The numerical multiplier (or multiplying affix) in IUPAC nomenclature indicates how many particular atoms or

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 res ...

s are attached at a particular point in a

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

. The

affix In linguistics, an affix is a morpheme that is attached to a word stem to form a new word or word form. Affixes may be derivational, like English ''-ness'' and ''pre-'', or inflectional, like English plural ''-s'' and past tense ''-ed''. They ...

es are derived from both

Latin Latin (, or , ) is a classical language belonging to the 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 the power ...

and

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

Compound affixes

The prefixes are given from the least significant decimal digit up: units, then tens, then hundreds, then thousands. For example: :548 → octa- (8) + tetraconta- (40) + pentacta- (500) = ''octatetracontapentacta-'' :9267 → hepta- (7) + hexaconta- (60) + dicta- (200) + nonalia- (9000) = ''heptahexacontadictanonalia-''

The numeral one

While the use of the affix ''mono-'' is rarely necessary in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clay ...

, it is often essential in

inorganic chemistry Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disc ...

to avoid ambiguity: carbon oxide could refer to either ''

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

'' or ''

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

''. In forming compound affixes, the numeral one is represented by the term ''hen-'' except when it forms part of the number eleven (''undeca-''): hence :241 → hen- (1) + tetraconta- (40) + dicta- (200) = ''hentetracontadicta-'' :411 → undeca- (11) + tetracta- (400) = ''undecatetracta-''

The numeral two

In compound affixes, the numeral two is represented by ''do-'' except when it forms part of the numbers 20 (''icosa-''), 200 (''dicta-'') or 2000 (''dilia-'').

Icosa- ''v.'' eicosa-

IUPAC 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 ...

prefers the spelling icosa- for the affix corresponding to the number twenty on the grounds of

etymology Etymology () The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words ...

. However both the

Chemical Abstracts Service CAS (formerly Chemical Abstracts Service) is a division of the American Chemical Society. It is a source of chemical information. CAS is located in Columbus, Ohio, United States. Print periodicals ''Chemical Abstracts'' is a periodical index th ...

and the Beilstein database use the alternative spelling ''eicosa-''.

Other numerical prefix types

There are two more types of numerical prefixes in IUPAC organic chemistry nomenclature. IUPAC Blue Book, 2013

Numerical terms for compound or complex features

Numerical prefixes for multiplication of compound or complex (as in ''complicated'') features are created by adding ''kis'' to the basic numerical prefix, with the exception of numbers 2 and 3, which are bis- and tris-, respectively. An example is the IUPAC name for DDT.

Multiplicative prefixes for naming assemblies of identical units

Examples are biphenyl or

terphenyl Terphenyls are a group of closely related aromatic hydrocarbons. Also known as diphenylbenzenes or triphenyls, they consist of a central benzene ring substituted with two phenyl groups. There are three substitution patterns: ''ortho''-terpheny ...

Etymology

"mono-" is from

''monos'' = "alone". "un" = 1 and "nona-" = 9 are from

. The others are derived from Greek numbers. The forms 100 and upwards are not correct Greek. In

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

, ''hekaton'' = 100, ''diakosioi'' = 200, ''triakosioi'' = 300, etc. The numbers 200-900 would be confused easily with 22 to 29 if they were used in chemistry. ''khīlioi'' = 1000, ''diskhīlioi'' = 2000, ''triskhīlioi'' = 3000, etc., and 13 to 19 are ''treiskaideka'' etc. with the Greek for "and"inserted (as in

triskaidekaphobia Triskaidekaphobia ( , ; ) is fear or avoidance of the number . It is also a reason for the fear of Friday the 13th, called ''paraskevidekatriaphobia'' () or ''friggatriskaidekaphobia'' (). The term was used as early as in 1910 by Isador Coria ...

Notes and references

* {{Reflist, 2 Chemical nomenclature