nomenclature C~H~.NHXN~(CN)~
ammania/benzene/nickel(II) cya-
nide (11111~) The previous practice was to use the colon in place of the solidus to denote the ratio of numbers. Example
BFa2H20 baron trifluoride-water (1:2) An alternative method for indicating the ratio of constituents in an addition compound is by the use of numerical prefixes ( 4 ) . Example UniverGty of South Florido Tamp.
Chemical Abstrocl%Service
KURT LOENING ROY M. ADAMS
33620
Columbu%,Ohio 43210 Genera College
Bearer
Folls, Pennsylvonio
1.501 0
~(CH&S.BIOCISH~ bis(dimethy1sulfide)-hexachlorodecaborane (8) This method is particularly useful to avoid any posiible conl'uaion with other n~tmhrrsenclosed in parentheses-in this mse the numher of hydrogen atmns in t h r parent borsne. There is no general agreement on the order of citation of the ...... of an addition nmoound. The Red Rook states: nmsriruenti "Boron compounds and water are always cited last in that order. Other molecules are cited in order of increasing number; any which occur in equal numbers are cited in aldhabetical order." However. horon chemists have always preferred to list is included in the "donor" molecule first (3)and such a those for inorganic horon compounds ( 4 ) . ~
Addition Compounds Deeply ingrained in the fabric of chemistry since the time of Lavoisier is the concept of two unlike molecules reacting to form a new species. Among such compounds are hydrates: CaS042HzO; ammoniates: NaC1.2NH3; and molecular addition compounds: EtzO.BF3. The structure of such compounds is well known and they can he given names to indicate these structures. [Ca(H20)21SO1 [Na(NHhICI RFaOEt2
diaquacalcium sulfate diamminesodium chloride (diethyl ether)trifluorohoron
The need for general terms to include all compounds with "water of crystallization" and all compounds with "ammonia of crystallization" has led to the wide-spread use of "hydrates" and "ammoniates" for this ourpose. However, the extension of this practice has certain pkfails since the ending -ate is now the accepted ending for anions generally. Hence, alcoholates are the salts of alcohols rather than compounds with "alcohol of crystallization." Quite aside from these donor-acceptor complexes, there is a wide variety of lattice or clathrate compounds. In these, spatial rather than chemical considerations dominate. While the stoichiometry for each of these is definite, the ratios are seldom simple. Thus, there is need for a general pattern of nomenclature to deal with these addition compounds, specifically, and all addition compounds, generally. The names of addition compounds are formed by connecting the names of individual compounds by spaced hyhens (IUPAC) ( I ) or by the solidus or slash (ACS) (2) and indicating the number of molecules after the name by Arabic numerals separated by the solidus. Examples
3CdSOeXHsO AI2(SO&KzSOc24HzO, BiCldPCIs XKr.46H20
cadmium sulfate-water(318) cadmium sulfatelwater (318) aluminum sulfate-potassium sulfate-water (111124) bismuth trichloridelphosphorus pentachloride (113) krypton-water (8146)
354, / Journal of Chemical Education
Examples
NH3.B3H7 ~(CH~)~N.BI&IN
ammonia-triborane(7) bis(trimethylan?ine)-dodecahorane(l0)
Boron chemists have also introduced another practice. If there are possible alternatives in the manner of attachment to the horon or if it is desirable to emphasize the of the lieand " manner of attachment, the dash (or solidus) between the molecular constituents is reolaced hv oarentheses enclosing the symbols of the two elements forming the bond separated by a dash. Examples
OC-BHB CH3ONH2.BHj
carbon monoxide (C-B)borane O-methylhydroxylamine(N-Rlborane
Literature Cited .. 11973). 13) Dawdmn, N..and Brown, H.C . d Amm Chsm. Sor.. 64.317 119421. (4) .'NomendatweofInorganic BamnCompaunds."R~reAppppl. Chrm.. 30 (3d!, c f l n o r g Chem., 7 1101.1952 1196Ri.
69911972):
Historical Development of Chemical Nomenclature Historians of chemistry have devoted comparatively little attention to nomenclature. The one serious study (1) does not extend beyond the Geneva Conference (1892).Consequently, some recent articles bv P. E. Verkade entitled "Historical - - - - ~ ~ Studies on the ~ o m e n c k u r of e Organic Chemistry" are most welcome. Professor Verkade was a member of the Commission on the Nomenclature of Organic Chemistry for half a century and its chairman during most of that time. Thus he writes from first-hand knowledge. The titles of the individual articles are ~
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