Selenourea

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Selenourea
Structural formula
Space-filling model
  Carbon, C
  Hydrogen, H
  Nitrogen, N
  Selenium
Identifiers
3D model (
JSmol
)
1734744
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.010.119 Edit this at Wikidata
EC Number
  • 211-129-9
239756
MeSH C081959
RTECS number
  • YU1820000
UNII
UN number 3283 3077
  • InChI=1S/CH4N2Se/c2-1(3)4/h(H4,2,3,4) ☒N
    Key: IYKVLICPFCEZOF-UHFFFAOYSA-N ☒N
  • InChI=1/CH4N2Se/c2-1(3)4/h(H4,2,3,4)
    Key: IYKVLICPFCEZOF-UHFFFAOYAJ
  • NC(N)=[Se]
Properties
SeC(NH2)2
Molar mass 123.028 g·mol−1
Appearance White solid; pink/grey solid when impure
Melting point 200 °C (392 °F; 473 K)
Boiling point 214 °C (417 °F; 487 K)
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H301, H331, H373, H410
P260, P261, P264, P270, P271, P273, P301+P310, P304+P340, P311, P314, P321, P330, P391, P403+P233, P405, P501
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Selenourea is the

heterocycles. Selenourea is a selenium analog of urea O=C(NH2)2. Few studies have been done on the compound due to the instability and toxicity of selenium compounds.[1]
Selenourea is toxic if inhaled or consumed.

Synthesis

The compound was first synthesized in 1884 by

Auguste Verneuil by the reaction of hydrogen selenide and cyanamide:[2]

H2Se + N≡C−NH2 → Se=C(NH2)2

While this reaction has even found use in industrial synthesis of selenourea,[3] more modern methods concern themselves with synthesis of substituted selenoureas. These can be synthesized using organic isoselenocyanates and secondary amines:

R−N=C=Se + NHR′R″ → Se=C(−NHR)(−NR′R″)

Alternatively, a substituted carbodiimide could be used as follows:[1]

R−N=C=N−R′ 1. HCl⟶2. LiAlHSeH Se=C(−NHR)(−NHR′)[clarification needed]

Properties

crystal lattice—suggested from the O−H and S−H hydrogen bonding found in crystals of urea and thiourea—was confirmed.[4]

Both the shortened length of the N−C bond and the longer Se=C bond suggest a delocalization of the

resonance structures, the selenol form (structures II, III) is more prevalent compared to urea and thiourea analogs; however, the lone pair the nitrogen of selenourea delocalizes only slightly more than the lone pair on thiourea (in contrast to a much greater delocalization in going from urea to thiourea).[5]
These minor differences suggest that the properties emergent from the delocalized nitrogen lone pair and destabilization of the C=S and C=Se π bond in thiourea and selenourea will also be similar.

Unlike urea and thiourea, which have both been researched extensively,

tautomerization
is available.

In comparable manner to ketones, selones also tautomerize:

Since the greater delocalization of the lone pair electrons correlates with the selone product, the equilibrium position of selenourea likely has an equilibrium position comparable to thiourea's (which is lies more to the right that than urea's). Thiourea has been shown to exist predominantly in its thione form at 42 °C in dilute methanol, with the thionol tautomer almost nonexistent at neutral pH.[7]

Reactivity

An important class of reactions of selenourea is the formation of

antitumor activity, among other medicinal uses. Using selenourea as a precursor is considered to be the most efficient means of selenium-containing heterocyclic synthesis.[8]

Another class of reactions is the complexation of selenourea with transition metals and metalloids. Its ability to act as an effective ligand is attributed to the electron-donating effect of the amino groups and consequent stabilization of the selenium–metal π bond. In selenourea complexes only selenium–metal bonding has been observed, unlike in the urea and thiourea counterparts, which also bond through the nitrogen atom.[9]

References

  1. ^
    doi:10.2174/157017906778699521
    .
  2. doi:10.3891/acta.chem.scand.18-1800
    .
  3. ^ Suvorov, V.; et al. (1996). "Production of selenourea of high purity". Vysokochistye Veshchestva. 3: 17–23.
  4. S2CID 98443594
    .
  5. doi:10.1039/J29680000673
    ..
  6. doi:10.1016/j.chemphys.2003.11.024
    .
  7. doi:10.1016/0014-3057(80)90122-6
    .
  8. doi:10.3987/REV-10-677 (inactive 2024-02-14).{{cite journal}}: CS1 maint: DOI inactive as of February 2024 (link
    )
  9. doi:10.1002/cber.19911241213
    .
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