ahlok2002
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THF in general synthesis.
THF (tetrahydrofuran) is very common solvent in chemical synthesis like esterification, hydrogenation...etc
i try to do esterification in lab with THF and compare with white mineral oil. the result is clearly difference. one can get the product within few
hours...and the latter can't get even days...
so any comment on th erole of THF on this reaction...and very please to hear more application on this THF..
thanks
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runlabrun
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You compared the solvent application on an esterification reaction between THF (a cyclic ether) and white mineral oil (mixed liquid hydrocarbons)???
right.... why?
THF is an excellent solvent for many reactions simply due to its structural nature, ethers in general are great solvents for many reactions however
are prone to high volitility and (especially for the case of diethyl ether) the formation of explosive peroxides. Now THF does form peroxides which
can be dangerous but not as easily as aliphatic ethers... THF bp 66oC whereas diethyl ether bp 33oC so it is applicable to many more reactions which
use higher temps. THF is also roughly as cost effective as diethyl ether and with these benefits gives rise to its wide use in industry.
-rlr
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DrP
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THF is a much better solvent than mineral oil. It's a much more polar molecule. Thus the reaction product are better dissolved and have more
'freedom' to move and meet the other molecules they are to react with - so they get into a reaction position quicker.
I'm not sure if viscosity has anything to do with it but on the same note you could imagine that in the lower viscosity THF the molecules do not take
so long to move arround to find the other reactants. In the more viscus oil, with longer chain molecules as the solvent, their could be hinderance
for the reactants and they will be slower to move arround into their reaction positions.
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runlabrun
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your reactants for the esterification would barely even be soluble in the mineral oil so no wonder the reaction didnt occur.... thats why i asked y
this was the comparitive sovlent to THF used... it would make more sense to compare water or alcohol to THF to see the difference in reaction rate and
yield.
But yes viscosity and polarity as mentioned play heavy roles in these type of reactions.
-rlr
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praseodym
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| Quote: | Originally posted by ahlok2002
...and very please to hear more application on this THF..
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http://www.orgsyn.org/orgsyn/chemname.asp?nameID=35996
This website shows you a list of preparations (organic syntheses) that involve THF.
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mick
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I do not think THF is a good sovent for esterification. Alcohols are good for that with a bit of base or acid. THF and diethyl ether are good
anhydrous solvents, THF being more polar and solvating (dissolving) better than ether.
mick
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ahlok2002
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| Quote: | Originally posted by mick
Alcohols are good for that with a bit of base or acid.
mick |
could it be the alcohol used reacts with the organic acid instead of the reactant?
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ahlok2002
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i would like to use white mineral oil instead of THF for this reaction mainly due to cost effective. we not need to recover the white mineral oil
after reaction ( if we apply in bulk production) compare with THF which is far more expensive than white mineral oil.
thanks praseodym for the link and to all who reply. thanks again.
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runlabrun
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yes but you have already established a known that esterification reactions dont work well in mineral oil -->
"i try to do esterification in lab with THF and compare with white mineral oil. the result is clearly difference. one can get the product within few
hours...and the latter can't get even days..."
How about u start by explaining the reaction your tryin to do? Simple esters can be made in water whereas more complex ones may require THF or alike
solvents to occur at all.
-rlr
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ahlok2002
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yes. certain people also advice me can try with hexene or touren. yet i haven't carry out the verification with these solvents.
the reaction is esterified the PIBSA (polyisobutylene succinate acid) with the polyalkanol amine. the medium i will consider is mineral oil, that was
suggested by one of the paper i got. maybe the PIBSA they use is lower in M.W, for my case, i use ~1000M.W. and the polyalkanol is ~110M.W.
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mick
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It depends on the final molecular weight, depends on the temperature. Azetrope the water off and measure it. Cyclohexane works instead of benzene.
Toluene or the xylenes also work. PTSA, para toluene sulphonic acid, was a good catalyst especially when dry
THF is a good solvent for a one to one esterification.
mick
[Edited on 15-1-2006 by mick]
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jon
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THF is more prone to peroxide formation than aliphatic ethers because the lone pairs on the oxygen are not sterically hindered like in diethyl ether
hence more reactive to the lone pairs of other oxygen atoms.
THF can make for some interesting pyrotechnics if your not aware of this.
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Drunkguy
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I would like to know to what extent THF is considered better than Et2O. I guess this is a bit of a dumb question actually.
-THF is more polar than Et2O
-[THF less suceptible to peroxide formation]
-THF higher bp in reactions involving reflux
I know that somebody said that these factors will lead to higher yields of product if one uses THF in lieu of Et2O.
To what extent is this true in a Grignard reaction for example?
[Edited on 22-1-2006 by Drunkguy]
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Drunkguy
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I also believed that THF is more prone to peroxide formation than Et2O and that i-Pr2O is extremely suceptible to it.
What I wrote in the above post is only reciting what I had read from others.
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jon
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In grignard reactions thf is it.
the reason is that oxygen in the ether forms complexes with the grignard reagent so thf having the more exposed oxygen lone pairs is the choice
solvent all I'm saying is watch out it forms explosive peroxides.
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