Reduction of benzophenone to diphenylethanol

[Moogie]

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 haven't 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

 

[hermy]

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 :)

 

[Moogie]

It was methanol - my mistake. Thanks for the link