[BARAJAN]

hi guys
in the attached reaction
I have used NH₂OH (without using any base or acid) instead of NH₂OH.HCl for hydroxyurea synthesis but the product seems to be ethylcarbamate (starting material due to m.p).
what is my mistake?
the original procedure is addressed here:
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0645
do you think the nucleophilicity of NH2OH and NH2OH.HCl are different (like their polarity)!!!
thanks for your help

[orgopete]

I'm not sure what has been done. Was NH2OH prepared first and then added? If the question is whether there is a difference in reactivity, then yes. Hydroxylamine hydrochloride is tied up as the hydrochloride and so is less reactive. I'd follow the org syn prep if it were me.

[BARAJAN]

I'm not sure what has been done. Was NH2OH prepared first and then added?

no, it was purchased from Merck co. in 50% aques solution.
I have searched some older reports for hydroxyurea synthesis something is very strange to me that is why most of the reports has performed the reaction with hydrocholride salt. 
I think there most be something about these two compounds that I don't know

[orgopete]

Two things here. I would not expect any difference between hydroxylamine and in situ prepared hydroxylamine, but that may not be true, the hydrochloride may be more stable. That may explain why the hydrochloride was used in the org syn prep.

The second possibility may be related to Note 2 in that the product is unstable at low pHs.