[AlphaScent]

I was given the task of preparing an Oxime.  I followed my procedure and the formation does not seem to be complete.  Is it as simple as adding more hydroxyl amine*HCl and base?

I am doing the reaction now.  Want your thoughts..

Cheers

[clarkstill]

You could try, if you aren't already, removing the H2O by azeotroping?  Without your full reaction conditions it's pretty hard to know what to suggest...

[AlphaScent]

I apologize.

Here is what happened:

Added to a 50 mL, 3-neck RB flask was 26.0 mmol benzaldehyde, 32.5 mmol hydroxylamine*HCl.  6.54 g of H2O was then added and vigorously stirred.  16.44 mmol potassium carbonate was dissolved in 10.75 g of H2O and added dropwise slowly to the mixture as to not raise the temperature above 40 degC.  The temperature never rose above 35 deg C. 

A solid was seen being formed.  After an additional hour stirring at RT the ixture was stopped and a highly viscous material was formed.  Upon putting in freezer over the weekend in solidified, where as the starting material is also in the freezer and stays a liquid.  The procedure says white, filterable crystals will form.  This is not the case.  I am going to run TLC.  What about GC of an oxime?  Do you guys advise GC of an oxime?

[Archer]

In my experience oximes are stable to GC analysis.

[clarkstill]

Did you distil the benzaldehyde prior to the reaction? In my experience it tends to be full of benzoic acid, which might be ruining your recryst?

This prep:

http://pubs.acs.org/doi/suppl/10.1021/ol052540c/suppl_file/ol052540csi20051026_052514.pdf

says the product only crystallized on prolonged standing, so maybe you need to wait longer...

[AlphaScent]

Thank you for the paper.

I am trying to write a overall synthetic method for preparation of oximes in our lab.  I am going to try the method outlined there in and will get back and post results. 

'Cheers