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RyanJ

2 choices but which one?

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2 choices but which one?

 

Hi everyone!

 

I recently came upon a question in an old textbook I found in school.

 

It asked about the reacion of [ce]HBr[/ce] and [ce]C3H6[/ce]. I know the product of this reaction would be a haloalkane called bromopropane ([ce]C3H7Br[/ce]) but to my question - which would it be: 1-bromopropane or 2-bromopropane? I can find no good definate answer too this so I look to you for advice :D

 

Also as a little extra why would it form that one an not the other, is there some difference in the structure that makes one more preferable than the other?

 

Note: This is not a homework question its something I found during research and caught my interest!

 

Cheers,

 

Ryan Jones

 

Edit: Changed HCl too HBr - thanks for pointing that out insane_alien.

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I'll assume you meant HBr instead of HCl. it would be 2-bromopropane as the electrophile (H since it is delta +) will attach to the carbon with the most hydrogens on it.

 

Some 1-Bromopropane would be formed but it would be an significantly low proportion. search of regiospecific chemistry for more detailed explanations

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I'll assume you meant HBr instead of HCl. it would be 2-bromopropane as the electrophile (H since it is delta +) will attach to the carbon with the most hydrogens on it.

 

Some 1-Bromopropane would be formed but it would be an significantly low proportion. search of regiospecific chemistry for more detailed explanations

 

Ah - so in these kinds of reactions the Hydrogen will take preference too the Carbon with the most number of Hydrogens already attatched too it and thus force the halogen to be on the Carbon with the least number of Hydrogens?

 

Cheers' date='

 

Ryan Jones

 

[b']Edit:[/b] A little research turns out that its called Markovnikov's rule :)

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Yeah thats right. i couldn't remember how to spel Markovnikov so i gave up onit.

kept typing markinokovnikov.

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Yeah thats right. i couldn't remember how to spel Markovnikov so i gave up onit.

kept typing markinokovnikov.

 

I copied it from the alkenes link, I really will not ever be able to spell it - my spelling is bad enough for smaller words! Thanks for the help though - I like it when the rules are clearly defined, makes it easier to remember :)

 

Cheers,

 

Ryan Jones

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Please make sure that your HBr is pure i.e. HBR(l)

 

If HBr water is used , the product may be different

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Please make sure that your HBr is pure i.e. HBR(l)

 

If HBr water is used ' date=' the product may be different[/quote']

 

Yea I know, we finished learning about the different reaction types a few weeks back :)

 

Cheers,

 

Ryan Jones

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HBr(aq) would yield the halohydrin.

 

HBr(l) would have to be pretty cold and/or pressurized. better yet, you can use a different solvent.

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