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Important with the nomenclature (Naming) for chemical substances is that a compound name clearly and only leads to a single structural formula. The term "ethanol" denotes for example just the connection CH3-CH2-OH and no other. Conversely, chemical compounds do not have a clear name, e.g. B. one can use the connection CH3-CH2Designate -OH according to various nomenclature systems both as "ethanol" and as "ethyl alcohol".

In order to standardize the designations for chemical compounds, the IUPAC (International Union of Pure and Applied Chemistry) guidelines, which have been agreed as internationally binding, are nevertheless partly translated into "official" national-language designations (e.g. in German Space by the chemists' associations of Germany, Switzerland and Austria). The IUPAC itself also uses many English names in its element lists instead of the element abbreviations on which the element abbreviations are based (e.g. Potassium, Sodium, Tungsten, Mercury).

Since the systematic designation of chemical compounds according to these rules is often very complicated, chemists continue to use a large number of trivial names in everyday use (e.g. carbon dioxide instead of carbonmaterialdioxide, citric acid instead of 2-hydroxypropane-1,2,3-tricarboxylic acid).

Furthermore, national customs prevail for the element names, and even the IUPAC element roots do not consistently correspond to the name used for the formula abbreviations (example Hg = hydrargyrum, de. Mercury, IUPAC root "mercur" such as en. Mercury and antik Mercurius).

Number prefixes in chemical names

If a type of atom or group of atoms occurs more than once in a molecule, the number is indicated by a corresponding numerical prefix (prefix), which is derived from the Greek numerals and is placed in front of the name of the corresponding atom or group of atoms.

number Prefix
1 mono- or h-
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
11 and approx
12 dodeca
number Prefix
20 eicosa
21 heneicosa
22 docosa
23 tricosa
30 triaconta
40 tetraconta
50 pentaconta
60 hexaconta
70 heptaconta
80 octaconta
90 nonaconta
number Prefix
100 hecta
101 henhecta
200 dicta
222 docosadicta
300 tricta
362 dohexacontatricta
400 tetracta
500 pentacta
600 hexacta
700 heptacta
800 octacta
900 nonacta

Examples:

  • P4S.7Tetraphosphorusheptasulfide
  • CrO3 chrometrioxide
  • CH2Cl2Tuesdaychloromethane

Omission of number prefixes

If the name of a connection remains unique as a result, the number prefixes can also be omitted. So there are z. B. only a single oxide of aluminum, namely Al2O3why one instead Tuesdayaluminumtrioxide can also simply write aluminum oxide.

Very often the prefix mono- omitted, e.g. B. PH3 = Phosphane (instead of Monophosphane), although there is also a Tuesdayphosphane P2H4 gives.

Alternative number prefixes

If several identical groups are present where the use of the above prefixes would be ambiguous, the following prefixes derived from the Greek are used:

number Prefix
2 to
3 tris
4 tetrakis
5 pentakis
6 hexakis
etc.

Examples:

  • Approx5F (PO4)3 Pentacalcium fluoridetrisphosphate - By using the prefix tris it is immediately clear that it is not the triphosphate group [P3O10]5- is, but three phosphate groups [PO4]3-.
  • 5,6-To(1,1-dimethylpropyl) undecane - the use of the prefix to immediately shows that these are two identical 1,1-dimethylpropyl substituents.

For the direct linking of identical units the following prefixes are used, which are derived from the Latin numerals:

number Prefix
2 bi
3 ter
4 quater
5 quinque
6 sexi
7 septi
etc.

Example:

  • C.6H5-C6H5 called Biphenyl (and not diphenyl or bisphenyl).

Inorganic chemistry

Element names and symbols

The Names of the chemical elements are determined by the discoverers and are listed here. For unknown or new elements that have not yet been given a name, there are systematic element names that are derived from the atomic number. The periodic table of the elements offers a systematic arrangement of the elements according to their electronic configuration.

There is an abbreviation of one to three letters for each element (Element symbol). These symbols are listed below for the main and subgroup elements. The element symbols are internationally valid, so they are also represented in Japanese using Latin letters, for example.

Do you want a certain one isotope denote an element, its mass number is put in superscript in front of the element symbol, for example 12C for the carbon-12 isotope, 235U for uranium 235, etc. The heavy isotopes of hydrogen are an exception, 2H (deuterium) and 3H (tritium), which with D. or. T have their own element symbol.

In order to name connections between different elements, the element names are partially modified and given suffixes. To do this, one uses the Element roots in the following table, which are derived from the Latin element names. For example, the oxygen in the compound becomes aluminumoxid (Al2O3) by its element root (ox) and the ending -id specified.

Main group elements

Transition elements

Formulas of inorganic compounds

When writing formulas of chemical compounds, one essentially follows the electronegativity scale of the chemical elements. You always start with the more electropositive connection partner, which is why you write AgCl, Al2O3, PCl5 and not the other way around.

Hydrogen compounds are an exception to this rule. Hydrogen atoms are written in the formulas last (NH3, SiH4, Etc.). However, if it is acidic hydrogen (i.e. the compound reacts acidic in aqueous solution), then one writes the hydrogen at the beginning of the formula (HF, HCl, HBr, HI, H2O, H2O2, H2S, H2Se, H2Te, H3N). In the case of inorganic oxo acids, the hydrogen is also written at the beginning of the formula, although it is actually bound to oxygen, i.e. for sulfuric acid, for example, H2SO4 instead of SO2(OH)2.

Cations (even only formal ones) always keep the element name. Anions get their name systematically after the acid from which they are derived, regardless of whether it is actually an ionic bond or a covalent bond. The nomenclature for coordinative compounds, i.e. complexes, works a little more complicated and is described there in more detail.

Hydrogen acid anions

Ending in -id

The simplest anions are those of the hydrogen acids. The element anion remains with them after the proton has been released.

These anions form their ending with id appended to the element name. The most important are:

7th main group (halides)

Fluoride (F-), chloride (Cl-), bromide (Br-), iodide (I.-)
Example:

6th main group

Oxide (O2-), sulfide (p2-), selenide (Se2-)
Example:

5th main group

Nitride (N3-), phosphide (P.3-)
Example:

4th main group

rarely occur
Example:

Oxygen or oxo acids and their anions

All endings except "id" are due to acids that contain oxygen in addition to the eponymous element. Since there are a large number of these compounds, the systematics are first explained and the individual acids are listed in a table at the end of the paragraph.

Element acids (-at)

here generally applies:
7. Main group:
Halogenic acid HXO3 z. B. Chloric acid HClO3 with the anion chlorate (ClO3-)
6. Main group:
Element acid H2XO4 z. B. Sulfuric Acid H2SO4 with the anion sulfate (SO42-)
5th main group:
Element acid H3XO4 z. B. Phosphoric Acid H3PO4 with the anion phosphate (PO43-); Exception: nitric acid
4th main group:
Element acid H2XO3 z. B. Carbon Acid (Carbonic Acid) H2CO3 with the anion carbonate (CO32-)
3rd main group:
Element acid H3XO3 z. B. Boric Acid H3BO3 with the anion borate (BO33-)

Per-acids (per ... -at)

These acids also have an oxygen atom. Not all oxo acids exist, but if they are formed, the oxidation state of the element increases by two compared to that of the oxo acid. Mainly these acids are formed by the halogens:

7. Main group:
Perhalic acid HXO4 z. B. Perchloric acid HClO4 with the anion perchlorate (ClO4-)

"Elemental" acids (-it)

These acids have one less oxygen atom than the element acids. z. B. Nitrous acid ENT2 with the anion NO2- Nitrite, chlorous acid HClO2 with the anion ClO2- chlorite, sulphurous acid H2SO3 with the anion HSO3- hydrogen sulfite

"Hypo-elemental" acids (hypo ... -it)

These acids have one oxygen atom less than the elemental acids. z. B. Hypochlorous acid HClO with the anion hypochlorite ClO-

Multiple oxidation states of the electropositive partner

Alloys

Hydrogen compounds

Complex anions

There are also guidelines for naming complexes.

radical

To name the radical, the ending -yl is added to the stem name. This applies to both organic and inorganic chemistry.

Examples: HO-: Hydroxyl (parent: hydroxy-) CH3-: Methyl (stem: meth-)

Some radicals have special names, especially when it comes to oxygen compounds.

Polybasic acids

Salt hydrates

Classification according to the oxidation state of the central atom

Classification according to the structure

List of oxo acids and anions

Organic chemistry

For the naming of organic compounds according to the IUPAC system, one usually starts from one Root system off, which may be further Substituents (Remnants) carries. A substituent is an atom or a combination of atoms that replaces (substitutes) a hydrogen atom in the parent system. The name of the parent system is used unchanged for naming the compound and the names of the substituting groups are added to the parent system in a modified form (substitutive nomenclature).

Trunk systems

Linear chains

The simplest parent systems are linear chains of carbon atoms in which all other bonds are saturated with hydrogen atoms. Such saturated hydrocarbons are called alkanes, they get the ending -at. For the four smallest alkanes, the names methane, ethane, propane and butane are retained; for the remaining alkanes, the exact name of the compound is derived from the following table Number of carbon atoms. Combine the numerical word for the first decade with the numerical word for the following decades. At the end there is an n, giving the alkane-typical ending -at receives.

1 Hen 10 Deca 100 Hecta 1000 Kilia
2 do 20 Cosa 200 Dicta 2000 Dilia
3 Tri 30 Triaconta 300 Tricta 3000 Trilia
4 Tetra 40 Tetraconta 400 Tetracta 4000 Tetralia
5 Penta 50 Pentaconta 500 Pentacta 5000 Pentalia
6 Hexa 60 Hexaconta 600 Hexacta 6000 Hexalia
7 Hepta 70 Heptaconta 700 Heptacta 7000 Heptalia
8 Octa 80 Octaconta 800 Octacta 8000 Octalia
9 Nona 90 Nonaconta 900 Nonacta 9000 Nonalia

Examples:

  • C.32H66 = Dotriacontan (Do + Triaconta + n)
  • C.99H200 = Nonanonacontan (Nona + Nonaconta + n)
  • C.403H808 = Tritetractan (Tri + Tetracta + n)
  • C.4728H9458 = Octacosaheptactatetralian (Octa + Cosa + Heptacta + Tetralia + n)
  • C.9999H20000 = Nonanonacontanonactanonalian (Nona + Nonaconta + Nonacta + nonalia + n) M = 139.988Kg / mol

There are exceptions to the naming according to the table above for:

Number of carbon atoms connection Surname
1 CH4methane
2 C.2H6Ethane
3 C.3H8propane
4 C.4H10butane
11 C.11H24Undecane
20 C.20H42Eicosan
21 C.21H44Heneicosan

If there is a double bond in the compound, the term alkenes is used and the ending is used instead -at the ending -en. The position of the double bond is indicated by a number see below at numbering), e.g. B.

  • CH2= CH-CH2-CH3 is called 1-buten (or but-1-en),
  • CH3-CH = CH-CH3 is called 2-buten.

For chains that contain a triple bond (= alkynes), the ending -in used e.g. B.

  • CH≡C-CH2-CH3 is called 1-butin (or but-1-in),
  • CH2= CH-CH2-C≡C-CH2-CH3 is called Hept-1-en-4-in.

If there are several double or triple bonds, the multiplying prefixes are used di, tri, tetra, penta, hexa, hepta, …

  • CH2= CH-CH = CH2 is called buta-1,3-diene,
  • CH≡C-C≡C-C≡C-CH3 is called hepta-1,3,5-triine.
Determination of the main chain in branched acyclic hydrocarbons

The main chain (stem system) is the chain which

  1. contains the largest number of multiple bonds
  2. if (1) is ambiguous: contains the larger number of carbon atoms
  3. if (2) is ambiguous: contains the larger number of double bonds
  4. if (3) is ambiguous: has the lowest locant set for the multiple bonds.
  5. if (4) is ambiguous: has the lowest locant set for the double bonds.
  6. if (5) is ambiguous: has the larger number of substituents.
  7. if (6) is ambiguous: has the lowest locant set for the substituents.
  8. if (7) is ambiguous: has the first substituent in alphabetical order.
  9. if (8) is ambiguous: has the lowest locant for the alphabetically first substituent.

Cyclic systems without heteroatoms

In cyclic systems, one cycle is generally the parent system.

Monocyclic systems

If it is a monocyclic compound, the naming is the same as for linear chains, with the addition of the prefix Cyclo- prefixed, e.g. B. Cyclohexane. The common name is retained for benzene.

Monocyclic compounds with more than six carbon atoms, which have the maximum number of non-cumulative double bonds, can be referred to as (n) -annulenes (n = number of carbon atoms).

Cyclic systems are preferably designated according to the Hantzsch-Widmann-Patterson nomenclature.

Condensed polycyclic systems

At condensed polycyclic hydrocarbons (i.e. the individual rings are each linked via exactly one common bond) that component is the basic system which

  • has most of the rings
  • has the largest ring

The following polycycles are regarded as separate systems (in increasing priority, the number of rings in brackets):

Pentalene (2), indene (2), naphthalene (2), azulene (2), heptalene (2), biphenylene (3), as-indacene (3), s-indacene (3), acenaphthylene (3), fluorene (3), phenals (3), phenanthrene (3), anthracene (3), fluoranthene (4), acephenanthrylene (4), aceanthrylene (4), triphenylene (4), pyrene (4), chrysene (4), naphthacene (4), Pleiaden (chemistry) (4), picen (5), perylene (5), pentaphene (5), pentacene (5), tetraphenylene (5), hexaphene (6), hexacene (6), rubicene (7 ), Corones (7), trinaphthylene (7), heptaphene (7), heptacene (7), pyranthrene (8), ovals (10).

All other rings are prefixed as prefixes, with the final syllable -en in -eno is converted (e.g. Benzocyclooctene). The type of link is indicated by numbers and letters, but this is not to be explained in more detail here.

To name saturated or partially saturated derivatives of the polycycles listed above, there is the option of adding the item numbers and the prefix to the two additional hydrogen atoms if a double bond is omitted dihydro to display. There is analogue tetrahydro, hexahydro etc. Fully saturated systems are given the prefix perhydro. Individual hydrogen atoms are produced by the so-called indexed H indicated, which is placed in front of it in italics (e.g. 4H-Pyrazole).

Cyclophanes can be named according to the same rules, although they also have their own nomenclature.

Bridged polycyclic systems

At bridged polycyclic hydrocarbons (i.e. the individual rings are each linked by more than one common bond) the von Baeyer system is used.

Spiro compounds

The nomenclature of spiro compounds is explained (in little detail) under the corresponding key word.

More complex systems

The decision of what is now to be regarded as the root system is no longer easy with more complex connections.

Heterocycles

If there are no trivial names, monocyclic heterocycles with up to 10 ring members are usually named according to the Hantzsch-Widmann-Patterson nomenclature.

In the case of condensed polycycles, heterocycles have priority over carbocycles (= rings that only consist of carbon atoms). There are also systems with trivial names for heterocycles, which are understood as separate stem systems (without ranking and incomplete):

Otherwise, the naming of heterocycles largely follows the rules given above for cyclic systems without heteroatoms. The type and position of the heteroatoms is then indicated using the exchange nomenclature or "a" nomenclature.

Substituents (residues)

A substituent can e.g. B. be a functional group, or in turn a (smaller) parent system, such as a side chain. The names for substituents are added to the name of the root system as prefixes or endings (suffixes). The exact position of the substituent is specified by numbers (see below at numbering).

If there are several prefixes, they are listed in alphabetical order.

Parent systems as substituents

If the remainder is a stem system, for example a side chain or a ring, the syllable is added to its name -yl appended and the result as a prefix. The naming of side chains follows the same rules as for the basic chain, with the following exceptions:

  • for alkanes the ending -at omitted
  • the numbering of the side chain always starts with the link with the main chain

Examples:

  • Methyl: -CH3
  • Ethyl: -CH2-CH3
  • Ethynyl: -C≡CH
  • Propenyl: -CH2-CH = CH2
  • Cyclohexyl: -C6H11

For example, if you think of the compound propane (CH3-CH2-CH3) a methane building block is attached in the middle, the resulting compound is called CH3-CH (CH3) -CH3) then 2-methylpropane. The connection CH3-CH2-CH (CH3) -CH2-CH (CH2CH3) -CH2-CH3 called 3-ethyl-5-methylheptane.

Functional groups

The highest-ranking functional group is added as an ending (suffix), other functional groups as prefixes:

  • CH3-CH (OH) -CH3 is called propane-2-oil
  • CH3-CH2-CH2-C (OOH) is called butaneacid
  • CH2-CH (OH) -CH2-CH (NH2) -CH2-CH3 has two functional groups. The alcohol has higher priority, that's why the connection is called 4-aminohexane2-ol.

For the names of individual functional groups and their order of precedence, see the keyword functional group.

Common names

For some substituents there are trivial names, which z. T. are also binding. E.g .:

  • Phenyl: -C6H5
  • Benzyl: -CH2-C6H5
  • Isopropyl: -CH- (CH3)2
  • Vinyl: -CH = CH2
  • and much more m.

numbering

The master system is numbered in such a way that the numbers received are as small as possible. CH3-CH2-CH (CH3) -CH3 is called 2-methylbutane and not 3-methylbutane.

A 1 can also be left out (e.g. propanol = propan-1-ol). If there is only one possible combination, the numbers can also be left out (e.g. methylpropane = 2-methylpropane, because anything other than butane would have to be named).

If side chains have to be numbered, the connection point to the main chain is always position 1.

In the case of condensed polycyclic systems, there are often binding methods of numbering that can be described as contradicting any logic and consequently have to be memorized.

The position numbers are called locants.

Repeatedly occurring substituents

For groups that occur more than once, the multiplying prefixesdi, tri, tetra, penta, hexa, hepta, ... (see above) used:

If the use of di, tri, tetra, etc. would be misleading, for example with identical further substituted side chains, the appropriate alternative prefixes bis, tris, tetrakis, etc. must be used as described above. The prefixes bi, ter, quater, etc. are used for directly linked identical units.

example

According to the IUPAC nomenclature, for example, the substance

NH2-CH2-CH2-OH

received the name 2-aminoethanol.

You can get this name in the following way:

  1. Since the carbon atoms only have single bonds, the root is given “an” as the first ending.
  2. The basic chain contains two carbon atoms; this results in the root "eth". (→ "ethane")
  3. The functional groups are an alcohol (OH) and an amino group (NH2). The alcohol group has the higher priority and takes precedence over the amino group. So append "ol" to the end. (→ "ethanol")
  4. The amino group is not on the same carbon atom as the alcohol group (atom no. 1), but on the one next to it (no. 2). That is why we indicate the location using “2-Amino”.
  5. The combination of prefix, root and endings results in the name "2-aminoethanol".

Stereochemistry

Chiral connections

The prefixes in italics are used to distinguish between chiral compounds (R.)- and (S.)-. Their use is determined by the Cahn-Ingold-Prelog rule (CIP rule) and its subsidiary rules.

For biochemical substances such as carbohydrates and amino acids, the Fischer nomenclature is often used, which includes the prefixes D.- and L.- used (where D. and L. written as small caps).

The prefixes are used to distinguish the sense of rotation in optically active compounds (+)- and (−)-, whereby there is no connection between the optical activity (sense of rotation) and the “direction” chirality.

It should be noted that the different ways of naming (R., S. or. D., L. and +, -) according to the different types of nomenclature Not can be derived from the other names. Only the CIP rules are suitable for the systematic designation of compounds with several centers of chirality, the Fischer nomenclature for sugar, for example, being much more compact.

cis-trans isomers

In cis-trans isomerism, a distinction is made in the nomenclature between compounds that have only two different substituents and compounds with more than two. The former are with the prefixes in italics cis- or trans-. cis- are according to IUPAC with a preceding, italic (Z) ("Together") and trans- with a (E) ("Opposite") marked.

In the first picture you can see trans-1,2-dibromoethene, on the second the cis-Version. You could also use the E / Z prefixes here, trans-1,2-dibromoethene could also (E)-1,2-dibromoethene are called.

Here on the ring, too, the two bromines are in the cis position (“together” on one side).

That is a (Z)-3-methyl-2-pentene, since the higher substituents (see stereochemistry) are on one side.

Anomers

In the case of carbohydrates, anomers are distinguished by the italic prefixes α- or. β-.

biochemistry

IUPAC and IUBMB (International Union of Biochemistry and Molecular Biology) have shared guidelines for the nomenclature of enzymes. After this nomenclature, enzyme names end with -ase and contain information about the function of the enzyme. Details under the keyword enzyme and on the IUBMB website.

In addition, a code system (please referEC numbers) in which the enzymes can be found under a four-digit code.

Chemical nomenclature outside of IUPAC regulations

  • There are abbreviations defined by a DIN standard for plastic names.
  • There is an E-number system for food additives.

literature

  • Karl-Heinz Hellwich: Chemical nomenclature. GOVI publishing house, ISBN 3-7741-0815-3.
  • D. Hellwinkel: The systematic nomenclature of organic chemistry. A manual. 4th edition. Springer, Berlin 1998, ISBN 3-540-63221-2.

English

  • IUPAC website
  • IUBMB website
  • IUPAC Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. (English)
  • IUPAC rules on nomenclature in organic chemistry
  • Online Naming Tool (English, requires Java)
  • IUPAC nomenclature in stereochemistry
  • Comparison of chemical names generated with nomenclature software and published by authors. Gernot A. Eller: Improving the Quality of Published Chemical Names with Nomenclature Software. In: Molecules. 2006, 11, 915-928 (online article in English)

Category: Chemistry