Ol ---> Oic

[YT2095]

branching of from posts #3 and #4 in http://www.scienceforums.net/forums/showthread.php?t=17097

so as to not go off topic.

 

I`m interested in organic oxidation mentioned, specificaly the conversion of R-OH to R-COOH (ols to oics) with KMnO4.

I`m sure most are familiar with the Glycerine (1,2,3 propan triol) and KMnO4 reaction.

what is it that makes it actualy Catch fire though? is there any stage where Propanoic acid is made before it catches fire, and can this reaction be slowed down (maybe dilluted in water?) and this acid extracted?

secondly KMnO4 and sugar (C12H22O11) react when wetted with water giving off alot of heat, can this also be slowed down and something usefull other than Carbon be extracted?

thirdly, when oxidising Ethanol with KMnO4 wouldn`t there be a small trace of ethyl ethanoate ester produced at some point?

[Ilja]

To your third question:

 

You mean a reaction of ethanol with the acetylic acid that accure when u oxidise it ?

 

I dont think there will be one , maybe there could be one if u work with conentrate H2SO4 as catalyst.Because you can also oxidise Ethanol in appearence of OH- , and if u want to create ethyl ethanoate ester you will need an acidic medium with concentrate H2SO4 which will also bind the resulting h2o of the reaction of ethanol with acetylic acid.

 

By the way you can make Propanoic acid like this => C2H4 + CO + H2

 

The reason why the glycerin catchs fire is that at some point the glycerin forms some product (Acrolein dont know the english word for it maybe its the same ) , an unsaturated carbon-hydrogen compound which starts to burn, actually thats what i think im not sure though.

 

 

hope i could help you abit

[Yggdrasil]

I believe the problem you are having is that you are using polyhydroxylated substrates for your reactions. Since oxidation of an alcohol to a ketone or acid is exothermic, oxidizing a compound with multiple OH groups can produce a lot of heat, which will lead to overoxidation and thermal decomposition of most of your product. So, the solution would be to either use a weaker reducing agent or try oxidizing other substrates.

 

If you're interested in oxidizing sugars, you can oxidize glucose (or other aldoses or 2-ketoses) to an aldonic acid in basic conditions by treatment with Br₂/CaCO₃/H₂O, Ag₂O or tollen's reagent (Ag(NH₃)₂⁺). These reagents will convert the aldehyde of an aldose to a carboxylic acid. It works to some extent on 2-ketoses (e.g. fructose) since they isomerize to aldoses in basic conditions. Unfortunately, sucrose (table sugar) is not a reducing sugar, so it cannot be oxidized to an aldonic acid.

 

Periodic acid can also be used to oxidize sugars.

[YT2095]

Thanx both

 

in the case of propan 1 2 3 triol, being a polyhydroxylate, surely it should still work in an aqueos soln, but would need more oxidiser than a monohydroxylate obviously, perhaps if it were kept very cold too?

 

I see your point about the sugar or rather Sucrose, it would be less than ideal on a OH to C count, and could only really leave carbon and water, well it`s certainly given me a few more experiment ideas for my list of things to do over the cold winter months!