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Those are the reactions:

$$\ce{(H2N)2CO + 3 H2O -> CO2 + 2 NH4+ + 2OH-}$$ $$\ce{CH3COCH2COCH3 + OH- -> acac- + H2O}$$ $$\ce{CrCl3.6H2O -> Cr3+ + 3Cl- + 6H2O}$$ $$\ce{Cr3+ + 3acac- -> Cr(acac)}3$$

I don't get from where comes the $\ce{C5H8O2}$ in reaction #2!

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$\ce{CH3COCH2COCH3}$ is the condensed formula of pentane-2,4-dione, commonly known as acetylacetone. The $\ce{acac^-}$ is just a shorthand for the acetylacetonate ligand, i.e., $\ce{C5H7O2^-}$, which is just the deprotonated form of the acetylacetone used in reaction two.

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  • $\begingroup$ The first reaction has no specific purpose in the synthesis of $\ce{Cr(acac)_3}$, right? $\endgroup$ – Jerry May 22 '13 at 7:06
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    $\begingroup$ @Jerry, actually, the whole sequence of rxns. is bizarre. If the desired end product is $\ce{Cr(acac)3}$, there are infinitely more effective routes. I can only assume the first rxn. is the intended source of $\ce{OH^-}$. The problem is I'm fairly sure it doesn't work. One obvious reason is that the acid-base equilibrium between ammonium and hydroxide should favor the neutral species (water and ammonia) by 5-6 orders of magnitude. AFAIK, the hydrolysis of urea ultimately yields ammonia and carbon dioxide through an unstable carbamic acid intermediate, and, IIRC, enzyme catalysis is required. $\endgroup$ – Greg E. May 22 '13 at 8:07
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    $\begingroup$ Thank you, and yes, those reactions are really weird. $\endgroup$ – Jerry May 22 '13 at 8:11
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    $\begingroup$ Look like a co-reaction- (1) and (2) happen at the same time- just not in a simple combination so its represented as one reaction. (2) drives (1) towards hydroxyl formation. $\endgroup$ – user2617804 Dec 6 '13 at 13:28

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