What is the chemical nomenclature?

We explain what is the chemical nomenclature, the nomenclatures in organic and inorganic chemistry and the traditional nomenclature.

1. What is the chemical nomenclature?

In chemistry , it is known as a nomenclature (or chemical nomenclature) to the set of rules that determine the way to name or call the various chemical materials known to human beings , depending on the elements that compose them and their proportion. As in biological sciences, there is an authority in the world of chemistry to regulate and order a nomenclature to make it universal.

The importance of chemical nomenclature lies in the possibility of naming, organizing and classifying the various types of chemical compounds, so that only with their identifying term can you have an idea of ​​what type of elements make it up and, therefore, what kind of reactions can be expected from the compound .

There are three chemical nomenclature systems:

• Stoichiometric or systematic system (IUPAC). Which names the compounds based on the number of atoms of each element that make up its basic molecule . For example: the compound Ni2O3 is called Dinyl Trioxide.
• Functional, classic or traditional system. It uses various suffixes and prefixes (such as “-oso” or “-ito”) depending on the valence of the elements of the compound. For example: the Ni2O3 compound is called nickel oxide.
• STOCK system In which the name of the compound includes in Roman numerals (and sometimes as a subscript) the valence of the atoms present in the basic molecule of the compound. For example: the Ni2O3 compound is called Nickel Oxide (III).

On the other hand, the chemical nomenclature varies depending on whether it is organic or inorganic compounds.

2. Nomenclature in organic chemistry

• Hydrocarbons Composed mostly of carbon and hydrogen atoms, with additives of various kinds, they can be classified into two types of functional groups: aliphatic, among which are alkanes, alkenes, alkynes and cycloalkanes; and aromatic, among which are monocyclic or mononuclear, and polycyclic or polynuclear (depending on the amount of benzene rings they present).
  • Alkanes Acyclic and saturated in nature, they respond to the general formula CnH2n + 2, the suffix -ano is used to name them, as follows:
    • In the case that they are linear, this prefix will be combined with the prefix that denotes the number of carbon atoms present: hexane, for example, has 6 carbon atoms (hex-).
    • If they are not linear but branched, the longest and most branched polycarbonated chain should be sought (the main chain), their carbon atoms are counted from the end closest to the branching and the branches are indicated indicating their position in the chain main, replacing the suffix -ano with -il and adding the corresponding numerical prefixes if there are two or more equal strings. Finally the main chain is usually named. For example: 5-ethyl-2-methyl-heptane is a heptane chain (hept-, 7 carbon atoms) with a methyl redical (CH3) in the second atom and one ethyl (C2H6) in the fifth.
    • Finally, the alkane radicals (produced by losing a hydrogen atom attached to a carbon one) are named by substituting the -ano for -yl and indicating the open chemical bond with a hyphen : the methyl radical comes out of methane (CH4) ( CH3-).
  • Cycloalkanes They are alicyclic, respond to the general formula CnH2n. They are named as alkanes, but adding the prefix cyclo- to the name, for example: Cyclobutane, Cyclopropane, 3-isopropyl-1-methyl-cyclopentane.
  • Alkenes and alkynes. Unsaturated hydrocarbons, as they have a double (alkene) or triple (alkynes) carbon-carbon bond. They respond, respectively, to the general formulas CnH2n and CnH2n-2. They are named similarly to alkanes, but various rules are applied based on the location of their multiple links:
    • When there is a double carbon-carbon bond, the suffix -eno is used and the respective number prefixes are added if they are more than one, for example: -diene, -triene, -tetraeno.
    • When there is a carbon-carbon triple bond, the suffix -ino is used and the respective number prefixes are added if there are more than one, for example: -diino, -triino, -tetraino.
    • When there are double and triple carbon-carbon bonds, the suffix -enino is used and the respective number prefixes are added if they are more than one, for example: -dienino, -trienino, -tetraenino.
    • The location of the multiple link with the number of the first carbon of that link is indicated.

Thus, we have the cases of: ethene (ethylene), propene (propylene) and tip, but from the four carbons the location of the bond is indicated with a number: 1-butene, 2-butyne, etc.

• • Aromatic hydrocarbons. Known as sands, it is benzene (C6H6) and its derivatives, and they can be monocyclic (they have only one benzene nucleus) or polycyclic (they have several).
    • Monocyclic They are named from derivations of the name of benzene, listing their substituents with numbering prefixes. Although they generally retain their vulgar name. For example: Methylbenzene (Toluene), 1,3-dimethylbenzene (o-xylene), hydroxybenzene (Phenol), etc.
    • Polycyclic They are mostly named by their vulgar name, since they are very specific compounds. But the suffix -eno can also be used for them, when they have the largest possible number of non-accumulated double bonds. For example: Naphthalene, Anthracene.
• Alcohols The alcohols are defined by the general formula R-OH, similar in structure to water , but replacing a hydrogen atom with an alkyl group. Its functional group is hydroxyl (-OH) and they are named using the suffix -ol instead of the ending -o of the corresponding hydrocarbon. If there are several hydroxyl groups, they are named by number prefixes. For example: Ethanol, 2-propanol, 2-propen-1-ol, etc.
• Phenols Phenols are identical to alcohols but with an aromatic ring attached to the hydroxyl group, following the formula Ar-OH. The suffix -ol is also used therein, together with that of the aromatic hydrocarbon. For example: o-nitrophenol, p-bromophenol, etc.
• Ethers. The ethers are governed by the general formula RO-R ‘, where the radicals of the ends may be identical or different groups, of the alkyl or aryl group. The ethers are named with the term of each alkyl or aryl group in alphabetical order, followed by the word “ether.” For example: ethyl methyl ether, diethyl ether, etc.
• Amines Derived from ammonia by replacing some of its hydrogens with alkyl or aryl radical groups, obtaining aliphatic amines and aromatic amines respectively. In both cases they are named using the suffix -amine or the vulgar name is preserved. For example: methylamine, isopropylamine, etc.
• Carboxylic acids. Formed by hydrogen, carbon and oxygen atoms, they are named considering the main chain of the highest carbon atoms that the acid group contains, and enumerating from the carboxylic group (= C = O). Then the name of the hydrocarbon with the same number of carbons and the -ico or -oic termination is used as a prefix, for example: methanoic acid or formic acid, ethanoic acid or acetic acid .
• Aldehydes and ketones. Both are compounds that have a carbonyl functional group, consisting of a carbon and an oxygen linked by multiple bonds (= C = O). If the carbonyl is at one end of the chain, we will talk about an aldehyde, and it will be in turn linked to a hydrogen and an alkyl or aryl group. On the contrary, we will talk about ketones when the carbonyl is within the chain and attached by the carbon atom to alkyl or aryl groups on both sides.
  • To name the aldehydes the suffix -al is used or by modifying the vulgar name of the carboxylic acid from which they come and changing the suffix -ico to -aldehyde. For example: methanal or formaldehyde, propanal or propionaldehyde.
  • To name the ketones the suffix -ona is used, or naming the two radicals attached to the carboxyl followed by the word ketone. For example: propanone or acetone, butanone or ethyl methyl ketone.
• Esters. They should not be confused with ethers, as they are acids whose hydrogen is substituted by an aquyl or aryl radical. They are named by changing the -ico acid suffix to -ato, followed by the name of the radical that replaces hydrogen, without the word “acid.” For example: Methyl ethanoate or methyl acetate, ethyl benzoate.
• Amides They should not be confused with amines, because they are produced by replacing the -OH group with the -NH2 group. The primary amides are named by replacing the -ico termination of the acid with -amide, for example: methanamide or formamide, benzamide. Secondary or tertiary ones also need to be named as N- or N derivatives. For example: N-methylacetamide, N-phenyl-N-methyl propanamide.
• Acid halides. Derivatives of a carboxylic acid in which the -OH group is replaced by an atom of a halogen element. They are named by replacing the suffix -ico with -ilo and the word “acid” with the name of the halide. For example: acetyl chloride, benzoyl chloride.
• Acid anhydrides Other carboxylic acid derivatives, which may or may not be symmetrical. If they are, they are named by just replacing the word acid with “anhydride.” For example: acetic anhydride (from acetic acid). If they are not, both acids are combined and preceded by the word “anhydride.” For example: Acetic acid anhydride and 2-hydroxy propanoic acid.
• Nitriles They are formed by hydrogen, nitrogen and carbon, the latter two joining a triple bond. In this case the -ico termination is replaced by -nitrile of the corresponding acid. For example: methanonitrile, propanonitrile.

3. Nomenclature in inorganic chemistry

• Oxides. Binary compounds with oxygen and some other element, which are named using prefixes, according to the amount of atoms that each oxide molecule has. For example: digalium trioxide (Ga2O3), carbon monoxide (CO). When the oxidized element is metallic, they are called basic oxides; When it is non-metallic, they are called anhydrides or acid oxides.
• Peroxides They consist of the reaction of a monoatomic oxygen and a metal, being named the same as the oxides but with the word “peroxide”. For example: calcium peroxide (CaO2), dihydrogen peroxide (H2O2).
• Superoxides Also known as hyperoxides, they occur when oxygen reacts with valence -1/2. And they are regularly named as oxides, but using the word “hyperoxide” or “superoxide”. For example: potassium superoxide or hyperoxide (KO2).
• Hydrides Compounds formed by hydrogen and another element, which when metallic are called metal hydrides and when not, hydrazides. Its nomenclature depends on the metallic or nonmetallic nature of the other element, although in some cases common names are privileged, as in ammonia (or nitrogen trihydride).
  • Metal. The term “hydride” and numeric prefixes are used depending on the amount of hydrogen atoms and. For example: potassium monohydride (KH), lead tetrahydride (PbH4).
  • Not metallic The terminal -uro is added to the non-metallic element and then “hydrogen” is added. For example: hydrogen fluoride (HF), dihydrogen selenide (SeH2).
• Oxacids Also called oxoacids or oxyacids (and popularly “acids”), their nomenclature requires using the prefix corresponding to the number of oxygen atoms, followed by the particle “oxo” attached to the name of the nonmetal ending in “-ato”, and then ” of hydrogen ”. For example: hydrogen tetraoxosulfate (H2SO4), hydrogen dioxosulfate (H2SO2).
• Hydroxides or bases. Formed by the union of a basic oxide and water, they are recognized by their functional group -OH, and are generically named as hydroxide, together with the respective prefixes depending on the amount of hydroxyl groups present. For example: lead dihydroxide (Pb [OH] 2), lithium hydroxide (LiOH).
• You go out. The salts are the product of the union of acidic and basic substances, and are named according to their classification: neutral, acidic, basic and mixed.
  • Neutral salts. They are formed after the union of an acid and a hydroxyl, releasing water in the process, and will be binary and ternary, depending on whether the acid is a hydrazide or an oxacid, respectively.
    • In the first case, they will be called haloidal salts and their nomenclature requires the use of the suffix -uro in the non-metallic element, as well as the prefixes corresponding to the number. For example: sodium chloride (NaCl), iron trichloride (FeCl3).
    • In the second case, they will be called ternary neutral salts and their nomenclature requires the use of the numerical prefix, the particle “oxo” and the suffix -ato in the nonmetal, followed by the valence of the nonmetal in brackets. For example: calcium tetraoxosulfate (VI) (CaSO4), sodium tetraoxophosphate (V) (Na3PO4).
  • Acid salts. They result from the replacement of hydrogen in an acid by metal atoms. Its nomenclature is equal to that of ternary neutral salts, but adding the word “hydrogen.” For example: sodium hydrogen sulfate (VI) (NaHSO4), potassium hydrogen carbonate (KHCO3).
  • Basic salts Due to the replacement of the oxidrils of a base with the anions of an acid, its nomenclature depends on whether the acid was a hydro acid or an oxidic acid.
    • In the first case, the name of the non-metal is used with the suffix -uro and the numeral prefix of the number of groups -OH is preceded, followed by the term “hydroxy”, and at the end of the entire valence in brackets of the metal , if necessary. For example: FeCl (OH) 2 would be iron (III) dihydroxychloride.
    • In the second case, the term hydroxy is used with its corresponding numeral prefix and the suffix -ato, adding the oxidation state of the central element in parentheses, and also the valence of the metal after its name, at the end. For example: Ni2 (OH) 4SO3 would be nickel (III) tetrahydroxytrioxosulfate (IV).
  • Mixed salts. Produced by replacing the hydrogens of an acid with metal atoms of different hydroxides. Its nomenclature is identical to that of acid salts, but including both elements. For example: sodium and potassium tetraoxosulfate (NaKSO4).

4. Traditional nomenclature

Much of the traditional nomenclature is still accepted in the IUPAC Red Book, and is well known for distinguishing between compounds based on the valence of their bound atoms , thus using the additives -oso, -ico; as much as the prefixes when it comes to more than two possible valences. It is, however, a deprecated nomenclature, gradually replaced by IUPAC, and which survives only in certain branches of commerce and industries.

5. IUPAC Nomenclature

IUPAC (International Union acronym of Pure and Applied Chemistry, namely, International Union of Pure and Applied Chemistry ) is the organization internationally dedicated to establishing universal rules and wield the authority on chemical nomenclature.

Its system, proposed as a simple and unifying system , is known as the IUPAC nomenclature and differs from the traditional nomenclature in that it solves many of the problems inherited from the history of chemistry , product of the gradual discovery of humanity of the basic laws that govern the matter.