DrNoiZeZ
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4-chlorobutylacetate transesterification help
Hi
I am trying to find information about that transesterification but I could find none. Only a vage information on Rhodium "Re-etherification
with methanol in the presence of catalytic amounts of HCl or para-toluolsulfonic acid gives 4-clorobutanol-1 (bp 64-65°C @3mmHg) with yeld ~80%.
Reaction must be conducted at temperature not exeeding 50°C, otherwise the THF will form again. "
I did it with 149g of the acetate with 200 ml MeOH and 0,5g para-toluolsulfonic acid at 45Celsius for 4 hours but I am afraid that the reaction didnt
work at all, the product was fractionated and gave 130g of a liquid that has the same properties of the 4-chlorobutylacetate. I will make a
cromatography today and take the density and refraction index but I am pretty sure that it is the same substante because 130g is too much, I should
have something like 110g at top and the refracionation didnt show any change in the bp. Thanks for any help
[Edited on 29-8-2012 by DrNoiZeZ]
[Edited on 29-8-2012 by DrNoiZeZ]
[Edited on 29-8-2012 by DrNoiZeZ]
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Dr.Bob
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This makes little sense to me. You describe a transesterification, but then says "Re-etherification" later, then describe the BP of an alcohol, then
mention methanol, call it an acetate elsewhere, so it is not clear what you are trying to accomplish.
If you are trying to cleave the acetate off of 4-chlorobutylacetate with methanol to provide the 4-clorobutanol-1, I don;t see that acid will work
well, most transesterifications are done with basic conditions, like methoxide, but that might react with the 4-chloro group or reform the THF.
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DrNoiZeZ
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Hi, I am sorry if I didn`t make myself clear. For me the correct is transesterification but the quoted is re-etherification (I think he tried to say
re-esterification, who nows). The goal is to transfer the acetil from the 4-chlorobutanol to the methanol making methyl acetate and freeing
4-chlorobutanol as you well said and I think it is only possible with acidic conditions for the reasons you well pointed too.
Yesterday I run an HPLC and physical tests and as I suspect the reaction didn`t run. Now I am doing another with more acid (HCl) and 12 hours
refluxing, after that I intend to fracionate the methyl acetate first to push the equilibrium a little more.
Thanks
[Edited on 30-8-2012 by DrNoiZeZ]
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DrNoiZeZ
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Just for endind my former reply, after 12 h of refluxing 290 g of the ester with 10 ml HCl, gave the correct alchool after fracionating the methyl
acetate out with yield 78%. Now the physical properties (density, n20, solubillity and boiling point) and HPLC are correct.
[Edited on 4-9-2012 by DrNoiZeZ]
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