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In
chemical nomenclature A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC). Th ...
, the IUPAC nomenclature of organic chemistry is a method of naming organic chemical compounds as recommended by the
International Union of Pure and Applied Chemistry The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
(IUPAC). It is published in the '' Nomenclature of Organic Chemistry'' (informally called the Blue Book). Ideally, every possible organic compound should have a name from which an unambiguous
structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bond ...
can be created. There is also an IUPAC nomenclature of inorganic chemistry. To avoid long and tedious names in normal communication, the official IUPAC naming recommendations are not always followed in practice, except when it is necessary to give an unambiguous and absolute definition to a compound. IUPAC names can sometimes be simpler than older names, as with
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
, instead of ethyl alcohol. For relatively simple molecules they can be more easily understood than non-systematic names, which must be learnt or looked over. However, the common or
trivial name In chemistry, a trivial name is a non systematic name for a chemical substance. That is, the name is not recognized according to the rules of any formal system of chemical nomenclature such as IUPAC inorganic or IUPAC organic nomenclature. A ...
is often substantially shorter and clearer, and so preferred. These non-systematic names are often derived from an original source of the compound. Also, very long names may be less clear than structural formulas.


Basic principles

In chemistry, a number of
prefix A prefix is an affix which is placed before the stem of a word. Adding it to the beginning of one word changes it into another word. For example, when the prefix ''un-'' is added to the word ''happy'', it creates the word ''unhappy''. Particul ...
es, suffixes and
infix An infix is an affix inserted inside a word stem (an existing word or the core of a family of words). It contrasts with '' adfix,'' a rare term for an affix attached to the outside of a stem, such as a prefix or suffix. When marking text for i ...
es are used to describe the type and position of the
functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...
s in the compound. The steps for naming an organic compound are: # Identification of the parent hydrocarbon chain. This chain must obey the following rules, in order of precedence: ## It should have the maximum number of substituents of the suffix functional group. By suffix, it is meant that the parent functional group should have a suffix, unlike halogen substituents. If more than one functional group is present, the one with highest group precedence should be used. ## It should have the maximum number of multiple bonds. ##It should have the maximum length. ## It should have the maximum number of substituents or branches cited as prefixes ## It should have the maximum number of single bonds. # Identification of the parent
functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...
, if any, with the highest order of precedence. # Identification of the side-chains. Side chains are the carbon chains that are not in the parent chain, but are branched off from it. # Identification of the remaining functional groups, if any, and naming them by their ionic prefixes (such as hydroxy for -OH, oxy for =O, oxyalkane for O-R, etc.).
Different side-chains and functional groups will be grouped together in alphabetical order. (The prefixes di-, tri-, etc. are not taken into consideration for grouping alphabetically. For example, ethyl comes before dihydroxy or dimethyl, as the "e" in "ethyl" precedes the "h" in "dihydroxy" and the "m" in "dimethyl" alphabetically. The "di" is not considered in either case). When both side chains and secondary functional groups are present, they should be written mixed together in one group rather than in two separate groups. # Identification of double/triple bonds. # Numbering of the chain. This is done by first numbering the chain in both directions (left to right and right to left), and then choosing the numbering which follows these rules, in order of precedence. ## Has the lowest-numbered locant (or locants) for the suffix functional group. Locants are the numbers on the carbons to which the substituent is directly attached. ## Has the lowest-numbered locants for multiple bonds (The locant of a multiple bond is the number of the adjacent carbon with a lower number). ## Has the lowest-numbered locants for prefixes. # Numbering of the various substituents and bonds with their locants. If there is more than one of the same type of substituent/double bond, a prefix is added showing how many there are (di – 2 tri – 3 tetra – 4 then as for the number of carbons below with 'a' added) The numbers for that type of side chain will be grouped in ascending order and written before the name of the side-chain. If there are two side-chains with the same alpha carbon, the number will be written twice. Example: 2,2,3-trimethyl- . If there are both double bonds and triple bonds, "en" (double bond) is written before "yne" (triple bond). When the main functional group is a terminal functional group (a group which can exist only at the end of a chain, like formyl and carboxyl groups), there is no need to number it. # Arrangement in this form: Group of side chains and secondary functional groups with numbers made in step 3 + prefix of parent hydrocarbon chain (eth, meth) + double/triple bonds with numbers (or "ane") + primary functional group suffix with numbers.
Wherever it says "with numbers", it is understood that between the word and the numbers, the prefix (di-, tri-) is used. # Adding of punctuation: ## Commas are put between numbers (2 5 5 becomes 2,5,5) ## Hyphens are put between a number and a letter (2 5 5 trimethylheptane becomes 2,5,5-trimethylheptane) ## Successive words are merged into one word (trimethyl heptane becomes trimethylheptane)
Note: IUPAC uses one-word names throughout. This is why all parts are connected. The resulting name appears as: :#,#-di<side chain>-#-<secondary functional group>-#-<side chain>-#,#,#-tri<secondary functional group><parent chain prefix><If all bonds are single bonds, use "ane">-#,#-di<double bonds>-#-<triple bonds>-#-<primary functional group> where each "#" represents a number. The group secondary functional groups and side chains may not look the same as shown here, as the side chains and secondary functional groups are arranged alphabetically. The di- and tri- have been used just to show their usage. (di- after #,#, tri- after #,#,#, etc.)


Example

Here is a sample molecule with the parent carbons numbered: For simplicity, here is an image of the same molecule, where the hydrogens in the parent chain are removed and the carbons are shown by their numbers: Now, following the above steps: # The parent hydrocarbon chain has 23 carbons. It is called tricosa-. # The functional groups with the highest precedence are the two ketone groups. ## The groups are on carbon atoms 3 and 9. As there are two, we write 3,9-dione. ## The numbering of the molecule is based on the ketone groups. When numbering from left to right, the ketone groups are numbered 3 and 9. When numbering from right to left, the ketone groups are numbered 15 and 21. 3 is less than 15, therefore the ketones are numbered 3 and 9. The smaller number is always used, not the sum of the constituents numbers. # The side chains are: an ethyl- at carbon 4, an ethyl- at carbon 8, and a butyl- at carbon 12.
Note: the at carbon atom 15 is not a side chain, but it is a methoxy functional group. #* There are two ethyl- groups. They are combined to create, 4,8-diethyl. #* The side chains are grouped like this: 12-butyl-4,8-diethyl. (But this is not necessarily the final grouping, as functional groups may be added in between to ensure all groups are listed alphabetically.) # The secondary functional groups are: a hydroxy- at carbon 5, a chloro- at carbon 11, a methoxy- at carbon 15, and a bromo- at carbon 18. Grouped with the side chains, this gives 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxy. # There are two double bonds: one between carbons 6 and 7, and one between carbons 13 and 14. They would be called "6,13-diene", but the presence of alkynes switches it to 6,13-dien. There is one triple bond between carbon atoms 19 and 20. It will be called 19-yne. # The arrangement (with punctuation) is: 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricosa-6,13-dien-19-yne-3,9-dione # Finally, due to cis-trans isomerism, we have to specify the relative orientation of functional groups around each double bond. For this example, both double bonds are trans isomers, so we have (6''E'',13''E'') The final name is (6''E'',13''E'')-18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricosa-6,13-dien-19-yne-3,9-dione.


Hydrocarbons


Alkanes

Straight-chain alkanes take the suffix "
-ane The suffix -ane in organic chemistry forms the names of organic compounds where the -C-C- group has been attributed the highest priority according to the rules of organic nomenclature. Such organic compounds are called alkanes. They are saturate ...
" and are prefixed depending on the number of carbon atoms in the chain, following standard rules. The first few are: For example, the simplest alkane is methane, and the nine-carbon alkane is named
nonane Nonane is a linear alkane hydrocarbon with the chemical formula C9H20. It is a colorless, flammable liquid, occurring primarily in the component of the petroleum distillate fraction commonly called kerosene, which is used as a heating, tractor, a ...
. The names of the first four alkanes were
derived Derive may refer to: *Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguation ...
from
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is ...
,
ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again ...
,
propionic acid Propionic acid (, from the Greek words πρῶτος : ''prōtos'', meaning "first", and πίων : ''píōn'', meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2CO2H. It is a li ...
and
butyric acid Butyric acid (; from grc, βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, is a straight-chain alkyl carboxylic acid with the chemical formula CH3CH2CH2CO2H. It is an oily, colorless liquid with an unp ...
, respectively. The rest are named with a Greek numeric prefix, with the exceptions of nonane which has a
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
prefix, and undecane which has mixed-language prefixes. Cyclic alkanes are simply prefixed with "cyclo-": for example, is cyclobutane (not to be confused with
butene Butene, also known as butylene, is an alkene with the formula . The word ''butene'' may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for ...
) and is
cyclohexane Cyclohexane is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohe ...
(not to be confused with hexene).
Branched alkanes are named as a straight-chain alkane with attached
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
groups. They are prefixed with a number indicating the carbon the group is attached to, counting from the end of the alkane chain. For example, , commonly known as
isobutane Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colourless, odourless gas. It is the simplest alkane with a tertiary carbo ...
, is treated as a propane chain with a methyl group bonded to the middle (2) carbon, and given the systematic name 2-methylpropane. However, although the name 2-methylpropane ''could'' be used, it is easier and more logical to call it simply methylpropane – the methyl group could not possibly occur on any of the other carbon atoms (that would lengthen the chain and result in butane, not propane) and therefore the use of the number "2" is unnecessary. If there is ambiguity in the position of the substituent, depending on which end of the alkane chain is counted as "1", then numbering is chosen so that the smaller number is used. For example, (isopentane) is named 2-methylbutane, not 3-methylbutane. If there are multiple side-branches of the same size alkyl group, their positions are separated by commas and the group prefixed with di-, tri-, tetra-, etc., depending on the number of branches. For example, (neopentane) is named 2,2-dimethylpropane. If there are different groups, they are added in alphabetical order, separated by commas or hyphens. The longest possible main alkane chain is used; therefore 3-ethyl-4-methylhexane instead of 2,3-diethylpentane, even though these describe equivalent structures. The di-, tri- etc. prefixes are ignored for the purpose of alphabetical ordering of side chains (e.g. 3-ethyl-2,4-dimethylpentane, not 2,4-dimethyl-3-ethylpentane).


Alkenes

Alkenes are named for their parent alkane chain with the suffix " -ene" and an infixed number indicating the position of the carbon with the lower number for each double bond in the chain: is but-1-ene. Multiple double bonds take the form -diene, -triene, etc., with the size prefix of the chain taking an extra "a": is buta-1,3-diene. Simple cis and trans
isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. ...
may be indicated with a prefixed ''cis-'' or ''trans-'': ''cis''-but-2-ene, ''trans''-but-2-ene. However, ''cis-'' and ''trans-'' are ''relative'' descriptors. It is IUPAC convention to describe all alkenes using ''absolute'' descriptors of ''Z-'' (same side) and ''E-'' (opposite) with the Cahn–Ingold–Prelog priority rules.


Alkynes

Alkynes are named using the same system, with the suffix "
-yne In chemistry, the suffix -yne is used to denote the presence of a triple bond. The suffix follows IUPAC nomenclature, and is mainly used in organic chemistry. However, inorganic compounds featuring unsaturation in the form of triple bonds may b ...
" indicating a triple bond: ethyne (
acetylene Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
), propyne (
methylacetylene Propyne (methylacetylene) is an alkyne with the chemical formula . It is a component of MAPD gas—along with its isomer propadiene (allene), which was commonly used in gas welding. Unlike acetylene, propyne can be safely condensed.Peter P� ...
).


Functional groups


Haloalkanes and haloarenes

In Haloalkanes and Haloarenes (R-X),
Halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this grou ...
functional groups are prefixed with the bonding position and take the form of fluoro-, chloro-, bromo-, iodo-, etc., depending on the halogen. Multiple groups are dichloro-, trichloro-, etc., and dissimilar groups are ordered alphabetically as before. For example, (
chloroform Chloroform, or trichloromethane, is an organic compound with formula C H Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to PTFE. It is also a precursor to various ...
) is trichloromethane. The anesthetic halothane () is 2-bromo-2-chloro-1,1,1-trifluoroethane.


Alcohols

Alcohols (R-OH) take the suffix " -ol" with an infix numerical bonding position: is propan-1-ol. The suffixes , , , etc., are used for multiple -OH groups:
Ethylene glycol Ethylene glycol ( IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an o ...
is ethane-1,2-diol. If higher precedence functional groups are present (see ''
order of precedence An order of precedence is a sequential hierarchy of nominal importance and can be applied to individuals, groups, or organizations. Most often it is used in the context of people by many organizations and governments, for very formal and state o ...
'', below), the prefix "hydroxy" is used with the bonding position: is 2-hydroxypropanoic acid.


Ethers

Ethers (R-O-R) consist of an oxygen atom between the two attached carbon chains. The shorter of the two chains becomes the first part of the name with the -ane suffix changed to -oxy, and the longer alkane chain becomes the suffix of the name of the ether. Thus, is methoxymethane, and is
methoxyethane Methoxyethane, also known as ethyl methyl ether, is a colorless gaseous ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general f ...
(''not'' ethoxymethane). If the oxygen is not attached to the end of the main alkane chain, then the whole shorter alkyl-plus-ether group is treated as a side-chain and prefixed with its bonding position on the main chain. Thus is 2-methoxypropane. Alternatively, an ether chain can be named as an alkane in which one carbon is replaced by an oxygen, a replacement denoted by the prefix "oxa". For example, could also be called 2-oxabutane, and an
epoxide In organic chemistry, an epoxide is a cyclic ether () with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. They are produced on a large scale ...
could be called oxacyclopropane. This method is especially useful when both groups attached to the oxygen atom are complex.


Aldehydes

Aldehydes (R-CHO) take the suffix "
-al In chemistry, the suffix -al is the IUPAC nomenclature used in organic chemistry to form names of aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itse ...
". If other functional groups are present, the chain is numbered such that the aldehyde carbon is in the "1" position, unless functional groups of higher precedence are present. If a prefix form is required, "oxo-" is used (as for ketones), with the position number indicating the end of a chain: is 3-oxopropanoic acid. If the carbon in the carbonyl group cannot be included in the attached chain (for instance in the case of cyclic aldehydes), the prefix "formyl-" or the suffix "-carbaldehyde" is used: is cyclohexanecarbaldehyde. If an aldehyde is attached to a benzene and is the main functional group, the suffix becomes benzaldehyde.


Ketones

In general ketones (R-CO-R) take the suffix " -one" (pronounced ''own'', not ''won'') with an infix position number: is pentan-2-one. If a higher precedence suffix is in use, the prefix "oxo-" is used: is 3-oxohexanal.


Carboxylic acids

In general, carboxylic acids are named with the suffix '' -oic acid'' (etymologically a
back-formation In etymology, back-formation is the process or result of creating a new word via inflection, typically by removing or substituting actual or supposed affixes from a lexical item, in a way that expands the number of lexemes associated with the ...
from
benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin ...
). As with aldehydes, the
carboxyl In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
functional group must take the "1" position on the main chain and so the locant need not be stated. For example, (
lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as nat ...
) is named 2-hydroxypropanoic acid with no "1" stated. Some traditional names for common carboxylic acids (such as
acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...
) are in such widespread use that they are
retained In the United Kingdom and Ireland, a retained firefighter, also known as an RDS Firefighter or on-call firefighter, is a firefighter who does not work on a fire station full-time but is paid to spend long periods of time on call to respond to eme ...
in IUPAC nomenclature, though systematic names like ethanoic acid are also used. Carboxylic acids attached to a benzene ring are
structural analog A structural analog (analogue in modern traditional English; Commonwealth English), also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a c ...
s of benzoic acid ( Ph-COOH) and are named as one of its derivatives. If there are multiple carboxyl groups on the same parent chain, multiplying prefixes are used:
Malonic acid Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH2(COOH)2. The ionized form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid' ...
, , is systematically named propanedioic acid. Alternatively, the suffix can be used, combined with a multiplying prefix if necessary –
mellitic acid Mellitic acid, also called graphitic acid or benzenehexacarboxylic acid, is an acid first discovered in 1799 by Martin Heinrich Klaproth in the mineral mellite (honeystone), which is the aluminium salt of the acid. It crystallizes in fine silky ne ...
is benzenehexacarboxylic acid, for example. In the latter case, the carbon atoms in the carboxyl groups do ''not'' count as being part of the main chain, a rule that also applies to the prefix form "carboxy-".
Citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...
serves as an example: it is formally named rather than .


Carboxylates

Salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...
of carboxylic acids are named following the usual
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
-then-
anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
conventions used for ionic compounds in both IUPAC and common nomenclature systems. The name of the carboxylate anion is derived from that of the parent acid by replacing the "–oic acid" ending with "–oate." For example, , the sodium salt of
benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin ...
(), is called sodium benzoate. Where an acid has both a systematic and a common name (like , for example, which is known as both
acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...
and as ethanoic acid), its salts can be named from either parent name. Thus, can be named as
potassium acetate Potassium acetate (CH3COOK) is the potassium salt of acetic acid. It is a hygroscopic solid at room temperature. Preparation It can be prepared by treating a potassium-containing base such as potassium hydroxide or potassium carbonate with acetic ...
or as potassium ethanoate.


Esters

Esters (R-CO-O-R') are named as alkyl derivatives of carboxylic acids. The alkyl (R') group is named first. The R-CO-O part is then named as a separate word based on the carboxylic acid name, with the ending changed from ''-oic acid'' to '' -oate''. For example, is ''methyl pentanoate'', and is ''ethyl 4-methylpentanoate''. For esters such as
ethyl acetate Ethyl acetate ( systematically ethyl ethanoate, commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues ...
(),
ethyl formate Ethyl formate is an ester formed when ethanol (an alcohol) reacts with formic acid (a carboxylic acid). Ethyl formate has the characteristic smell of rum and is also partially responsible for the flavor of raspberries. It occurs naturally in the b ...
() or dimethyl phthalate that are based on common acids, IUPAC recommends use of these established names, calle
retained names
The ''-oate'' changes to ''-ate''. Some simple examples, named both ways, are shown in the figure above. If the alkyl group is not attached at the end of the chain, the bond position to the ester group is infixed before "-yl": may be called butan-2-yl propanoate or butan-2-yl propionate.


Acyl groups

Acyl groups are named by stripping the -ic acid of the corresponding carboxylic acid and replacing it with -yl. For Example, CH3CO-R is called Ethanoyl-R.


Acyl halides

Simply add the name of the attached halide to the end of the acyl group. For example, CH3COCl is ethanoyl chloride.


Acid anhydrides

Acid anhydrides (R-CO-O-OC-R) have two acyl groups linked by an oxygen atom. If both acyl groups are the same, then the name of the carboxylic acid with the word acid is replaced with the word ''anhydride'' and the IUPAC name consists of two words. If the acyl groups are different, then they are named in alphabetical order in the same way, with ''anhydride'' replacing ''acid'' and IUPAC name consists of three words. For example, is called ''ethanoic anhydride'' and is called ''ethanoic propanoic anhydride''.


Amines

Amines () are named for the attached alkane chain with the suffix "-amine" (e.g., methanamine). If necessary, the bonding position is infixed: propan-1-amine, propan-2-amine. The prefix form is "amino-". For secondary amines (of the form R-NH-R), the longest carbon chain attached to the nitrogen atom becomes the primary name of the amine; the other chain is prefixed as an alkyl group with location prefix given as an italic ''N'': is ''N''-methylethanamine. Tertiary amines () are treated similarly: is ''N''-ethyl-''N''-methylpropanamine. Again, the substituent groups are ordered alphabetically.


Amides

Amides () take the suffix "-amide", or "-carboxamide" if the carbon in the amide group cannot be included in the main chain. The prefix form is both "carbamoyl-" and "amido-", e.g., methanamide, ethanamide. Amides that have additional substituents on the nitrogen are treated similarly to the case of amines: they are ordered alphabetically with the location prefix ''N'': is ''N'',''N''-dimethylmethanamide, is ''N'',''N''-dimethylethanamide.


Nitriles

Nitriles (RCN) are named by adding the suffix -nitrile to the longest hydrocarbon chain (including the carbon of the cyano group). It can also be named by replacing the -oic acid of their corresponding carboxylic acids with -onitrile. Functional class IUPAC nomenclature may also be used in the form of alkyl cyanides. For example, CH3CH2CH2CH2C#N is called pentanenitrile or butyl cyanide.


Cyclic compounds

Cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containin ...
s and
aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
compounds can be treated as the main parent chain of the compound, in which case the positions of substituents are numbered around the ring structure. For example, the three isomers of
xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...
, commonly the ''ortho-'', ''meta-'', and ''para-'' forms, are 1,2-dimethylbenzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene. The cyclic structures can also be treated as functional groups themselves, in which case they take the prefix "cyclo''alkyl''-" (e.g. "cyclohexyl-") or for benzene, "phenyl-". The IUPAC nomenclature scheme becomes rapidly more elaborate for more complex cyclic structures, with notation for compounds containing conjoined rings, and many common names such as
phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it r ...
being accepted as base names for compounds derived from them.


Order of precedence of group

When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The table below shows common groups in decreasing order of precedence. The highest-precedence group takes the suffix, with all others taking the prefix form. However, double and triple bonds only take suffix form (-en and -yn) and are used with other suffixes. Prefixed substituents are ordered alphabetically (excluding any modifiers such as di-, tri-, etc.), e.g. chlorofluoromethane, ''not'' fluorochloromethane. If there are multiple functional groups of the same type, either prefixed or suffixed, the position numbers are ordered numerically (thus ethane-1,2-diol, ''not'' ethane-2,1-diol.) The ''N'' position indicator for amines and amides comes before "1", e.g., is ''N'',2-dimethylpropanamine. *''Note'': These suffixes, in which the carbon atom is counted as part of the preceding chain, are the most commonly used. See individual functional group articles for more details. The order of remaining functional groups is only needed for substituted benzene and hence is not mentioned here.


Common nomenclature – trivial names

Common nomenclature uses the older names for some organic compounds instead of using the prefixes for the carbon skeleton above. The pattern can be seen below.


Ketones

Common names for
ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double b ...
s can be derived by naming the two
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
or
aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...
groups bonded to the
carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
as separate words followed by the word ''ketone''. *
Acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscibl ...
*
Acetophenone Acetophenone is the organic compound with the chemical formula, formula C6H5C(O)CH3. It is the simplest aromatic ketone. This colorless, viscous liquid is a precursor to useful resins and fragrances. Production Acetophenone is formed as a byprodu ...
*
Benzophenone Benzophenone is the organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylket ...
* Ethyl isopropyl ketone * Diethyl ketone The first three of the names shown above are still considered to b
acceptable IUPAC names


Aldehydes

The common name for an
aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl gro ...
is derived from the common name of the corresponding
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyli ...
by dropping the word ''acid'' and changing the suffix from -ic or -oic to -aldehyde. *
Formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
*
Acetaldehyde Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the ...


Ions

The IUPAC nomenclature also provides rules for naming ions.


Hydron

Hydron is a generic term for hydrogen cation; protons, deuterons and tritons are all hydrons. The hydrons are not found in heavier isotopes, however.


Parent hydride cations

Simple cations formed by adding a hydron to a hydride of a halogen,
chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioac ...
or pnictogen are named by adding the suffix "-onium" to the element's root: H4N+ is ammonium, H3O+ is oxonium, and H2F+ is fluoronium. Ammonium was adopted instead of nitronium, which commonly refers to NO2+. If the cationic center of the hydride is not a halogen, chalcogen or pnictogen then the suffix "-ium" is added to the name of the neutral hydride after dropping any final 'e'. H5C+ is methanium, HO-(O+)-H2 is dioxidanium (HO-OH is dioxidane), and H2N-(N+)-H3 is diazanium (H2N-NH2 is diazane).


Cations and substitution

The above cations except for methanium are not, strictly speaking, organic, since they do not contain carbon. However, many organic cations are obtained by substituting another element or some functional group for a hydrogen. The name of each substitution is prefixed to the hydride cation name. If many substitutions by the same functional group occur, then the number is indicated by prefixing with "di-", "tri-" as with halogenation. (CH3)3O+ is trimethyloxonium. CH3F3N+ is trifluoromethylammonium.


See also

* Descriptor (chemistry) *
Hantzsch–Widman nomenclature In organic chemistry, Hantzsch–Widman nomenclature, also called the extended Hantzsch–Widman system (named for Arthur Rudolf Hantzsch and ), is a type of systematic chemical nomenclature used for naming heterocyclic parent hydrides having no ...
* International Union of Biochemistry and Molecular Biology * Nucleic acid notation * Organic nomenclature in Chinese * Phanes *
Preferred IUPAC name In chemical nomenclature, a preferred IUPAC name (PIN) is a unique name, assigned to a chemical substance and preferred among the possible names generated by IUPAC nomenclature. The "preferred IUPAC nomenclature" provides a set of rules for choo ...
* Von Baeyer nomenclature * IUPAC nomenclature of inorganic chemistry


References


Bibliography

*


External links


IUPAC Nomenclature of Organic Chemistry
(online version of several older editions of the
IUPAC Blue Book ''Nomenclature of Organic Chemistry'', commonly referred to by chemists as the ''Blue Book'', is a collection of recommendations on organic chemical nomenclature published at irregular intervals by the International Union of Pure and Applied C ...
)
IUPAC Recommendations on Organic & Biochemical Nomenclature, Symbols, Terminology, etc.
(includes IUBMB Recommendations for biochemistry)

(last updated 11 April 2003)
ACD/Name
Software for generating systematic nomenclature
ChemAxon Name <> Structure
– ChemAxon IUPAC (& traditional) name to structure and structure to IUPAC name software. As used a
chemicalize.orgchemicalize.org
A free web site/service that extracts IUPAC names from web pages and annotates a 'chemicalized' version with structure images. Structures from annotated pages can also be searched. *

* {{Organic chemistry Chemical nomenclature Encodings Organic chemistry