I supposed to know whether to use the formula of atom economy or do what you just did?:erm:

    Besides why would they include the reaction of 2-bromo-methylpropane with sodium ethoxide ??? :lolwut:
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    (Original post by FluffyCherry)
    This is really confusing, how am I supposed to know whether to use the formula of atom economy or do what you just did?:erm:

    Besides why would they include the reaction of 2-bromo-methylpropane with sodium ethoxide ??? :lolwut:
    I agree with you. I'd have worked out the atom economy in the exact same way that you did.
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    True back of an envelope mechanism.

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    (Original post by TeachChemistry)
    I agree with you. I'd have worked out the atom economy in the exact same way that you did.
    (Original post by TeachChemistry)
    True back of an envelope mechanism.

    Name:  image.jpeg
Views: 125
Size:  168.1 KB
    (Original post by TeachChemistry)
    I do hate this atom economy stuff. There seems to be no consistency to how things are calculated.

    To get 41% the maths is

    Mr[C4H8]/Mr[C4H9Br]
    I see, thanks anyway
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    Where is the Q from? Who says that the answer is 41%?

    Whoever they are, they are wrong, it is 27.3%, even Wikipedia agrees!
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    (Original post by Pigster)
    Where is the Q from? Who says that the answer is 41%?

    Whoever they are, they are wrong, it is 27.3%, even Wikipedia agrees!
    The question is from the Edexcel AS chemistry book, and I've got the answers to the book with me. You see I think you're right cos I've noticed some mistakes in the answers to student book itself in other questions. :facepalm:
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    How very dare you : ) Of course I'm right.

    (also we are right, it is a mistake)
 
 
 
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