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Topic: 2-Chlorobutane to 1-butanol and 1-Butanol to 2-Bromobutane  (Read 18088 times)

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Offline CaptTeemo

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2-Chlorobutane to 1-butanol and 1-Butanol to 2-Bromobutane
« on: February 06, 2013, 10:08:14 PM »
As the title says, if I wanted to make 1-butanol from 2-chlorobutane, would heated E2 with t-Butoxide then Oxymercuration/Demercuration be a good pathway? The issue I have, mentioned again below, is the + charge being wandering between the 2nd and 3rd carbon, giving me mixed products.

For the reverse, except with Bromine, i.e., 1-Butanol to 2-Bromobutane, is a reaction with HBr viable? I'm thinking formation of a carbocation delocalized to the secondary carbon, but then, again, nothing is stopping the charge from delocalizing to the 3rd carbon as well so this doesn't seem that viable as I'd get a mix of 2- and 3-Bromobutane.

btw, is there anyway to perform a trans reduction of alkynes to alkenes? i know that for syn u can go lindlar and H2, but not sure about trans because other methods seem to force their way down to alkanes.

edit: wait, I'm dumb, symmetry should mean that 2- and 3- butanol are the same molecule... right?

Offline souro10

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Re: 2-Chlorobutane to 1-butanol and 1-Butanol to 2-Bromobutane
« Reply #1 on: February 07, 2013, 01:23:48 AM »
1-butanol from 2-chlorobutane- if you use strong hindered bases like t-Butoxide or LDA , first the base will pull a proton from the 1-carbon of 2-chlorobutane and then Cl- ion shall be expelled- via E2 mechanism. I don't understand why the + charge should be delocalized between 2-carbon and 3-carbon!

In the above E2 reaction, you get 1-butene as the major product. If you want to produce 1-butanol , you need an -OH group at the primary end. Oxymercuration demercuration will give you Markownikov regioselectivity. You need anti-markonikov here. So I'd say go for Hydroboration and then oxidation with alkaline solution of hydrogen peroxide to get 1- Butanol.

If you want to get 2-Bromobutane from 1-Butanol, acid catalyzed dehydration of 1-Butanol will produce 2-Butene as the major product ( first product is 1-Butene, but reaction does not stop at that stage. It again captures a proton to form a secondary cation and then loses electron according Setzeff rule ). From 2-Butene you want to go to 2-Bromobutane? Why not simply add HBr? If you used concentrated HBr as the dehydrating agent, your product will be 2-Bromobutane.

For trans reduction of alkynes to alkenes you can use Sodium or Lithium in liquid ammonia- Birch Reduction.

2- and 3-butanol do mean the same molecule.

Offline CaptTeemo

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Re: 2-Chlorobutane to 1-butanol and 1-Butanol to 2-Bromobutane
« Reply #2 on: February 07, 2013, 03:54:49 AM »
Oh my I can't believe I confused OxyHg/DeHg's selectivity with that of Hydroboration! Thank you so much for reminding me!
Thank you for all your *delete me* :) Much appreciated.

edit: so for the second reaction, why wouldn't adding HBr alone work? wait, that'd give 1-bromobutane.

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