recommendation has found little favor among Englishspeaking chemists. Also the Commission consistently uses sodium hydrogencarbonate (NaHC03), lithium dihydrogenphosphate (LiHzPOd, etc. for the acid salts and hydrogensulfide (HS-), hydrogenphosphonate (HPHOa-), etc. for the anions. American chemists prefer to write hydrogeqin these names as a separate word: hydrogen carbonate (5-6). The IUPAC Commission on the Nomenclature of Oreanic Chemistry favors the separate words rather than the "f;sed" names (7). So also does the Chemical Societv (London) (8). noth he; difference of this same type is ox; acids. I~&AC recommendations comhine the two words whereas U S . practice is to keep them separated. Literature Cited 111 J. Amer C h ~ m Sor.. 82,5525 (19601. 121 Proc Am. Chem. S o r . 33 119261. 131 Smtt. J. D.. Chem. En& News., 37.48 (July 13,1959). 141 J. M d a l s . 325 1Mey 19581. 151 J. A m e i Chrm. Sol.. 82.5530.5536 119571. 161 Cr8ne.E. J . , J CHEM. EDUC..8.1336 119311. 171 "Nomenclature sf Owanic Chemistry, Sections A, B,and V, (3rd. Ed.1The Buttenvorth Gmup, London. 1971. Rule 462.1. 161 "Handbook ic,r Chemical Society Authors". 1961, pp. 26.34.
1) The descriptors cis (an this side) and trans (across) are still satisfactorywhere unambiguous. 2) The extension of cis and trans propxed hy Epstein and Raasini (2) greatly clarified the use of cis and tmm. 3) The "&-like" topographical nature of the letter E and the "trans-like" topographical nature of the letter Z are confusing. 4 ) Cis and trans are still retained for designating stereoisomers in monocyclic compounds, in fused ring systems with saturated bridgeheads, and in long chains in special cases (3).
The extension of cis and trans mentioned in 2) above was to specify whether the carbons of the fundamental chain adjacent to the double bond carbons are cis or trans, and to place the descriptor immediately before the number locating the double bond
However, the cisltrans system has limitations. Since suhstituents are cited in alphabetical order, separation of names of substitutents to be related stereochemically may result
Isomerism About A Double Bond: Use of CIS and TRANS A recent Note was devoted to the designation of isomerism about a double bond by the use of the descriptors Z (zusammen, together) and E (entgegen, opposed) ( I ) . James L. Lyle (California State College, Dominquez Hills, California 90747) has written urging that both the cisltrans and the ZIE systems for naming geometrical isomers he taught to undergraduate students and that the older cis-trans method has much to commend it. The specific points he makes are these:
This situation causes no problems for the E I Z system, in which the above structure would he labeled E. Literature Cited
Volume 53. Number 11, November 1976
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