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panziandi
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I added a solution of methyl nitrate in methanol to the reaction mixture, which was at a gentle reflux, addition of the methyl nitrate solution did
not seem to produce any additional heat.
There shouldn't have been any free hydroxide in solution, I used a stoichiometeric quantity which should have reacted completely to form phenoxide,
but I suppose hydrolysis could be an issue.
There was a large ppt, likely KNO3, and also there was significant product in the form of an emulsion when I poured it into NaOH solution. I lost
product in a messy workup. Perhaps pouring the solution into a larger volume of water would have been more suited. Also, just an idea but it may be
good to steam distil the products out of the reaction?
I would try methylating you hydroquinone in a methanol system using a 10% excess of methyl nitrate and refluxing for 4-6hrs. Try forming the phenoxide
by adding the phenol to a solution of KOH methanol. You should use a protective atmosphere for using polyhydroxy phenols in alkaline conditions since
they oxidise rapidly.
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smuv
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Quote: Originally posted by panziandi  |
I would try methylating you hydroquinone in a methanol system using a 10% excess of methyl nitrate and refluxing for 4-6hrs. Try forming the phenoxide
by adding the phenol to a solution of KOH methanol. You should use a protective atmosphere for using polyhydroxy phenols in alkaline conditions since
they oxidise rapidly.
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This was by and large already attempted (see prev page); just w/ more alkylating agent and a longer reflux; of course if Nitrogen was available it
would have been used. One mistake that was made though, was the 85% purity of KOH wasn't accounted for, therefore slightly less than 2eq of KOH were
used in reality.
I do agree though, a steam distillation would be the way to go for larger scale runs, assuming the product is volatile w/ steam.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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smuv
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A little late but...
I finally got around to taking an HNMR of the product from methylation of paracetamol. The product is indeed p-methoxy-acetanilide in good purity.
~7.4 - Ar-H (closest to amide) as well as N-H
7.24 - CHCl3
~6.8 - Ar-H
~3.8 - Acetyl protons
~2.1 Methyl
There is a slight impurity in the aromatic as well as some in the aliphatic regions however they are trivial. If someone wants to take a stab at
identifying the impurities, be my guest.
Spectra:
Full
Aromatic
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Nicodem
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All the peaks are consistent with the literature values except for the missing NH broad singlet at 7.14 ppm. There are some impurities signal at that
place... maybe it is so broad that it just flattened (if you would have integrated, maybe we could see if it partially hides beneath the AA'XX'
signals). The water signal is a bit far for CDCl3 where it is usually at about 1.5-1.6 ppm, but not extraordinarily far from where it is expected.
Anyway, thanks for confirming and sharing the results of your methylation via MeONO2. It was an interesting read.
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smuv
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Thanks.
I actually took a much better spectrum but was VERY rushed and only had time to print the aromatic region (and didn't save). In that spectrum the N-H
peak is much clearer. By the time I got around to running the sample again a lot of the CDCl3 evaporated, I didn't bother refilling and ran the
sample anyways, this is why the shim was so bad.
cleaner aromatic
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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