melem

In chemistry, melem is a compound with formula ; specifically, 2,5,8-triamino-heptazine or 2,5,8-triamino-tri-s-triazine, whose molecule can be described as that of heptazine with the three hydrogen atoms replaced by amino groups. It is a white crystalline solid.

In chemistry, melem is a compound with formula ; specifically, 2,5,8-triamino-heptazine or 2,5,8-triamino-tri-s-triazine, whose molecule can be described as that of heptazine with the three hydrogen atoms replaced by amino groups. It is a white crystalline solid.

Preparation

Melem can be prepared by thermal decomposition of various C−N−H compounds, such as melamine C 3 N 3 (NH 2 ) 3 , dicyandiamide H 4 C 2 N 4 , ammonium dicyanamide NH 4 [N(CN) 2 ], cyanamide H 2 CN 2 , at 400 to 450 °C.

Structure and properties

Crystal structure

Melem crystallizes in the group P21/c (No. 14), with parameters a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, β = 99.912(2)°, and Z = 4. The almost-planar molecules are arranged in parallel layers spaced 327 pm apart. The molecule is in the triamino form, rather than one of the possible tautomers.

Thermal decomposition

When heated above 560°, melem transforms into a graphite-like C−N material.

Melemium cations

Melem accepts up to three protons yielding cations called melemium . Some salts described in the literature are melemium sulfate, • 2 , melemium perchlorate, • , melemium hydrogensulfate and two melemium methylsulfonates • and • . The protons can be inserted in any of the six outer nitrogen atoms of the heptazine core, yielding many tautomers of apparently similar energies.

See also

Triazine , with a single C-N ring Melamine , triamino triazine Melaminium , a cation derived from melamine Melam , a condensation dimer of melamine Melamium , a cation derived from melam Melon , a condensation oligomer of melem

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=1291624789 under CC BY-SA 4.0; modifications have been made.