Melem
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| Template:Longitem | 27284 |
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| Template:Longitem | 241276 |
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| Template:Longitem | C6H6N10 |
| Molar mass | 218.18 g/mol |
| Appearance | white solid |
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In chemistry, melem is a compound with formula Template:Chem/link; 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.[1]
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[N(CN)2], cyanamide H2CN2, at 400 to 450 °C.[1][2]
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.[1]
Thermal decomposition
When heated above 560°, melem transforms into a graphite-like C−N material.[1]
Melemium cations
Melem accepts up to three protons yielding cations called melemium Template:Chem2. Some salts described in the literature are melemium sulfate, Template:Chem/link • 2Template:Chem/link, melemium perchlorate, Template:Chem/link • Template:Chem/link, melemium hydrogensulfate Template:Chem/link and two melemium methylsulfonates Template:Chem/link • Template:Chem/link and Template:Chem/linkTemplate:Chem/linkTemplate:Chem/link • Template:Chem/link. The protons can be inserted in any of the six outer nitrogen atoms of the heptazine core, yielding many tautomers of apparently similar energies.[3]
See also
- Triazine Template:Chem/link, with a single C-N ring
- Melamine Template:Chem/link, triamino triazine
- Melaminium Template:Chem/link, a cation derived from melamine
- Melam Template:Chem/link, a condensation dimer of melamine
- Melamium Template:Chem/link, a cation derived from melam
- Melon Template:Chem/link, a condensation oligomer of melem
References
- ↑ a b c d Script error: No such module "Citation/CS1".
- ↑ Tamikuni Komatsu (2001)> Script error: No such module "Citation/CS1".
- ↑ 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