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Vacuum Ultraviolet (VUV) Photodecomposition of Urea Isolated in Cryogenic Matrix: First Detection of Isourea

Vacuum Ultraviolet (VUV) Photodecomposition of Urea Isolated in Cryogenic Matrix: First Detection of Isourea

Fabrice Duvernay, Thierry Chiavassa, Fabien Borget, Jean-Pierre Aycard

J Phys Chem A. 2005 Jul 14;109(27):6008-18.

PMID: 16833937

Abstract:

Vacuum ultraviolet (VUV) irradiation at wavelengths of lambda > 160 nm of urea-h4 (NH2CONH2) and urea-d4 (ND2COND2) has been monitored by Fourier transform infrared spectroscopy in argon and xenon matrixes. Several primary photoproducts, such as HNCO:NH3 (isocyanic acid:ammonia), CO:N2H4 (carbon monoxide:hydrazine) molecular complexes, and isourea (H2N(OH)C=NH), which is reported for the first time, were characterized. The assignment of complexes was achieved by co-depositing the pairs of respective species, whereas the isourea identification was based on the comparison between the experimental and theoretical (B3LYP) infrared spectra. Isourea is found in the argon matrix in its most stable (s-Z)-(E) configuration. It is an intermediate in the VUV decomposition process; its dehydration leads to the NH2CN:H2O complex. In the xenon matrix, the photochemistry of urea yields the HNCO:NH3 complex as a major product, whereas the CO:N2H4 complex is observed in trace amounts. The observed differences between the argon and xenon matrixes suggest the crossing between S1 and T1 potential surfaces of urea to be responsible for the formation of the HNCO:NH3 complex. A comparison is also performed with other carboxamides, such as formamide (HCONH2) or acetamide (CH3CONH2).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1433110	Urea-d4		1433-11-0	Price

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