for upcoming experiments I need to make some terephthaloyl chloride. Because I want some backup if they don't work as expected, I need around 100g to
200g. The first thing I did was making a lot of crude terephthalic acid from bottles.
Now for the follow up procedures. I found this thread here: http://www.sciencemadness.org/talk/viewthread.php?tid=63196
I his first post Waffles used refluxing with thionyl chloride. This route can be cancelled out since I cant get or make it. Later he mentioned that
sulfur chloride can be used as well. Is there any procedure for this? However I don't prefer this nasty stuff.
I did further research and found this really interesting paper (large link):
Especially example 2 is awaking my curiosity. As the authors mentioned earlier other esters like ethyl or propyl could be used equally well.
I would definitely go for diethylterepthalate due to certain advantages like higher boiling point since this is fairly high temperature (220°C).
What I am interested in: Has anyone experience with these kind of reactions? Are they practical, where are the dangers? Is there any data about vapour
pressures at 220°C for the chloride or the ethyl ester (do I need condensors)? How to purify the ethyl ester or the chloride? what are good solvents
for crystallisation procedures?
And very important: How tho esterify the terephthalic acid? My first attempt using a bit of h2so4 catalyst and dried etoh under long reflux failed!
I really hope to get some input before I dive into, thanks in advance!
[Edited on 6-2-2018 by subskune]LearnedAmateur - 7-2-2018 at 08:04
If you want to make any acyl chloride, you’ll need to be working with nasty reagents no matter what since it’s a chlorination reaction. IMO,
phosphorus chlorides (PCl3 or PCl5) may be a safer option, especially the latter which is a solid at RT, but other members will have more experience
than I here.
I did a couple of reactions involving acyl chlorides in school, and I can say that they’re more practical than the safer routes to esterification
because they don’t exist in an equilibrium. One was the synthesis of nylon (can’t remember which type exactly but it was definitely a spontaneous
diamine + diacyl chloride reaction) and the other was esterification using acetyl chloride, can’t remember the alcohol used. These have the benefits
of proceeding automatically - as long as the temperature is kept low, the generated HCl (ROH + R’COCl -> HCl + ROOCR’) won’t do much in the
way of hydrolysis, especially considering that the HCl can potentially leave the reaction as a gas, driving the equilibrium.
If you’re making the ester from a carboxylic acid and alcohol with strong acid as a catalyst, then you’ll have to play with the equilibrium by
utilising the boiling points of either the reactants or products. As I’m sure you’re aware, the formula for ‘classical’ esterification is
RCOOH + R’OH <-(H+)-> RCOOR’ + H2O; exploiting Le Chatelier’s principle, if the ester boils at a higher point than water (which it does in
the case of terephthalic esters), then the water can be distilled off as it forms, leaving the acid and ester in the distillation flask - the presence
of acid doesn’t matter if there isn’t any water. If it boils at a lower point, the ester can be distilled off, likely resulting in a mixture of
ester, alcohol, and/or carboxylic acid, but this depends on the particular combination thus may require fractionating. If you’re lucky, the ester
may not be soluble in water at all, where it will form a separate layer and is manually decanted.DJF90 - 7-2-2018 at 08:51
I'd have a crack at using this methodology, if you have mechanical stirring:
then the water can be distilled off as it forms, leaving the acid and ester in the distillation flask
Unfortunately the ethanol has an even lower bp and will leave first with very poor azeotrope so I have to reflux. The resulting ester is not soluble
in water.
@DJF90
This method seems to work for aromatic acids as indicated in the paper. I just need to find an appropriate solvent for the diethylterepthalat. They
used a lot of sulfuric so maybe thats crucial, I'll try.
While the ester might be doable I am really curious about the chlorination of the ester at elevated temperature.
Unfortunately the ethanol has an even lower bp and will leave first with very poor azeotrope so I have to reflux. The resulting ester is not soluble
in water.
Best thing I can think of is to keep adding ethanol to the reaction flask or to employ a desiccating agent - sodium sulphate will probably be your
best bet here. You should observe better yields either way, just as long as you employ some way to keep the reactants at a far higher concentration
than the water.DJF90 - 7-2-2018 at 13:05
You won't be able to add sodium sulfate to the reaction mixture as a dessicant due to the presence of sulfuric acid, which will give you sodium
bisulfate in situ.
As the comments on that blog post suggest (I'm "Dan" by the way...), its about 0.6 eq. sulfuric acid, which isn't a large amount. I recall my first
esterification as a process chemist - we used 3.7 eq. sulfuric acid and approximately 10 vol. of methanol to convert a substituted phenylacetic acid
to its methyl ester on several 100g scale, with a conversion of >95mol%. The sulfuric acid also acts as a dessicant in this case, sequestering
water from the esterification equilibrium.
As for the chlorination at elevated temperature, it seems feasible, but if its the same patent I'm thinking of (my phone browser won't open your link
for some reason) then you'll notice its a relatively large amount of chlorine used (approx 5 eq. iIRC).byko3y - 8-2-2018 at 15:38
Yo, folks, this thread is about making dicarboxyl dichloride, not even about using it. Having two electron-withdrawing groups those acyl chlorides
have properties similar to those of oxalyl chloride. As of today I know no easily accessible and safe method for making dicarboxyl dichloride - you
can't make it the way you can make acetyl chloride or propionyl chloride, you need only strongest chlorinating agents.subskune - 9-2-2018 at 03:59
Quote:
As of today I know no easily accessible and safe method for making dicarboxyl dichloride - you can't make it the way you can make acetyl chloride or
propionyl chloride
I know it, the first problem is that even the "nasty procedures" can't be done since I can't get the reactants. Thats why I came up with the patent
paper. That's the only way I know I could do.
I've never done it yet so my goal is to get some tips or hints to get it going from someone who knows something about this (maybe).byko3y - 9-2-2018 at 08:04
subskune, there's a lot of similar patents and you might already know triphosgene and diphosgene production method which is a free-radical exhaustive
chlorination of esters. But nobody actually tried the procedures here, there might be some problems with ring chlorination, chances are small though
due to strong deactivation of the ring.
