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Old Nov 1st 2011, 07:54 PM   #1
bennettb6
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Orgo: Prepare compound B from A

My chem exam had this question and I couldn't figure out how to put it together.

Propose a method to prepare compound B from compound A

Both compounds are benzene with an ethane attached, only compound A has an OH attached to the first branch of the ethane and compound B has it attached to the end (second branch) of the ethane.

If someone could tell me how to properly name these compounds that'd be cool too
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Old Nov 2nd 2011, 05:49 AM   #2
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To be honest, I'm getting rusty with those

Well, the first is called 1-phenyl ethanol and the second is 2-phenyl ethanol.

The only thing I'm able to think of now is first to dehydrate the alcohol using concentrated H2SO4 which gives us phenyl ethene, and from there, maybe some way to hydrate the second branch instead of the first somehow...

That is, if I understood the compounds well.
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Old Nov 2nd 2011, 08:27 AM   #3
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So a friend of mine explained it today, but I don't know how much she knows what she's talking about, can anyone confirm this?

She said you can add H+ in the presence of heat and h2o to dehydrate the alcohol, and then hydrobromate it with HBr in the presence of H2O2 and OH because that will add an OH group on the end because that process has anti markovnikov regiochemistry.

What do you think?
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Old Nov 2nd 2011, 08:34 AM   #4
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Yes, reacting the alcohol with water vapour gives the same product as with concentrated sulfuric acid, so you now get phenyl ethene.

And as for the other part, I'm not familiar with Markovnikov's reactions at all

*Just looked it up and if that really is an anti Markovnikov rule reaction, then it works perfectly!

You get 2-phenyl monobromoethane first, the halogen which then gets substituted by OH (nucleophilic substitution).
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