Cou
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I think hexane can be used as a Dean-Stark solvent alternative to benzene
http://www.sciencemadness.org/talk/viewthread.php?tid=154944
https://cpb-us-e1.wpmucdn.com/blogs.uoregon.edu/dist/1/8309/...
2nd link says hexane and water form an azeotrope boiling at 61.6 C and the vapor is 22.1% water.
One drawback is that salicylic acid is not soluble in hexane. For reactions with salicylic acid, you need benzene or toluene as the solvent.
Right now I am attempting a Dean-Stark fischer esterification with nonanoic acid, 1-pentanol (1.5 mol equiv), and hexane. I will update on how it goes
EDIT: I am very happy to say that it's working fine. Hexane and water are quickly forming layers in the dean-stark trap. Hexane is low boiling so it
reduces the amount of reactant escaping the flask
[Edited on 10-2-2020 by Cou]
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Boffis
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That's interesting, I have often wonder if hexane or cyclohexane could be used as a substitute for benzene in azeotropic esterifications. Good luck
Cou!
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Cou
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I was surprised at how fast the reaction finished, even at the low boiling temperature of hexane. All water was finished separating by 30 minutes, but
fischer esterification usually takes several hours.
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brubei
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hexane may lead to solubility issue but its low boiling point probably allow the use a second solvent with higher bp and polarity.
I'm French so excuse my language
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macckone
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n-butanol can also be used. Again it depends on reactant solubility.
It has non-zero solubility in water but works well for removing water with a dean stark trap.
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Boffis
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But won't the butanol also form an ester?
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Fery
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I used hexane succesfully when making esters (to remove water completely), there are some threads here in the forum. Also making anhydrous
allylalcohol from azeotrope (70%) worked well. Sometimes I used a fraction obtained by distilling medicinal petrolether, so no pure hexane but mixture
of isomers.
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Cou
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The nice thing about low boiling point of hexane is that it prevents reagents from escaping into the dean-stark trap, which sometimes messes up
separation of water.
If that becomes an issue, you can use a 3 neck flask and periodically add the organic layer in the Dean-stark trap back into the flask
[Edited on 10-2-2020 by Cou]
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Corrosive Joeseph
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Toluene.....?
/CJ
Being well adjusted to a sick society is no measure of one's mental health
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unionised
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I recall using isooctane once when measuring the water content of some greasy stuff.
Worked very nicely.
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Cou
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For some reactions, the boiling point of toluene is too high, which can cause reagents to boil over into the dean-stark trap and not be able to
return.
If both of your reagents are high boiling point, like salicylic acid and octyl alcohol, then yea toluene would be okay.
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macckone
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Yes it can, good point since this was for a fischer esterification.
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