In
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, 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 C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH4 (CN)2 cyanamide H2CN2, 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
[Barbara Jürgens, Elisabeth Irran, Jürgen Senker, Peter Kroll, Helen Müller, Wolfgang Schnick (2003): "Melem (2,5,8-Triamino-tri-s-triazine), an Important Intermediate during Condensation of Melamine Rings to Graphitic Carbon Nitride: Synthesis, Structure Determination by X-ray Powder Diffractometry, Solid-State NMR, and Theoretical Studies". ''Journal of the American Chemical Society'', volume 125, issue 34, pages 10288-10300. ]
[Tamikuni Komatsu (2001)> "The First Synthesis and Characterization of Cyameluric High Polymers". ''Macromolecular Chemistry and Physics'', volume 202, issue 1, pages 19-25. ]
[Fabian Karl Keßler (2019), ]
Structure and Reactivity of s-Triazine-Based Compounds in C/N/H Chemistry
'. Doctoral thesis, Fakultät für Chemie und Pharmazie, Ludwig-Maximilians-Universität München
Heterocyclic compounds with 3 rings
Nitrogen heterocycles
Tricyclic compounds
Amines
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