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Homework Help: Reduction of benzophenone to diphenylethanol

  1. Jun 9, 2010 #1
    Hi

    When you are reducing benzophenone to diphenylethanol you use 4 moles of sodium borohydride. I don't know how you would write this as an equation because I don't know what the sodium borohydride becomes. It has lost 4 hydride ions and is just with a sodium and boron. Also, you havent made the alcohol at this stage yet either - you have an intermediate with an O- species in it. YOu don't form the alchol until the acid work up step

    How would i write a balanced equation for this stage of the reaction?

    e.g. NaBH4 + 4Benzonphenone etc

    thanks
     
  2. jcsd
  3. Jun 23, 2010 #2
    Are you sure it is diphenyl'ethanol', not diphenyl'methanol' ?

    NaBH4 is used to reduce carbonyl group to alcohol, or in other words, it donates a hydride. The hydride bonds with the carbon, and oxygen gets a negative charge. Now, a new complex is formed. You can see the reaction here: http://www.chemguide.co.uk/organicprops/carbonyls/nabh4eq1.gif

    In the second stage of the reaction, water is added and the mixture is boiled to release the alcohol from the complex.
    http://www.chemguide.co.uk/organicprops/carbonyls/nabh4eq2.gif


    Source: http://www.chemguide.co.uk/organicprops/carbonyls/reduction.html

    Hope this helps :)
     
  4. Jun 23, 2010 #3
    It was methanol - my mistake. Thanks for the link
     
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