Melem (chemical compound)

Structural formula
General
Surname	Melem
other names	Triamino-tri- s -triazine 1,3,4,6,7,9,9b-heptaazaphenalen-2,5,8-triamine
Molecular formula	C 6 H 6 N 10
Brief description	white-beige powder
External identifiers / databases
CAS number 1502-47-2 EC number 216-122-4 ECHA InfoCard 100.014.657 PubChem 5462888 Wikidata Q1919260
properties
Molar mass	218.18 g mol −1
Physical state	firmly
density	1.717 g cm −3
Melting point	Decomposition from 560 ° C
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	2170 mg kg −1 ( LD 50 ,  rat ,  ip )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Melem is a polycyclic chemical compound from the group of the triazines and heptazines . It is one of the condensation products of melamine .

Extraction and presentation

The preparation is achieved by the condensation of cyanamide , Ammoniumdicyanamid , dicyandiamide or melamine in glass ampules for five hours at 450 ° C with a yield of about 60%. The synthesis takes place over several stages. First, dicyandiamide is formed from cyanamide or ammonium dicyanamide, which then cyclizes to form melamine. A condensation of melamine leads to the target compound with release of ammonia either directly or via the intermediate compound melam . In the large-scale production of melamine, the compound occurs in small quantities as a by-product.

properties

Melem is a white-beige, crystalline solid that shows no melting point . Above 560 ° C., only a decomposition is observed, which is based on further condensation reactions with elimination of ammonia and the formation of a graphite-like CN polymer . The compound crystallizes in a monoclinic crystal lattice with the space group P 2 ₁ / c (space group no. 14) . The molecule is almost planar with amino groups slightly twisted with respect to the molecular plane. The ¹³ C- NMR spectrum shows the signals at 164.3 / 166.4 ppm and 155.1 / 156.0 ppm for the two different carbon structures in the molecule  . Theoretically, four tautomeric structures can be drawn for the connection . However, it follows from the experimental database that only the structure with three NH ₂ groups is relevant. The molar heat of formation is 15.6 kJ mol ⁻¹ , the heat of combustion −3234 kJ mol ⁻¹ .

use

Melem is used in flame retardant combinations, especially in thermoplastic polymers . It is seen as a potential intermediate product for the production of carbon nitrides (C ₃ N ₄ ) _x in the graphite structure .

Individual evidence

1. ↑ ^{a b c d e f g h i} B. Jürgens; E. Irran; J. Senker; P.Kroll; H. Müller; W. Schnick: 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 in J. Am. Chem. Soc. 125 (2003) 10288-10300, doi : 10.1021 / ja0357689 .
2. ↑ There is not yet a harmonized classification for this substance . A labeling of 1,3,4,6,7,9,9b-heptaazaphenalene-2,5,8-triamine in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on 29. July 2019.
3. ↑ Entry on Melem in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on July 31, 2018 or earlier.
4. ↑ Ullmann's Encyclopedia of Industrial Chemistry, online version 2010 John Wiley & Sons Inc., Article Melamin , 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim doi : 10.1002 / 14356007.a08_139.pub2
5. ↑ L. Costa; G. Camino: Thermal Behavior of Melamine in J. Therm. Anal. 34 (1988) 423-429.
6. ↑ Selivanov, VD; Karlik, VM; Zagranicnyi, VI: Standard enthalpies of formation ammeline, ammelide, melem, and melon in Russ. J. Phys. Chem. (Engl. Transl.) 47 (1973) 272.
7. ^ Flame protecting combination