Croconate blue
Encyclopedia
Croconate blue or 1,2,3-tris(dicyanomethylene)croconate is a divalent
anion with chemical formula
or ((N≡C-)2C=)3(C5O2)2−. It is one of the pseudo-oxocarbon anion
s, as it can be described as a derivative of the croconate
oxocarbon anion
through the replacement of three oxygen
atoms by dicyanomethylene group
s =C(-C≡N)2. The term Croconate Blue as a dye name specifically refers to the dipotassium
salt .
in 1978, together with croconate violet
. He obtained the corresponding acid, croconate acid blue by treating croconic acid
with malononitrile
in water solution at 80–90 °C.
The dipotassium salt is obtained from the acid by treatment with potassium methoxide from water as a green-blue trihydrate
, that slowly loses water converting to the dihydrate. The water solutions have an intense blue color. It quickly converts to croconate violet when treated with potassium hydroxide
. It is a weak semiconductor with conductivity 10−7 Ω−1 cm−1 at room temperature.
The bis(tetramethylammonium) salt ((CH3)4)2 is green-blue and crystallizes as the dihydrate.
Valence (chemistry)
In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...
anion with chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
or ((N≡C-)2C=)3(C5O2)2−. It is one of the pseudo-oxocarbon anion
Pseudo-oxocarbon anion
In chemistry, the term pseudo-oxocarbon anion is used to refer to a negative ion that is conceptually derived from an oxocarbon anion through replacement of one or more of the basic oxygen atoms by chemically similar elements or functional groups, such as sulfur , selenium , or dicyanomethylene...
s, as it can be described as a derivative of the croconate
Croconic acid
Croconic acid or 4,5-dihydroxycyclopentenetrione is a chemical compound with formula C5H2O5 or 32. It has a cyclopentene backbone with two hydroxyl groups adjacent to the double bond and three ketone groups on the remaining carbon atoms...
oxocarbon anion
Oxocarbon anion
In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula CxOyn− for some integers x, y, and n....
through the replacement of three oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atoms by dicyanomethylene group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
s =C(-C≡N)2. The term Croconate Blue as a dye name specifically refers to the dipotassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
salt .
History and synthesis
The anion was syntesized and characterized by A. FatiadiAlexander J. Fatiadi
Alexander J. Fatiadi is a chemist.He obtained his masters from the George Washington University, Washington DC . He has worked at the National Bureau of Standards.-Selected publications:...
in 1978, together with croconate violet
Croconate violet
Croconate violet or 1,3-biscroconate is a divalent anion with chemical formula or 22−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of two oxygen atoms by dicyanomethylene groups =C2...
. He obtained the corresponding acid, croconate acid blue by treating croconic acid
Croconic acid
Croconic acid or 4,5-dihydroxycyclopentenetrione is a chemical compound with formula C5H2O5 or 32. It has a cyclopentene backbone with two hydroxyl groups adjacent to the double bond and three ketone groups on the remaining carbon atoms...
with malononitrile
Malononitrile
Malononitrile, also propanedinitrile, is a nitrile, with formula CH22. Malononitrile is relatively acidic, with an pKa of 11 in water...
in water solution at 80–90 °C.
Croconate acid blue
Croconate acid blue is strongly acidic (pK1 ≈ 1). It crystallizes from water as a purple sesquihydrate ·1.5 and gives a red solution in acetone or ethanol, but deep blue in water. It hydrolizes slowly in water to give croconic acid violet. Extended heating in water produces deep green plates, apparently a polymer. Croconate acid blue retains the aromatic character and some other properties of the croconate anion.Croconate blue dianion
Unlike croconate violet, the croconate blue dianion is not planar; the three dicyanomethylene groups are twisted by about 30 degrees from the ring plane.The dipotassium salt is obtained from the acid by treatment with potassium methoxide from water as a green-blue trihydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
, that slowly loses water converting to the dihydrate. The water solutions have an intense blue color. It quickly converts to croconate violet when treated with potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
. It is a weak semiconductor with conductivity 10−7 Ω−1 cm−1 at room temperature.
The bis(tetramethylammonium) salt ((CH3)4)2 is green-blue and crystallizes as the dihydrate.
See also
- 2-(dicyanomethylene)croconate2-(Dicyanomethylene)croconate2-croconate is a divalent anion with chemical formula or 2−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of one oxygen atom by a dicyanomethylene group =C2.The anion was syntesized and...
- Croconate violetCroconate violetCroconate violet or 1,3-biscroconate is a divalent anion with chemical formula or 22−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of two oxygen atoms by dicyanomethylene groups =C2...
, 1,3-bis(dicyanomethylene)croconate - 1,2-bis(dicyanomethylene)squarate1,2-Bis(dicyanomethylene)squarate1,2-Bissquarate is a divalent anion with chemical formula or 22−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the squarate oxocarbon anion through the replacement of two adjacent oxygen atoms by dicyanomethylene groups =C2.The anion can be obtained...
- 1,3-bis(dicyanomethylene)squarate1,3-Bis(dicyanomethylene)squarate1,3-Bissquarate is a divalent anion with chemical formula or 22−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the squarate oxocarbon anion through the replacement of two opposite oxygen atoms by dicyanomethylene groups =C2.The anion can be obtained...