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Topic: Is this reaction is possible?  (Read 447 times)

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Offline maximh

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Is this reaction is possible?
« on: June 15, 2020, 05:04:53 AM »
Hello,
I'm trying to get a specific product, will this reaction work? (this was a question in my exam):



Online Babcock_Hall

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Re: Is this reaction is possible?
« Reply #1 on: June 15, 2020, 06:37:55 AM »
What are your thoughts?

Offline maximh

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Re: Is this reaction is possible?
« Reply #2 on: June 15, 2020, 06:40:28 AM »
that is possible

Offline rolnor

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Re: Is this reaction is possible?
« Reply #3 on: June 15, 2020, 07:08:20 AM »
What about the first step, how will you control that you only get one HBr adding and not two? Also, is there any risk for side-reactions, you have strong acid and two reactive groups?

Offline maximh

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Re: Is this reaction is possible?
« Reply #4 on: June 15, 2020, 09:18:18 AM »
What about the first step, how will you control that you only get one HBr adding and not two? Also, is there any risk for side-reactions, you have strong acid and two reactive groups?

maybe use only one equivalent of hbr?

Offline rolnor

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Re: Is this reaction is possible?
« Reply #5 on: June 15, 2020, 12:29:12 PM »
But the mono-brominated compound will react as fast as the non-brominated, how will you get this selectivity?

Offline Enthalpy

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Re: Is this reaction is possible?
« Reply #6 on: June 15, 2020, 05:34:10 PM »
But the mono-brominated compound will react as fast as the non-brominated, how will you get this selectivity?

Could the sought mono-alcohol leave the reaction medium as soon as it's formed? Apparently not usual in a lab, but with adequate setup maybe. React among gases, let the mono-alcohol rain down but choosing the temperature pressure.  The prediction software Mpbpvp imagines that the mono-alcohol boils at 41K warmer than the diene under 1atm, and at +25°C its vapour pressure is 20 times smaller.

Bromine makes a much smaller difference. So the process would begin with water addition, which can be stopped at the mono-alcohol, and continue with HBr addition.

Would that be conceivable?

Online Babcock_Hall

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Re: Is this reaction is possible?
« Reply #7 on: June 16, 2020, 08:44:35 AM »
Enthalpy wrote, "Bromine makes a much smaller difference. So the process would begin with water addition, which can be stopped at the mono-alcohol, and continue with HBr addition.

Would that be conceivable?"
I see a potential problem with two reactions possible for HBr.  @OP, what do you think?

Offline Enthalpy

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Re: Is this reaction is possible?
« Reply #8 on: June 17, 2020, 04:15:22 PM »
OK, probably a bad attempt. Unless some special conditions lead to HBr addition.

Offline AWK

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Re: Is this reaction is possible?
« Reply #9 on: June 26, 2020, 06:11:22 AM »
Have you considered the reverse order of reaction?.
The yield of dibromo derivative can be significantly increased by exchange of OH for Br by exchange using PBr3
« Last Edit: June 26, 2020, 06:22:43 AM by AWK »
AWK

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