Thenumerical multiplier (ormultiplying affix) inIUPAC nomenclature indicates how many particularatoms orfunctional groups are attached at a particular point in amolecule. Theaffixes are derived from bothLatin andGreek.

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-

While the use of the affixmono- is rarely necessary inorganic chemistry, it is often essential ininorganic chemistry to avoid ambiguity:carbon oxide could refer to eithercarbon monoxide orcarbon dioxide. In forming compound affixes, the numeral one is represented by the termhen- 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-

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

IUPAC prefers the spellingicosa- for the affix corresponding to the number twenty on the grounds ofetymology. However both theChemical Abstracts Service and theBeilstein database use the alternative spellingeicosa-.

There are two more types of numerical prefixes in IUPAC organic chemistry nomenclature.^[1]

Numerical prefixes for multiplication of compound or complex (as incomplicated) features are created by addingkis 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 forDDT (1,1,1-Trichloro-bis-2,2(4-chlorophenyl)ethane).

Examples arebiphenyl orterphenyl.

"mono-" is fromGreekmonos = "alone". "un" = 1 and "nona-" = 9 are fromLatin. The others are derived from Greek numbers.

The forms 100 and upwards are not correct Greek. InAncient Greek,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.

13 to 19 are formed by starting with the Greek word for the number of ones, followed byκαι (the Greek word for 'and'), followed byδέκα (the Greek word for 'ten'). For instancetreiskaideka, as intriskaidekaphobia.

• Panico, R. & Powell, W. H., eds. (1994).A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science.ISBN 0-632-03488-2.

• Chemical nomenclature

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