notes on nomenclature tetra-ammine; as a substitute for enclosing marks; or for separating affixes: tetraammine-chlorohydroxocobalt(l+) ion. The hyphen is frequently confused with the dash which is used to indicate a bond in chemical formulas or to show the two components of a molecular compound. 2CHzOH.Bh
W. C. FERNELIUS
university of South Florida
KURT LOENING
Chemical Abstracts Service Columbus. Ohio 4 3 2 1 0
ROY M. ADAMS
Tompa 3 3 6 2 0
methanol-boron
trifluoride (2: 1)
Commas are used to separate locants, whether numbers or letters
Geneva College Bearer Falls, Pennsylvania 1.5010
Use of Punctuation Marks and Spaces Order of Constituents How are ofher Chorocfers Used in Nomenclafure?
Besides letters, numbers, primes, and enclosing marks, chemical nomenclature utilizes several other characters. How are these properly used? Perhaps the most common of these characters is the hyphen. It is used to set off various locants and descriptions from the rest of the name. a-quartz p-phenylenediamine 1,2-dichloroethane 1.3-nrananedivl-2-vlidene
A colon is used to separate the locants indicating the positions of attachment in hydrocarbon ring assemblies. 3"
1''
A colon is also used in naming dianhydrides.
For bridging groups, the symbol and the bridging group are separated from the rest of the name by hyphens. hexaamminedi-phydroxo-~-nitrito-0,N-dicobalt(3+) ion
A hyphen is used between numerical or other locants with q to indicatc the inclusive atoms involved in linkage to a metal.
A hyphen is used to separate the tx~osets of locants in the names of some fused ring systems.
A colon is also used in the names of ccrtain fused ring compounds.
(The naming of certain complex boron hydrides is based on this same pattern.) Among inorganic compounds and organic molecular compounds the colon is usedinindicating the proportions of the constituents. BiCla.3PCL NH8.CsH..Ni(CN)2
A common fault is thc overuse of hyphens. As a carry-over from common practices in writing, the hyphen is often used when two like vowels are together:
bismuth trichloride-phosphorus trichloride (1:3) ammonis-benzene-nickel(I1) cyanide (1:l:l)
However, the diagonal or solidus is now rccommended for this purpose. Volume 49, Number 5, May 1972
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333
duminum chloride/ethyl alcohol (1/4)
AICb .4CzHsOH
A semicolon is used to separate two sets of locants in a doubly fused name.
GeHl germane ICo(N0ddNHs)~I triamminetrinitritocobs1t Benzo[1",2":3,4; 4", 5":3,,4']dicyclobnta[l,2-a:l',2-a'+ diindene
A period is used to separate the numbers representing the length of the bridges in bridged hydrocarbons and heterocycles. HICCH-CH-CH* H
1
H 1
H I
H I
common only among hydrides and neutral coordination entities.
tricyclo[5.3.1.1~~~]dodecane
The use of periods in the naming of spiro hydrocarbons is similar.
The nomenclature for organic compounds calls for both single and multiple-word names. Among many practicing chemists, there is some uncertainty as to when to use single- and when to use multiple-word names. Maqy names for organic compounds are constructed on the basis of substitution on a fundamental compound: e.g., in C ~ H S C Eethyl H ~ may be considered as an ethyl group substituted for a hydrogen in the fundamental compound benzene. In such cases tho names are single words. Although C2H50H may be regarded as a substitution product of water, HOH, the name used is not ethylwater but ethyl alcohol. Alcohol is not the name of a fundamental compound but of a general class of compounds. Names such as ethyl alcohol are known as radicofnnctional names. Other general class names are ketone, ether sulfide, sulfoxide, acid anhydride, glycoside, and oxides. CHI)^
The Chemical Society (London) Handbook recommends commas for the above uses. The center point is often confused with the period. The center point is used to separate the components of molecular addition compounds or the component oxides of a mineral.
The center point is also used in place of a dash to represent a bond.
(CaH8)nS CHzCOCIHs CHaCO-O-OCH
methyl sulfide or dimethyl sulfide ethyl sulfide or diethyl sulfide ethyl methyl ketone acetic formic anhydride beneothiophene 1,l-dioxide
Acids, salts, and esters are two-word names paralleling inorganic terminology. Amine is regarded as a contraction for ammonia and hence is used as the root to which the name of a substituent is directly attached as prefix. Other comparable root substances are arsine, hydrazine, and toluidine. CH8NHp methylamine CeH5AsHn phenyhwsine 2,4(O*N)2CsHsNHNH* 2,4dinitrophenylhydraaine
Spaces in Names
Among inorganic compounds, spaces in names are very common. Most binary and pseudobinary compounds, whether ionic or covalent in character, have two-word names. NaC, C1PBra K+, OH-
sodium chloride phosphorus tribromide potassium hydroxide
This is also the case with ternary, etc., acids, bases, and salts. H%SO, sulfuric acid NR,+, OHtetraalkylammoniumhydroxide [NH41a[TeMosOu1,7Hs0 hexaammonium hexrtmolybdotellwate heptahydrrtte [Co(NH&lH, 3Clhexaamminecobalt(3+) chloride
Spaces separate the words in the names for acid, basic, and double salts.
(The Commission on Inorganic Nomenclature does not sanction the separation of hydrogen and carbonate on the basis of wanting to indicate by the name the presence of the ion, HC0,-.) In general, single word names for compounds are 334
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Journal of Chemical Education
What does one do when a substance with a two-word name becomes a ligand in a coprdination compound? The two-word name is retained and the complete name of the ligand placed between enclosing marks. [Ni(C4H,N~01)~1 bis(2,3-butanedione dioximato)nickel W h a t are the Orders for listing Related Constituents?
There are several places in inorganic nomenclature where i t is desirable to have a definite order in the listing of related constituents in compounds. These include acid salts, double salts, ligands in coordination compounds, suhstituents on chains and rings, and replacing atoms in replacement nomenclature. Although salts are named by listing the cation or electropositive constituent first there are a number of binary compounds which are not at all salt-like. Hence, some rule to specify which element to list first is desirable. In the 1957 IUPAC Inorganic Rules, there were several separate orders for listing related groups. There was an order for first listing in binary compounds between non-metals and another for intermetallic compounds. There was an order for listing cations in double salts and another for anions. For coordination compounds there was a rather complicated order for listing anionic ligands and another for neutral ligands. While these separate orders were interrelated, it was
not possible to reduce them to a single or a pair of orders. Hence, it is not surprising that authors either became confused with the lists, forgot some of the details, or gave up in disgust. The 1971 Rules have greatly simplified the orders for listing. A wntinuous line has been drawn through the long form of the periodic table as shown in the figure. (This sequence has many uses in the nomen-
NanC1F(S04)2 CajF(POdr BiOCl
hexasodium chloride fluoride bissulfate pentaealeium fluoride trisphosphate bismuth chloride oxide
Among coordination compounds all ligands regardless of charge are listed alphabetically. A wide variety of groups act as ligands. However, the number of different kinds of ligands in any one compound usually causes no confusion as to the formal charge on each ligand.
In organic nomenclature, the alphabetical order is used for the listing of groups in substitution products of hydrocarbons, etc. clature of coordination compounds, of organometallic compounds and elsewhere.) For binary compounds between nonmetals, that constituent is placed last which comes earliest in the sequence (most electronegative). XeFn SzC12,OF*
Exceptions are permitted in the cases of oxygen (inserted between F and Cl): hence CLO, and hydrogen (inserted between Te and N). In intermetallic compounds the constituents are placed in alphabetical order of their symbols unless one wishes to emphasize ionic character. AgZn, BeCu, CuZn, hut NasBis
-
~
The order of elements in replacement nomenclature is by descending group number in the periodic table and increasing atomic number-an order agreeing with the line through the periodic table above
CH,'
CH,
1 ' 0 1
CH, 31
For acid salts the word hydrogen is placed immediately in front of the name of the anion. NaHSOa LiHaP04
sodium hydrogen sulfite lithium dihydrogeu phosphate
In double salts both the cations and also the anions as separate groups are listed in alphabetical order.
E,"c"b,
magnesium potassium fluoride potassium sodium carhonste NaNH,HPO, .4HaO ammonium sodium hydrogen phosphate tetrahydrate
CHz 1 2 3 4 5 6 7 8 191011 HWCHrCHrS-CHrCHrNH-CHrCH1-As-CH2-CHrNH1 9-methyl-3-thia-6aza-9-arsa-1, 11-undecsnedismine
and for the names of clusteis. BtoCPHn l-phosph~2-carhsicloso-dodeeaborane(ll)
Volume 49, Number
5, May 1972
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335
