Chemical nomenclature

Under nomenclature is understood in the chemistry, the possible systematic and internationally uniform as possible for naming chemical substances. It is now regarded as important that a connection name is unique and requires only a single structural formula. The term " ethanol " refers to, for example, only the compound CH 3 -CH 2- OH, and no other. Conversely, chemical compounds but not a unique name, for example, the compound CH3 -CH2- OH to different nomenclature systems refer to both as " ethanol " as well as " ethyl alcohol ".

• 4.1 element names and symbols 4.1.1 Main Group Elements
• 4.1.2 Transition Elements

• 4.2.1 anions of hydrogen acids
• 4.2.2 Oxygen or oxo acids and their anions 4.2.2.1 Element acids ( - at)
• 4.2.2.2 Per- acids ( per ... - at)
• 4.2.2.3 " Elementige " acids ( -it )
• 4.2.2.4 " Hypoelementige " acids ( hypo -it ... )

• 4.5.1 Classification by structure

• 5.1 root systems 5.1.1 Linear chains 5.1.1.1 Determination of the backbone in branched acyclic hydrocarbons

• 5.1.2.1 Monocyclic systems
• 5.1.2.2 Condensed polycyclic systems
• 5.1.2.3 Bridged polycyclic systems
• 5.1.2.4 spiro compounds
• 5.1.2.5 More complicated systems

• 5.2.1 root systems as substituents
• 5.2.2 Functional Groups
• 5.2.3 Trivial name

• 6.1 Chiral Compounds
• 6.2 cis -trans isomers
• 6.3 anomers

History

Until the 18th century the name of chemical substances was very uneven. An important step towards systematization presented in 1787 the book Méthode de nomenclature Chimique of Louis Bernard Guyton de Morveau, Antoine Laurent de Lavoisier, Claude Louis Berthollet and Antoine François de Fourcroy dar. Jöns Jakob Berzelius led to the 1825 chemical sign language with letters for chemical elements one. 1860 proposed a committee headed by Friedrich August Kekulé before an international designation system for organic compounds. The International Union of Pure and Applied Chemistry (IUPAC) was founded in 1919. Since then, she considers the establishment of international standards for chemical nomenclature as their main task.

The IUPAC nomenclature

To unify the notations for chemical compounds, there are agreed as binding international guidelines of the IUPAC ( International Union of Pure and Applied Chemistry ) and the IUBMB (International Union of Biochemistry and Molecular Biology ) and their joint used to compensate Commission Commission on Biochemical Nomenclature. These govern the English language. The names in other languages ​​will be transferred from the national associations according to chemists, for example, in German-speaking countries by the German Chemical Society ( German Chemical Society ), Switzerland and Austria. The IUPAC even used in their element lists many English names instead of the element shortcuts underlying (eg, Potassium, Sodium, Tungsten, Mercury ). The needs of different languages ​​and even the English themselves are explicitly recognized by the IUPAC. Particularly stringent nomenclature rules were necessary in particular for Index-Werke for chemical substances such as the Beilstein Handbook of Organic Chemistry and Chemical Abstracts, until recently, as their system for finding entries to the introduction of electronic research mainly took place afterwards.

Since the systematic name of chemical compounds according to these rules is often very complicated, a large number of traditional names and newly created, recognized nickname is used by chemists in everyday use to scientific publications continue. The IUPAC distinguishes between trivial names that have no relation to the systematic nomenclature have (eg water, urea, or Glauber's salt), semi- systematic names or Semi Trivial names that at least a part of a systematic name (for example, carbon dioxide instead of carbon dioxide, trityl for triphenylmethyl group or glycerol for propane -1 ,2,3 -triol ) and the aforementioned systematic name. Also for the invention of new trivial names, such as newly discovered natural products, there are IUPAC -compliant rules.

Furthermore, in the element name reign the national customs before, and even the IUPAC element roots do not correspond consistently the law applicable to the formula shortcut name (example Hg = Hydrargyrum, dt mercury, IUPAC root " mercure " as Engl. Mercury and Latin Mercurius ).

Zahlenpräfixe in chemical name

If one kind of atoms or groups of atoms in a molecule occurs more than once, the number is indicated by a corresponding Zahlenpräfix ( prefix ) that is derived from the Greek words and number is prepended to the name of the corresponding atom and the corresponding atomic group.

Examples:

• P4S7 Tetraphosphorheptasulfid
• SO3 sulfur trioxide
• Dichloromethane CH2Cl2

Omitting Zahlenpräfixen

With metal compounds is called only the valence or oxidation number, which has the metal in said compound ( ionic bonding ). eg CrO3 Chromium (VI ) oxide, chromium six read -oxide instead of chromium trioxide. The valence or oxidation number is thereby indicated with Roman numerals. If the name of a compound thus remains clear, you can also omit the value. There are, for example, only a single oxide of aluminum, namely Al2O3, which is why instead of aluminum (III ) oxide can also simply write alumina.

Very often, the prefix is mono omitted, such as phosphine PH3 = (instead monophosphane ), although there is a diphosphine P2H4.

Alternative Zahlenpräfixe

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

Examples:

• Ca5F (PO4) 3 Pentacalciumfluoridtrisphosphat - tris By using the prefix is immediately clear that this is not the triphosphate [ P3O10 ] 5 - is but about three phosphate groups [ PO4 ] 3 -.
• 5,6 -bis (1,1- dimethyl-propyl ) undecane - the use of the prefix to immediately shows that this is two identical 1,1- dimethyl propyl substituent.

For the direct linking of identical units using the following prefixes, which are derived from the Latin number words:

Example:

• C6H5 - C6H5 is called biphenyl ( diphenyl or not and biphenyl ).

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 items that have not yet received a name, there are systematic element name, derived from the nuclear charge. A systematic arrangement of elements according to their electron configuration provides the periodic table of elements.

For some elements exist old German names that have been adapted in several revisions of IUPAC to in English. This primarily element names in which the letters were k and z replaced by c. Examples are calcium - calcium, silicon - silicon or cobalt - cobalt. But some other notation such as iodine, the iodine was changed to bismuth or bismuth to have been changed. While in chemistry mainly the new names are used, the old names are used in other areas and in common area often still.

For each element, there is a shortcut from one to three letters ( element symbol ). These symbols are listed below for the main group and transition elements. The element symbols are valid internationally, they will say for example reproduced in Japanese by Latin letters.

If you want to designate a specific isotope of an element, we can see the mass number in superscript before the element symbol, for example, 12C for the carbon-12 isotope, 235U, uranium 235, etc. An exception is the heavy isotopes of hydrogen, 2H (deuterium ) and 3H ( tritium), which have their own element symbol with D or T.

To name compounds of different elements with each other, the element names are partially modified and provided with suffixes. For this we use the element roots in the following table, derived from the Latin or Greek element name. For example, the oxygen in the compound aluminum oxide ( Al2O3) by its root element (ox) and the suffix- id is specified.

Main group elements

Transition elements

Inorganic compounds of formulas

When writing formulas of chemical compounds are essentially follows the electronegativity of the chemical elements. It always starts with the electropositive partner connection, so you might write AgCl, Al2O3, PCl5, and not vice versa.

An exception to this rule are the hydrogen compounds. Are hydrogen atoms in the formulas to write in the last position (NH3, SiH4, etc.). If it is, however, to acidic hydrogen ( that is, the compound reacts in aqueous solution is acidic ), one writes the hydrogen at the beginning of the formula (HF, HCl, HBr, HI, H2O, H2O2, H2S, H2Se, H2Te ). In naming these compounds and the particular in the lab much more common name hydrogen fluoride or hydrogen chloride, for example, next to the name " hydrogen fluoride " for HF or " hydrogen chloride " for HCl used. The latter are to be preferred because of the clearer designation as a whole, since it does not concern salts with the corresponding anions in these compounds, but due to the high Elektronegativitätszahlen only partially loaded heavily Dipolverbindungen in which a strongly polar atomic bond is present ( covalent bond ). It should also be observed due to the ambiguity in naming, that means for example under " hydrogen fluoride " salts of the type MHF or MF × HF ( M = monovalent metal ), thus hydrogen fluoride is the preferred method. Even with inorganic oxo acids to write the hydrogen at the beginning of the formula, though he is actually bonded to the oxygen, so for sulfuric acid as H2SO4 instead of SO2 ( OH ) 2

Cations ( even formal ) basically keep the element name. Anions get their name systematically after the acid from which they are derived, regardless of whether it is in fact an ionic bond or covalent bond. The nomenclature for coordination compounds, ie complexes, does a little more complicated and is described there in more detail.

Anions of hydrogen acids

The simplest are the anions of hydrogen acids. With them after the submission of the proton Elementanion remains.

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

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

• SF6 sulfur hexafluoride

Oxide (O2 - ), sulfide (S2 - ), selenide ( Se2 ) example:

• Na2S Sodium sulfide

Nitride ( N3 - ), phosphide ( P3 ) example:

• Na3N sodium nitrite

Are rare example:

Oxygen or oxo acids and their anions

All entries except "id" are due to acids containing oxygen in addition to the eponymous element. Since there is a large amount of these compounds, the system is first explained and given the individual acids in a table at the end of the paragraph.

Element acids ( - at)

Here applies in general: Group 7: Halogen acid HXO3 eg chlorine acid HClO3 with the anion chlorate ( ClO3 - ) 6 main groups: Element H2XO4 acid eg sulfuric acid H2SO4 with the anion sulfate ( SO42 - ) Group 5: Element acid H3XO4 eg phosphoric acid H3PO4 with the anion phosphate ( PO43 - ); Exception: nitric acid 4 main groups: Element acid H2XO3 eg carbon acid ( carbonic acid) H2CO3 with the anion carbonate ( CO32 - ) 3 main groups: Element acid H3XO3 eg boric acid H3BO3 with the anion borate ( BO33 - )

Per- acids ( per ... - at)

These acids have in addition an oxygen atom. They are not all oxygen acids, but if they are formed, the oxidation state of the element is increased relative to the oxygen acid. Mainly, these acids are formed by the halogens:

Group 7: Perhalogen HXO4 eg perchloric acid HClO4 with the anion perchlorate ( ClO4 - )

" Elementige " acids ( -it )

These acids have an oxygen atom less than the element acids. For example, nitrous acid HNO 2 with the anion nitrite (NO2 - ), chlorous acid HClO2 with the anion chlorite ( ClO2 - ), sulphurous acid H2SO3 with the anions hydrogen sulfite ( HSO3 - ) and sulfite ( SO32 - ).

" Hypoelementige " acids ( hypo -it ... )

These acids have an oxygen atom is less than membered acids, such as hypochlorous acid HClO with the hypochlorite anion ( CIO ).

A plurality of oxidation states of the electro- positive partner

If there are several oxidation states for a metal atom to the present in a compound oxidation state is indicated by a trailing, in brackets, roman numeral. For example, iron ( II) oxide = FeO or iron ( III) oxide = Fe2O3

Complex anions

There are also guidelines for naming of complexes, which are explained in the article Coordination Chemistry.

Radical

To name the radical to the root name the suffix- yl is appended. This is true in both the organic and the inorganic chemistry.

Examples: HO •: hydroxyl (strain: Hydrox - ) CH3 •: methyl (strain: Meth )

Some radicals, particularly the oxygen compounds, special names.

Salt hydrates

Classification by structure

List of oxo acids and anions

Organic chemistry

For the naming of organic compounds in the IUPAC system conventionally starts from a root system that takes may have other substituents (radicals ). A substituent is an atom or an atomic combination, which replaces a hydrogen atom of the parent system ( group). For the designation of the connection, the name of the root system remains unchanged and the names of the substituting groups are the root system in a modified form attached ( substitutive nomenclature ).

Root systems

Linear chains

The simplest root systems are linear chains of carbon atoms in which all remaining bonds are saturated with hydrogen atoms. Such saturated hydrocarbons called alkanes, they get to the ending-. For the four smallest alkanes names methane, ethane, propane and butane are retained for other alkanes, the exact name of the compound obtained according to the following table of the number of carbon atoms. It combines the numeral of the first decade with the number of words for the following decades. In the end, followed by an n, so we obtain the typical alkane suffix- on.

Examples:

• C32H66 = dotriacontane ( Do Triaconta n)
• C99H200 = Nonanonacontan ( Nona Nonaconta n)
• C403H808 = Tritetractan ( Tri Tetracta n)
• C4728H9458 = Octacosaheptactatetralian ( octa Cosa Heptacta Tetralia n)
• C9999H20000 = Nonanonacontanonactanonalian ( Nona Nonaconta Nonacta nonalia n)

Exceptions to the designation referred to in the table above can be found at:

If a double bond in the compound is present, it is called alkenes and used instead of the ending- the ending- en. The position of the double bond is indicated by a number, see below in numbering, eg

• CH2 = CH- CH2-CH3 is, but-1 -ene ( formerly 1- butene )
• CH3 -CH = CH- CH3 is, but-2 -en.

For chains containing a triple bond ( alkynes = ), the ending- in is used, eg

• CH ≡ C- CH2-CH3 is but- 1-yne (formerly 1-butyne )
• CH2 = CH- CH2 -C ≡ C- CH2-CH3 is called hept -1 -en- 4-in.

If more double or triple bonds occur, use the multiplying prefixes di, tri, tetra penta, hexa, hepta, ...

• CH2 = CH -CH = CH2 so called buta-1 ,3-diene,
• CH ≡ C -C ≡ C -C ≡ C- CH3 is called hepta -1 ,3,5- Triin.

Determination of the main chain branched acyclic hydrocarbons at

The main chain (master system ) is that chain which

Note on locant:

A locant is the list of locants such as 2,4 in 2,4-dimethyl- heptane. The " lowest locant " does not mean now the smallest sum of locants, but comparing the locants sequentially. The smallest locant is the one that has the smaller locants at the first distinct place.

Cyclic systems without heteroatoms

In cyclic systems in general, a cycle is the root system.

Monocyclic systems

If it is a monocyclic compound, which designation is performed as the case of linear chains and, in addition, the prefix is prepended cycloalkyl, eg cyclohexane. For benzene, the trivial name is retained.

Monocyclic compounds having more than six C- atoms, which have the maximum number of noncumulative double bonds, can be designated as (n) annulenes ( n = number of C atoms).

Cyclic systems are preferably named after the Hantzsch - Widman system.

Condensed polycyclic systems

Wherein condensed polycyclic hydrocarbons (i.e., the individual rings are in each case via exactly one common bond linked) is the component of the base system, which

• Has the most rings
• Has the largest ring

The following polycyclic be construed as separate systems ( in ascending priority, in parentheses, the number of rings):

Pentalene (2) indene (2) naphthalene (2), azulene (2), heptalene (2) biphenyl ( 3), as- indacene (3), s- indacene (3), acenaphthylene (3), fluorene (3), phenalene (3), phenanthrene (3), anthracene (3), fluoranthene (4) Acephenanthrylen (4), aceanthrylene (4), triphenylene ( 4), and pyrene (4), chrysene (4) naphthacene (4), pleiadene (Chemistry ) (4), picene (5), perylene (5), pentaphene (5), pentacene (5), tetraphenylene (5) Hexaphen (6), hexacene (6), rubicene (7 ), coronene (7) Trinaphthylen (7) Heptaphen (7), heptacene (7), pyranthrene (8), an oval (10).

All other rings are preceded by a prefix, the suffix -ene is converted into - eno (eg benzocyclooctene ). The nature of the link is indicated by numbers and letters, which is not to be explained in more detail here.

To name saturated or partially saturated derivatives of the above polycyclic there is the possibility of the elimination of a double bond the two additional hydrogen atoms with the item numbers and the prefix dihydro- view. Similarly, there is tetrahydro-, hexahydro-, etc. Fully saturated systems receive the prefix - perhydro. Individual hydrogen atoms are indicated by the so-called indexed H which is prefixed in italics (eg 4H- pyrazole ).

Cyclophanes can be named by the same rules, although there is also a separate nomenclature for this.

Bridged polycyclic systems

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

Spiro compounds

In spiro compounds, the rings on a common atom are connected. Nomenclature: Substituents -spiro [number of atoms in the smaller ring. Number of atoms in the greater ring ] Family Name ( ring size is specified without a spiro atom). For example, 1 -bromo -3-chloro -spiro [4.5 ] decan -7 -ol.

More complicated systems

The determination of what is now considered as the root system is no longer easy for more complex compounds.

Heterocycles

If there are no trivial names, renames one monocyclic heterocycles with up to 10 ring members, usually after the Hantzsch - Widman system.

In condensed polycyclic heterocycles have priority over carbocycles ( = rings, which consist only of carbon atoms). Also for heterocycles there is on systems with trivial names, which are regarded as separate master systems (without stringing and incomplete):

• O- containing compounds: furan, xanthene, ...
• N-containing compounds: pyrrole, imidazole, pyrazole, ...

Otherwise the appointment of heterocycles largely follows the above rules for cyclic systems without heteroatoms. The nature and position of the hetero atoms is then specified using the replacement nomenclature or "a " nomenclature.

Substituents (radicals )

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

If there are multiple prefixes ( prefixes ), they will be listed in alphabetical order.

Root systems as substituents

If it is in turn the rest being a root system, for example, a side chain or a ring, the syllable -yl whose name is appended and prepended to the result as a prefix (prefix ). The naming of side chains according to the same rules as the backbone, with the following exceptions:

• Alkanes in the ending- at is omitted
• The numbering of the page always starts at the link chain to the main chain

Examples:

• Methyl: - CH3
• Ethyl: - CH2-CH3
• Ethinyl: -C ≡ CH
• Prop-2- enyl (allyl): -CH2-CH = CH2
• Cyclohexyl: - C6H11

If you are in the middle still clings for example, the compound propane (CH3 - CH2-CH3 ) a methane component, ie, the resulting compound CH3 -CH ( CH3) -CH 3 then 2-methyl propane. The compound CH3 -CH2-CH (CH3) -CH2-CH ( CH2CH3 ) - CH2-CH3 is 3-ethyl -5- methylheptane.

Side chains with double connection to the backbone receive the ending -ylene ( methylene: = CH2) with a triple - link ylidine ( methylidyne: ≡ CH).

Functional groups

The highest-ranking functional group is employed as an extension ( suffix) rear, other functional groups prefixed as prefixes ( prefixes ):

• CH3 -CH ( OH) - CH3 means propan-2 -ol
• CH3 -CH2-CH2 -C (OOH ) is called butanoic acid
• CH3 -CH ( OH) -CH2-CH (NH2) - CH2-CH3 having two functional groups. The alcohol has a higher priority, so to say the compound 4- amino-2 -hexanol.

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

Trivial names

For some substituents, there are trivial names, which are also partly authentic. For example:

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

Numbering

The numbering of the root system is such that the numbers obtained are as small as possible. CH3 -CH2-CH2 -CH ( CH3) - CH3 means that is 2-methyl pentane, and not 4-methyl pentane.

If there is only one possible combination of the numbers may be omitted (for example, 2-methyl propane = methyl propane, as there are no other methyl propane).

If side chains must be numbered, connecting the position is to the main chain is always 1

For naturally occurring derivatives of glycerol applies the sn- nomenclature for numbering of the carbon atoms according to IUPAC.

In condensed polycyclic systems possibly exist mandatory numbering schemes, which must each be like ( see, eg, sterane skeleton ).

The item numbers are called locants.

Multiple occurring substituents

For multiple occurrences of the same groups are the multiplying prefixes di, tri, tetra, penta, hexa, hepta, ... ( see above):

• A benzene ring with three methyl groups, at positions 1, 3 and 5 is 1,3,5- trimethylbenzene,
• A methane four chlorine atoms is carbon tetrachloride.
• An ether having two ethyl groups called diethyl ether, etc.

If the use of di-, tri, tetra, etc., would be misleading, as under identical further substituted side chains, must be as described above, the corresponding alternative prefixes bis, tris, tetrakis, and so on used. For directly linked identical units the prefixes are bi, ter, quater, etc. in use.

Example

According to IUPAC nomenclature must, for example, the connection

NH2 -CH2-CH2 -OH

Get the name of 2 -aminoethanol.

Here is how you get to this name:

Stereochemistry

Chiral compounds

To distinguish between chiral compounds, there is the italicized prefixes (R) - and (S) -. Their use is determined by the Cahn -Ingold- Prelog rule (CIP rule) and their side rules set. . , When a chiral compound as a 1:1 mixture of enantiomers - that is a racemate - to use the prefix (RS) -. When a stereo center uniformly present in a chiral compound, but for some reason the configuration ( R) - or (S) - is unclear, one used as a prefix ( Ξ ) - ( Greek letter Xi).

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

To distinguish the direction of rotation in optically active compounds using the prefixes ( ) - and (- ) -, with no correlation between the optical activity (direction of rotation ) and the " direction " chirality exists.

It should be noted that the different notations (R, S or D, L, , -) can not be derived from each other names according to the different types of nomenclature. For the systematic designation of compounds with multiple chiral centers, only the CIP rules are useful, with the Fischer nomenclature is much more compact, for example, sugar.

Cis -trans isomers

In the cis- trans isomerism, a distinction in nomenclature between compounds that have only two different substituents, and compounds with more than two. The former are cis -or trans- identified by the italicized prefixes. cis double bonds are usually - but not consistently - after IUPAC preceded by, italic (Z ) ( "Together " ) and trans double bonds marked with an (E ) ( " Opposite "). Strictly speaking, are in a (Z)- isomer, that two substituents on adjacent atoms of the double bond on the same side of the molecule, which have the highest priority in the Cahn-Ingold- Prelog system, the (E)- isomer of the substituents with the highest thus, CIP priority on opposite sides of the molecule.

Links is the trans -1 ,2- dibromoethene, shown at right, the cis version. Here also one can use the (E, Z)- nomenclature, trans-1 ,2- dibromoethene is referred to as (E ) -1,2- dibromoethene, " cis " and (Z ) -1,2- dibromoethene.

Again, the two bromine atoms in trans ( left) and cis ( "Together " on one side ) are shown on the ring.

This is a (Z )-3- methylpent -2-ene, as the higher-ranked substituent (see stereochemistry) are on one side.

Anomers

For carbohydrates, a distinction anomers by the italicized prefixes α - or β -.

Biochemistry

For the nomenclature of enzymes, there are common guidelines of IUPAC and IUBMB (International Union of Biochemistry and Molecular Biology). According to this nomenclature enzyme name -ase and contain information about the function of the enzyme. Details under the heading of enzyme and on the website of the IUBMB.

In addition, a code system (see EC numbers ) was developed, in which the enzymes are found under a numerical code of four digits.

For nucleic acids, the nucleic acid nomenclature will apply.

Chemical nomenclature outside the IUPAC rules

• For plastic labels, there are defined by a DIN standard abbreviations.
• Food additives, there is the system of E-numbers.