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azo
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The maufactures push it as a less toxic alternative but i don't agree with that .I think they are both as bad as each other,the glutaraldehyde does
not exist as a free aldehyde but as a pentahydrate.
regards azo
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safety first
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What about the hydrolysis of dimethoxymethane (methylal) in aqueous acid? I believe methylal can be found as the European substitute of DCM in paint
strippers. It also comes in those electronics cleaning sprays if I'm not mistaken. According to wiki it hydrolyzes back to formaldehyde and methanol
in the presence of the acid.
Just bought a can of paint stripper and planning to try this weekend. It shouldn't be very hard I'll just try to find a patent of sorts..
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weiming1998
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What's with all those complex tube setups? Oxidation of methanol with KMnO4 will do. Traces of formic acid will be formed, but not much, if you
control the amount of KMnO4 you put in. If your experiment won't allow any formic acid, then neutralize with a suitable hydroxide/carbonate that forms
a formate salt that's not very soluble. Then freeze and filter. Formaldehyde is more soluble in cold water than hot, while the solids are generally
more soluble in hot water than cold.
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Lambda-Eyde
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Quote: Originally posted by weiming1998  | | What's with all those complex tube setups? Oxidation of methanol with KMnO4 will do. Traces of formic acid will be formed, but not much, if you
control the amount of KMnO4 you put in. If your experiment won't allow any formic acid, then neutralize with a suitable hydroxide/carbonate that forms
a formate salt that's not very soluble. |
Have you tried this method of yours and analyzed the product? Do you have any references for this reaction?
This just in: 95,5 % of the world population lives outside the USA
You should really listen to ABBAPlease drop by our IRC channel: #sciencemadness @ irc.efnet.org
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weiming1998
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| Quote: Originally posted by Lambda-Eyde | | Quote: Originally posted by weiming1998 | | What's with all those complex tube setups? Oxidation of methanol with KMnO4 will do. Traces of formic acid will be formed, but not much, if you
control the amount of KMnO4 you put in. If your experiment won't allow any formic acid, then neutralize with a suitable hydroxide/carbonate that forms
a formate salt that's not very soluble. |
Have you tried this method of yours and analyzed the product? Do you have any references for this reaction? |
I have, just on the oxidation of ethanol instead of methanol, and since the two alcohols/aldehydes are very similar, it should work for methanol as
well. I haven't done any proper analysis based on testing solutions, but the smell of the acetaldehyde, the bubbling of the solution and the fact that
the smell isn't cleared by the addition of a base confirms the fact that it is an aldehyde.
References? http://en.wikipedia.org/wiki/Alcohol_oxidation
The end product of the oxidation is a carboxylic acid, but you see, the aldehyde is an intermediate product. If you use an excess of the alcohol, more
aldehydes are going to be produced instead of carboxylic acids.
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Lambda-Eyde
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| Quote: Originally posted by weiming1998 |
I have, just on the oxidation of ethanol instead of methanol, and since the two alcohols/aldehydes are very similar, it should work for methanol as
well. I haven't done any proper analysis based on testing solutions, but the smell of the acetaldehyde, the bubbling of the solution and the fact that
the smell isn't cleared by the addition of a base confirms the fact that it is an aldehyde. |
No, formaldehyde and acetaldehyde aren't as similar as you think. You can't generalize organic chemistry to such an extent as you do. Aldehydes
undergo several characteristic reactions, why haven't you performed any of them? Also, what was your yield? And do you know what happens to aldehydes
in the presence of strong bases?
Please, I asked for a reference for the oxidation of methanol to formaldehyde by permanganate, not a Wikipedia article about oxidation in general. I
know these reactions well, they are after all high school curriculum...
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You should really listen to ABBAPlease drop by our IRC channel: #sciencemadness @ irc.efnet.org
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weiming1998
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1, not all aldehydes are the same, I know that. But formaldehyde and acetaldehyde has similar chain lengths, and are all derived from monohydric
alcohols, so the properties of them should be fairly similar. Aldehydes react with strong bases, but I used a weak base to neutralize, like NaHCO3 or
Na2CO3, so there shouldn't be any reaction.
2, According to the Wikipedia page of alcohol oxidation, primary alcohols can be oxidized to either an aldehyde or a carboxylic acid. Methanol is a
primary alcohol and KMnO4 can act as the oxidizer in oxidizing primary alcohols. So why can't it be oxidized to an aldehyde? Even if I did not produce
any aldehyde in my experiment with the oxidation of ethanol, the article says that the oxidation of a primary alcohol to a carboxylic acid by
oxidation has to go by an intermediate stage of an aldehyde hydrate. So, according to the article, the oxidation of a primary alcohol to just an
aldehyde can be achieved by oxidizing the alcohol in an anhydrous environment, then bubble the aldehyde produced through water. It might not be
perfectly reliable, but it's still worth a try.
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testimento
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Dehydrogenation of methanol on copper or silver catalyst at high temperature is well known process. Would this work as well with platinum with iridium
or palladium catalyst? Because there is no risk of over-catalyzing the methanol due to absence of oxygen, the car catalytic converter would be ideal
for one step process due to it's massive surface area. It could be insulated and heated to red heat with propane burner and the methanol distilled
through it.
A short question for those who don't want to look into the concept: does platinum or palladium work in place of copper/silver in dehydrogenation
process?
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