chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with formula or , whose molecule would consist of a
heptazine
Heptazine, or tri-''s''-triazine or cyamelurine, is a chemical compound with formula , that consist of a planar triangular core group or three fused triazine rings, with three hydrogen atoms at the corners. It is a yellow, weakly fluorescent soli ...
molecule, with three cyanamido groups or substituted for the
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
atoms.
The compound had not been properly isolated as of 2010, due to its tendency to
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
ize. However, removal of three protons yields the melonate (formerly hydromelonate) anion , whose salts are stable and have been known since the 19th century. Removal of only two protons yields the divalent hydrogenmelonate anion .
History
In 1834
Justus von Liebig
Justus Freiherr von Liebig (12 May 1803 – 20 April 1873) was a German scientist who made major contributions to agricultural and biological chemistry, and is considered one of the principal founders of organic chemistry. As a professor at t ...
described the compounds that he named
melamine
Melamine is an organic compound with the formula C3H6N6. This white solid is a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 67% nitrogen by mass, and its derivatives have fire retardant properties due t ...
,
melam
Melam is a group of Maddalams and other similar percussion instruments' (Chenda) rhythmic performance. Those who play melam are called 'Melakaar'. In ancient Tamilakam (Tamil country) melam was used for all the occasions in temples (''Kovil Melam ...
, and
melon
A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". The ...
. In 1835
Leopold Gmelin
Leopold Gmelin (2 August 1788 – 13 April 1853) was a German chemist. Gmelin was a professor at the University of Heidelberg He worked on the red prussiate and created Gmelin's test, and wrote his ''Handbook of Chemistry'', which over successiv ...
potassium ferrocyanide
Potassium ferrocyanide is the inorganic compound with formula K4 e(CN)6·3H2O. It is the potassium salt of the coordination complex e(CN)6sup>4−. This salt forms lemon-yellow monoclinic crystals.
Synthesis
In 1752, the French chemist Pierr ...
with
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
); recognizing their connection to the compounds described by Liebig, he named the salt "hydromelonate" and the corresponding acid "hydromelonic". In the following years Liebig prepared the same salt by other methods, such as by fusing
potassium thiocyanate
Potassium thiocyanate is the chemical compound with the molecular formula KSCN. It is an important salt of the thiocyanate anion, one of the pseudohalides. The compound has a low melting point relative to most other inorganic salts.
Use in chem ...
with
antimony trichloride
Antimony trichloride is the chemical compound with the formula SbCl3. It is a soft colorless solid with a pungent odor and was known to alchemists as butter of antimony.
Preparation
Antimony trichloride is prepared by reaction of chlorine with an ...
, and eventually determined the formula for the acid.
The correct structure for the cation was published in 1937 by
Linus Pauling
Linus Carl Pauling (; February 28, 1901August 19, 1994) was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific top ...
and J. H. Sturdivant.
Starting in the 1970s, melonates have attracted new interest, motivated by research in
cubic
Cubic may refer to:
Science and mathematics
* Cube (algebra), "cubic" measurement
* Cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex
** Cubic crystal system, a crystal system w ...
carbon nitride
In organic chemistry, carbon nitrides are compounds consisting only of carbon and nitrogen atoms.
Covalent network compounds
* Beta carbon nitride - a solid with a formula β-, which is predicted to be harder than diamond.
* Graphitic carbon ...
c-. Salts of many cations have been synthesized and studied, including mixed-cation salts and calcium hydrogenmelonate . The structure of potassium melonate pentahydrate was elucidated only in 2005.
Preparation
Sodium and potassium melonates are still routinely prepared by variations of one of Liebig's methods, namely by reacting
melon
A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". The ...
with molten
potassium thiocyanate
Potassium thiocyanate is the chemical compound with the molecular formula KSCN. It is an important salt of the thiocyanate anion, one of the pseudohalides. The compound has a low melting point relative to most other inorganic salts.
Use in chem ...
,
potassium cyanate
Potassium cyanate is an inorganic compound with the formula KOCN (sometimes denoted KCNO). It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was ...
, or
sodium thiocyanate
Sodium thiocyanate (sometimes called sodium sulphocyanide) is the chemical compound with the formula NaSCN. This colorless deliquescent salt is one of the main sources of the thiocyanate anion. As such, it is used as a precursor for the synthes ...
. Other salts can be prepared by
double displacement reaction
A salt metathesis reaction, sometimes called a double displacement reaction, is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding a ...
s.
Melonates
Alkali melonates are soluble in water without decomposition. Treatment of melonates with alkali gives salts of cyameluric acid.
Potassium melonate pentahydrate has planar sheets of melonate anions with potassium cations between the layers. The same generals structure is seen in the anhydrous salt (except that the melonate ions are asymmetric due to an group being turned by 180°) and in the salts and .
Melonate salts decompose when melted with
cyanate
Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate.
It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Small ...
s to form tricyanomelaminates, the first selective decomposition reaction leading from heptazines to
triazine
Triazines are a class of nitrogen-containing heterocycles. The parent molecules' molecular formula is . They exist in three isomeric forms, 1,3,5-triazines being common.
Structure
The triazines have planar six-membered benzene-like ring but ...
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
in the form of
nanotubes
file:Chiraltube.png, A scanning tunneling microscopy image of a single-walled carbon nanotube
file:Kohlenstoffnanoroehre Animation.gif, Rotating single-walled zigzag carbon nanotube
A carbon nanotube (CNT) is a tube made of carbon with diameters ...
.
See also
*
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 whit ...
J. Liebig, Ibid., 10, 1 (1834).L. Gmelin, Ann. Pharmacie, 15, 252 (1835).J. Liebig, Ann. Chem. Pharm., 50, 337 (1844).W. Henneberg, Ibid., 73, 228 (1850).J. Liebig, Ibid., 95, 257 (1855).Linus Pauling and J. H. Sturdivant (1937): "The Structure of Cyameluric Acid, Hydromelonic Acid and Related Substances". ''Proceedings of the National Academy of Sciences'', volume 23, issue 12, page 615–620. 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
The Ludwig Maximilian University of Munich (simply University of Munich or LMU; german: Ludwig-Maximilians-Universität München) is a public research university in Munich, Germany. It is Germany's sixth-oldest university in continuous operatio ...
Sophia J. Makowski, Daniel Gunzelmann, Jürgen Senker, Wolfgang Schnick (2009): "Protonated Melonate Ca C6N7(NCN)3·7H2O – Synthesis, Crystal Structure, and Thermal Properties". ''Zeitschrift für anorganische und allgemeine Chemie'' (''ZAAC''), volume 635, issue 15, pages 2434-2439. Andreas Sattler and Wolfgang Schnick (2009): "On the Formation and Decomposition of the Melonate Ion in Cyanate and Thiocyanate Melts and the Crystal Structure of Potassium Melonate,". ''European Journal of Inorganic Chemistry'', volume 2009, issue 33, pages 4972-4981. Corinna Clauss, Jörg Wagler, Marcus Schwarz, Anke Schwarzer, and Edwin Kroke (2010): "Lithium Melonate, – Synthesis, Crystal Structure and Thermal Properties of a Novel Precursor for Graphitic Carbon Nitrides". 'Zeitschrift für anorganische und allgemeine Chemie'' (''ZAAC''), vlume 636, issue 1, pages 196-200. Corinna Clauss, Marcus Schwarz, and Edwin Kroke (2010): "Microwave-induced decomposition of nitrogen-rich iron salts and CNT formation from iron(III)–melonate ". ''Carbon'', volume 48, issue 4,pages 1137-1145. Wolfgang Schnick and Sophia Makowski (2010): and – Synthesis, Crystal Structure and Thermal Behavior of two Novel Alkali Melonates . ''CSSD HAL'', article hal-00511998 version 1 {{doi, 10.1002/zaac.200900232Nitrogen heterocyclesHeterocyclic compounds with 3 ringsNitriles