jmneissa - 9-11-2010 at 19:50
Hey guys so I am investigating alkyl disulphides in my lab however today I did the reaction for the first time and got an unexpected result. My
reaction was normal at first then started out gassing a white smoke. The reaction mechanism is shown below:
RSCN + KOH = (RS)2 + ?
This mixture is refluxed with ethanol. The mixture starts as a whitish yellow powder and then becomes a dark red liquid which from literature is to be
expected. My question is though what is the byproduct(s) from this? Is it KCN + H2O2 or KOCN etc.... We shut down the reaction upon production of the
white smoke for fear that this was hydrogen cyanide or some other highly poisonous gas and were not prepared to deal with it so aired on the side of
caution. Thanks!
madscientist - 9-11-2010 at 21:28
What was the temperature and pH of the reaction when the white smoke was observed? Was it produced in large quantities? What were the amounts of
reactants used?
jmneissa - 10-11-2010 at 05:59
The Reaction temperature was at 80 degrees C the pH was not measured and all compounds were pure so it should have been basic due tot the addition of
the potassium hydroxide to the ethanol solution. The amount of reactants used were the calculated amounts without any excess. That was 12.13 g of RSCN
and 1.67g of KOH in about 20 ml of ethanol (95% denatured with methanol)
[Edited on 10-11-2010 by jmneissa]
MagicJigPipe - 11-11-2010 at 10:32
Out of curiosity, what was the alkyl group (R)? Why are you leaving that info out?
Does anyone know the reaction mechanism of this?
Is it based off of abstraction of a proton from the alkyl group forming the carbanion?
Also, how could HCN be formed with a significant source of protons like an acid?
[Edited on 11-11-2010 by MagicJigPipe]
jmneissa - 13-11-2010 at 20:19
That was my thought that HCN could not form because it was a basic solution. The alkyl group is a fluorocarbon I was just leaving it out since the
size of the fluorocarbon is different for each test to study the effects under pressure so I was more asking in general what the reaction mechanism
was.
MagicJigPipe - 13-11-2010 at 21:28
I think the fact that it's an fluorocarbon makes quite a difference. In this way the mechanism probably could not be through the abstraction of a
proton, because there would be no protons. Is it ALL fluorine (perfluoro)? I'm just curious as to the mechanism because I couldn't find it online.
jmneissa - 15-11-2010 at 11:36
Well no it was a perfluorohexyl ethyl molecule. My guess though was that since the molecule is treated as a group then shouldn't it just form KOCN
because that is what we thought would be produced.