- Characteristics of quaternary compounds
- Chemical
- Physical
- Nomenclature
- Acid oxisales
- Basic oxisales
- Double salts
- Hydrated salts
- Training
- Examples
- References
The quaternaries are those having four different atoms or ions. Therefore, they can be molecular or ionic species. Its diversities include both organic and inorganic chemistry, being a very voluminous group; although perhaps not so much in comparison with binary or ternary compounds.
The reason that their number is smaller is because the four atoms or ions must be held together by their chemical affinities. Not all the elements are compatible with each other, and even less when it is considered a quartet; suddenly a pair of them are more akin to each other than to the other pair.
General and random formula for a quaternary compound. Source: Gabriel Bolívar.
Consider a quaternary compound of the random formula ABCD. The subscripts n, m, pey, are the stoichiometric coefficients, which in turn indicate what proportion of each atom there is in relation to the others.
Thus, the formula A n B m C p D y will be valid if it complies with electroneutrality. Furthermore, such a compound will be possible if its four atoms are sufficiently related to each other. It will be seen that this formula does not apply to many compounds, but mostly to alloys or minerals.
Characteristics of quaternary compounds
Chemical
A quaternary compound can be ionic or covalent, exhibiting the characteristics expected for its nature. Ionic ABCD compounds are expected to be soluble in water, alcohols, or other polar solvents; they should have high boiling and melting points, and be good conductors of electricity when melted.
Regarding the covalent ABCD compounds, most consist of nitrogenous, oxygenated or halogenated organic compounds; that is, its formula would become C n H m O p N and or C n H m O p X y, X being a halogen atom. Of these molecules it would be logical to think that they were polar, given the high electronegativities of O, N and X.
A purely covalent compound ABCD can have many bonding possibilities: AB, BC, DA, etc., obviously depending on the affinities and electronic capacities of the atoms. Whereas in a purely ionic ABCD compound, its interactions are electrostatic: A + B - C + D -, for example.
In the case of an alloy, considered more of a solid mixture than a proper compound, ABCD consists of neutral atoms in ground states (in theory).
Of the rest, an ABCD compound can be neutral, acidic or basic, depending on the identity of its atoms.
Physical
Physically speaking, it is likely that ABCD will not become a gas, since four different atoms always imply a higher molecular mass or formula. If it is not a high-boiling liquid, it is to be expected that it is a solid, the decomposition of which must generate many products.
Again, their colors, smell, texture, crystals, etc., will be subject to how A, B, C and D coexist in the compound, and will depend on their synergy and structures.
Nomenclature
So far the issue of quaternary compounds has been approached in a global and imprecise way. Organic chemistry aside (amides, benzyl chlorides, quaternary ammonium salts, etc.), in inorganic chemistry there are well-defined examples called acidic and basic oxysalts.
Acid oxisales
Acid oxysalts are those that derive from the partial neutralization of a polyprotic oxo acid. Thus, one or more of its hydrogens are replaced by metal cations, and the fewer remaining hydrogens it has, the less acidic it will be.
For example, from phosphoric acid, H 3 PO 4, up to two acid salts of, say, sodium can be obtained. These are: NaH 2 PO 4 (Na + replaces a hydrogen equivalent to H +) and Na 2 HPO 4.
According to traditional nomenclature, these salts are named like oxysalts (totally deprotonated), but with the word 'acid' preceding the name of the metal. Thus, NaH 2 PO 4 would be sodium diacid phosphate, and Na 2 HPO 4 sodium acid phosphate (because it has one H left).
On the other hand, the stock nomenclature prefers to use the word 'hydrogen' than 'acid'. The NaH 2 PO 4 would then become sodium dihydrogen phosphate, and the Na 2 HPO 4 sodium hydrogen phosphate. Note that these salts have four atoms: Na, H, P, and O.
Basic oxisales
Basic oxysalts are those that contain the OH - anion in their composition. For example, consider the salt CaNO 3 OH (Ca 2+ NO 3 - OH -). To name it, it would be enough to precede the word 'basic' to the name of the metal. Thus, its name would be: basic calcium nitrate. And how about CuIO 3 OH? Its name would be: cupric basic iodate (Cu 2+ IO 3 - OH -).
According to the stock nomenclature, the word 'basic' is replaced by hydroxide, followed by the use of a hyphen before the name of the oxoanion.
Repeating the previous examples, their names would be for each one: Calcium hydroxide-nitrate, and copper (II) hydroxide-iodate; remembering that the valence of the metal must be indicated in parentheses and with Roman numerals.
Double salts
In double salts there are two different cations interacting with the same type of anion. Suppose the double salt: Cu 3 Fe (PO 4) 3 (Cu 2+ Fe 3+ PO 4 3-). It is a phosphate of iron and copper, but the most appropriate name to refer to this is: triple phosphate of copper (II) and iron (III).
Hydrated salts
These are hydrates, and the only difference is that the number of water to formulate is specified at the end of their names. For example, MnCl 2 is manganese (II) chloride.
Its hydrate, MnCl 2 · 4H 2 O, is called manganese (II) chloride tetrahydrate. Note that there are four different atoms: Mn, Cl, H, and O.
A famous double and hydrated salt is that of Mohr, Fe (NH 4) 2 (SO 4) 2 · 6H 2 O. Its name is: double iron (II) sulfate and ammonium hexahydrate.
Training
Again, focusing on inorganic quaternary compounds, most of them are the product of partial neutralizations. If these occur in the presence of several metal oxides, it is likely that double salts will arise; and if the medium is very basic, the basic oxysalts will precipitate.
And if in addition, on the other hand, the water molecules have an affinity for the metal, they will coordinate directly with it or with the ions that surround it, forming the hydrates.
On the alloy side, four different metals or metalloids must be welded to make capacitors, semiconductors, or transistors.
Examples
Finally, a list with different examples of quaternary compounds is shown below. The reader can use it to test their knowledge of nomenclature:
- PbCO 3 (OH) 2
- Cr (HSO 4) 3
- NaHCO 3
- ZnIOH
- Cu 2 (OH) 2 SO 3
- Li 2 KAsO 4
- CuSO 4 · 5H 2 O
- AgAu (SO 4) 2
- CaSO 4 2H 2 O
- FeCl 3 · 6H 2 O
References
- Shiver & Atkins. (2008). Inorganic chemistry. (Fourth edition). Mc Graw Hill.
- Whitten, Davis, Peck & Stanley. (2008). Chemistry. (8th ed.). CENGAGE Learning.
- Nomenclature and inorganic formulation.. Recovered from: recursostic.educacion.es
- Erika Thalîa Good. (2019). Double salts. Academy. Recovered from: academia.edu
- Wikipedia. (2019). Quaternary ammonium cation. Recovered from: en.wikipedia.org