Can hydrogen be abstracted from urea?

[Vickyl Simpl]

Homework Statement

Urea is known to react with an acid to form salt. The carbonyl oxygen of urea is protonated in the process to form uronium ion. But, I have not seen conclusive reaction of urea with an alkali. So, if urea is dissolved in NaOH, what are the possible reactions? Can hydrogen be abstracted from one or both NH₂ group? What reagent can afford this abstraction if any.

Homework Equations

(NH₂)₂CO + HCl --> (NH₂)₂COH⁺ Cl^-
(NH₂)₂CO + NaOH --> ?
(NH₂)₂CO + ? --> HNCONH₂ ]^-
(NH₂)₂CO + ? --> HNCONH ]^2-

The Attempt at a Solution

 

[DrDu]

The reverse reaction, namely the hydrolysis of cyanamide is used in the preparation of urea. To reverse it, you will need a rather strong base. E.g. heating urea with metallic sodium.

 

[Borek]

You need to find pKa for these protons and then find a base strong enough. Definitely won't happen in water, and I doubt it will be possible to isolate such cations as salts, but organic chemists routinely use bases that should do the trick.

Edit: DrDu beat me.

 

[TeethWhitener]

http://evans.rc.fas.harvard.edu/pdf/evans_pKa_table.pdf
Evans gives the Bordwell pKa of urea at 26.9 in DMSO. So standard non-nucleophilic lithium bases like LDA or LHMDS should do the trick. (As should potassium dimsyl, the conjugate base of DMSO.)