vimal - 1-2-2005 at 00:25
A question:
C=C + O3 ----> C=O + C=O after Zn/H2O
what else can we use instead of Zn/H2O?
Now: C=NH + O3 --- ?
do we get NH2OH ?
jizmaster - 1-2-2005 at 10:43
what do u mean, after Zn/H2O? no zinc is necessary.
vimal - 1-2-2005 at 17:31
No, Zinc/H2O is necessary. this is because, when ozone reacts, you first get an ozonide/malozonide. you need to reduce this to get a gem-diol, which
automatically gets converted to the C=O.
I have seen somewhere that (CH3)2S can also be used instead of Zn. is this a reducing agent? what does it get oxidised to?
chemoleo - 1-2-2005 at 17:43
Yes it is a weaker reducing agent, (CH3)2S would be oxidised further to the sulphoxide species, or even the methylsulphonic acid one (even though
(CH3)2S is already the oxidised species of CH3SH). I am surprised this would work instead of Zn/HCl, as this doesn't produce nascent hydrogen. Oh
well.
As to the NH2OH - I can see your reasoning - yet I doubt it, having read on it recently. Even H2O2 oxidises NH2OH to HNO3. I don't think
ozonolysis of imines would stop at the oxim step (subsequent hydrolysis), it'd probably carry on further to nitrous acid/nitric acid (or the
respective N-oxides).
Logically speaking, the product would be O=NH, which I believe is easily oxidised further.
Try to ozonise an imine, and see if you get nitrous gasses... the Fe test should tell ya.
[Edited on 2-2-2005 by chemoleo]
Synopsis - 1-2-2005 at 17:53
This is partly true. Indeed, an ozonide first form which rearranges to a more stable ozonide. The oxygen-oxygen bond of this ozonide needs to be
reduced, so to yield the free aldehydes/ketones upon hydrolysis (acetals and hemiacetals are involded, but no gem-diol is).
Most oxygen-oxygen bond reducers will yield the aldehydes/ketones. Most populars are Mg, Zn, Fe (usually in AcOH or aqueous HCl), Ph3P (liberates
Ph3PO) and Me2S (liberates DMSO).
NH2OH might be hard to make that way because you would have to use a selective oxygen-oxygen bond reducer which dosen't reduce nitrogen-oxygen
bond (or reduced them relatively slowly, if you ever get the desired product of the reaction). I would think there are easier way of making NH2OH from
imines. Unfortunatly I am unaware of how to actually do it at the time...
[Edited on 2-2-2005 by Synopsis]
jizmaster - 2-2-2005 at 02:39
ah right, i did it with KI, then oxidise the iodine with thiosulphate