woelen
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Methane sulfonic acid as replacement for H2SO4?
Last week, the company laboratoriumdiscounter.nl added methane sulfonic acid, CH3SO2(OH), to their set of own brand chemicals. It can be ordered for a
very good price, at 70% concentration. I just ordered 2 liters.
I have no practical experience with this acid at all, but it is quite strong, non-oxidizing and also not strongly coordinating. So, it seems like a
good general acid for many experiments. In many cases, it might be a good replacement of moderately concentrated H2SO4, which is hard to obtain in the
EU and if it is available, only at max. 15% concentration. Conc. HCl is not always suitable, due to the coordination properties of chloride ion in
many cases and this also becomes harder to obtain. HNO3 is not available anymore in the EU. So, having an affordable alternative, which can be ordered
without hassle, would be very nice.
Do others have any experience with this acid?
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Texium
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The only time I’ve used it was as the solvent for a Skraup reaction, which was originally developed to run in sulfuric acid, and it worked quite
well in that application. In many cases it may indeed be a suitable substitute for sulfuric acid.
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Hexabromobenzene
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This is an expensive alternative. Sulfuric acid can be obtained by electrolysis of gypsum in a bag of fabric. You can even not buy electrodes but make
them from charcoal and sugar or flour
Some will say: what is the point of synthesizing acids and solvents? But I would not want to start this existential conversation
[Edited on 24-6-2024 by Hexabromobenzene]
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woelen
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I do not agree with you. Most people will not start experimenting at all, if they first need to have a big mess with all kinds of low-grade OTC
materials from the hardware store, before they have a few ml of useable acid. Making acids of good purity from stuff like gypsum, or other low-grade
OTC stuff is not easy at all and most starters will be put off before they even start.
I now ordered two liters of methanesulfonic acid at 70% concentration, lab grade quality, for appr. 30 euros. I think that this is a very good
alternative to messing around with hardware store stuff to get a few ml of impure acid. I can understand that some people like the challenge of making
useful chemicals from low-grade OTC stuff, but that only is for the really determined people, with good engineering skills and some practical
experience. Availability of useful chemicals for starters will lead to more people doing experiments, and some of these people then become really
determined people.
[Edited on 25-6-24 by woelen]
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Fery
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I would like to use the acid for condensation/cyclisation reactions. Is the 30% water content OK or should I use pure acid without water? I have
plenty of conc. H2SO4, 85% H3PO4 and P4O10 to make polyphosphoric acid, but some reactions have better yields and purer product when using
methanesulphonic acid. I found such synthesis here, read also the comments, they are very useful:
https://orgprepdaily.wordpress.com/2009/11/10/8-bromoquinoli...
[Edited on 25-6-2024 by Fery]
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woelen
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Laboratoriumdiscounter.nl also can sell pure methanesulfonic acid, but the anhydrous acid is very expensive. It is a little over 100 euros per liter.
Maybe it is possible to boil off most of the 30% water? If I receive the acid, then I'll try that. If the acid decomposes, what would be the
decomposition products?
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chornedsnorkack
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Quote: Originally posted by woelen  | | Laboratoriumdiscounter.nl also can sell pure methanesulfonic acid, but the anhydrous acid is very expensive. It is a little over 100 euros per liter.
Maybe it is possible to boil off most of the 30% water? If I receive the acid, then I'll try that. If the acid decomposes, what would be the
decomposition products? |
Of stability:
https://link.springer.com/article/10.1007/s40831-022-00641-6
I did find links about decomposition. From what I recall, the prevalent path was
CH3SO2OH->CH3OH+SO2
followed by
CH3SO2OH+CH3OH->CH3SO2OCH3+H2O
A methylating agent, note. The temperature range seems to be 225...250 C.
Even if mesylic acid did not pyrolyze at boiling (triflic acid does not), since mesylic acid is a strong acid, mere boiling would be expected to yield
a high boiling azeotrope. Such azeotropes could be broken down by pressure swings, or by freezing - but that´s extra complexity.
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