IUPAC numerical multiplier

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Number	Multiplier	Number	Multiplier
1	mono-	32	dotriaconta-
2	di-	40	tetraconta-
3	tri-	50	pentaconta-
4	tetra-	60	hexaconta-
5	penta-	70	heptaconta-
6	hexa-	80	octaconta-
7	hepta-	90	nonaconta-
8	octa-	100	hecta-
9	nona-	200	dicta-
10	deca-	300	tricta-
11	undeca-	400	tetracta-
12	dodeca-	500	pentacta-
13	trideca-	600	hexacta-
14	tetradeca-	700	heptacta-
15	pentadeca-	800	octacata-
16	hexadeca-	900	nonacta-
17	heptadeca-	1000	kilia-
18	octadeca-	2000	dilia-
19	nonadeca-	3000	trilia-
20	icosa-^[1]	4000	tetralia-
21	henicosa-	5000	pentalia-
22	docosa-	6000	hexalia-
23	tricosa-	7000	heptalia-
30	triconta-	8000	octalia-
31	hentriconta-	9000	nonalia-

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.

1 Compound affixes
- 1.1 The numeral one
- 1.2 The numeral two
2 Icosa- v. eicosa-
3 Etymology
4 Source

[edit] Compound affixes

The affix for a number larger than twelve is constructed is 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-

[edit] 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-

[edit] 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-).

[edit] 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-.

[edit] 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, khīlioi = 1000, diskhīlioi = 2000, triskhīlioi = 3000, etc, and 13 to 19 are treiskaideka etc with the Greek for "and" inserted (as in triskaidekaphobia).