The numerical multiplier (or multiplying affix) in IUPAC nomenclature indicates how many particular atoms or functional groups are attached at a particular point in a molecule. The affixes are derived from both Latin and Greek.
Contents
Compound affixes
The affix for a number larger than twelve is constructed in the opposite order to that which the number is written in Hindu-Arabic numerals: 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, it is often essential in inorganic chemistry to avoid ambiguity: carbon oxide could refer to either carbon monoxide or carbon dioxide. 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 prefers the spelling icosa- for the affix corresponding to the number twenty on the grounds of etymology. However both the Chemical Abstracts Service and the Beilstein database use the alternative spelling eicosa-.
Etymology
"mono-" is from Greek monos = "alone". "un" = 1 and "nona-" = 9 are from Latin. The others are derived from Greek numbers.
Linguists should note that the forms 100 and upwards are not correct Greek. In Ancient 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., and 13 to 19 are treiskaideka etc. with the Greek for "and" inserted (as in triskaidekaphobia).