Volume 4, No. 2 
April 2000

Dr. Claff



An Amazing Tribe
by Gabe Bokor
Index 1997-2000
  Translator Profiles
Reflections on a Translator’s Life
by Susanna Greiss
  The Profession
The Bottom Line
by Fire Ant & Worker Bee
Sorry Guys, You Can't Win
by Danilo Nogueira
Un Secreto Bien Guardado
by Daniela Camozzi y Daniela Rodrigues Gesualdi
  Translators and Computers
XML and the Translator
by Alan K. Melby, Ph.D.
  Genealogical Translation
Translating for the German Genealogy Market
by Ann C. Sherwin
Lexicographical considerations in creating an online bilingual lexicon for students from a Chinese background
by Christopher Greaves and Han Yang, Ph.D.
  Science & Technology
A Translator’s Guide to Organic Chemical Nomenclature XIX
by Chester E. Claff, Jr., Ph.D.
  Caught in the Web
Web Surfing for Fun and Profit
by Cathy Flick, Ph.D.
Translators’ On-Line Resources
by Gabe Bokor
  Translators’ Tools
More Translation Memory Tools
by Suzanne AssÚnat-Falcone
Translators’ Emporium
Translators’ Events
Call for Papers and Editorial Policies
Translation Journal


A Translator’s Guide to Organic Chemical Nomenclature

Part XIX

by Chester E. Claff, Jr., Ph. D.

XI. Aromatic compounds (continued)

Monosubstituted benzenes

Some examples of monosubstituted benzenes are listed below with their widely-used names. The name listed first is the most commonly used name.

C6H5CH3  (PhCH3, PhMe, jCH3)  Toluene
C6H5CH2OH  (PhCH2OH etc.)   Benzyl alcohol
C6H5CH2BrBenzyl bromide
C6H5CHBr2Benzylidene bromide
C6H5OHPhenol; carbolic acid
C6H5CO2HBenzoic acid
C6H5CH(CH3)2Cumene; isopropylbenzene
C6H5CH=CH2Styrene; vinylbenzene
C6H5CH=CHCO2HCinnamic acid

Disubstituted benzenes

The 6-membered ring structure of benzene allows for the existence of three positional isomers of disubstituted benzenes. Locants are specified by either of two systems: The numbered system (1,2-, 1,3-, or 1,4-disubstituted) has its counterpart in ortho-, meta-, or para-disubstituted (abbreviated o-, m-, or p-disubstituted), respectively. Because the benzene ring is planar, no stereoisomers can exist.

The three dimethylbenzenes, for example, are:


Many other disubstituted benzenes have commonly used trivial names. Among them are:

o-, m-, p-CH3-C6H4-CH(CH3)2o-, m-, p-Cymene
o-, m-, p-CH3-C6H4-OHo-, m-, p-Cresol
o-, m-, p-CH3-C6H4-CO2Ho-, m-, p-Toluic acid
o-HO-C6H4-CO2HSalicylic acid
o-CH3CO2-C6H4-CO2HAspirin; acetylsalicylic acid
o-, m-, p-C6H5-C6H4-C6H5o-, m-, p-Terphenyl
o-HO2C-C6H4-CO2HPhthalic acid
m-HO2C-C6H4-CO2HIsophthalic acid
p-HO2C-C6H4-CO2HTerephthalic acid

Trisubstituted benzenes
1,2,4-C6H3(CO2H)3Trimellitic acid
1,3,5-C6H3(CO2H)3Trimesic acid
2-Hydroxy-3-methylbenzoic acid   o-Cresotic acid
2-Hydroxy-4-methylbenzoic acid   m-Cresotic acid
2-Hydroxy-5-methylbenzoic acidp-Cresotic acid

The number of known trisubstituted benzenes can readily be imagined from the short list above. Many have trivial names, but many do not. When in doubt of the translation of a trivial name, The Merck Index, Merck & Co., Inc., Rahway, NJ, USA, is an invaluable and relatively inexpensive first reference. The next stop of the author when still in doubt is an Internet search. Naturally tetra-, penta-, and hexasubstituted benzenes abound.

Although our coverage of aromatic compounds has only scratched the surface of this topic, it's time to move on to broaden our base of categories.

XII. Heterocyclic compounds

Three major methods exist for naming heterocyclic compounds:

1) The Hantzsch-Widman Suffix method, first proposed in 1887-8 and since modified;

2) The replacement method, also widely used;

3) Trivial names.

The Hantzsch-Widman system is clarified by a careful study of the tables below. In the replacement system, the rings are first named as if all ring members were carbon atoms. The hetero atoms are identified by prefixes from the table on the next page. The trivial system, of course, often defies explanation.

Hantzsch-Widman Suffixes

The tables below are reproduced from "Nomenclature of Organic Compounds," Advances in Chemistry Series #126, American Chemical Society, Washington, D.C., 1974.

Hantzsch-Widman Suffixes

 Rings Containing NitrogenRings Without Nitrogen
Ring MembersUnsaturatedaSaturatedUnsaturatedaSaturated

a Having the maximum number of conjugated double bonds.
b Immediately preceding -ine or -in the special prefix names phosphor, arsen, and antimon are used rather than phospha, arsa, and stiba.
c Expressed by prefixing perhydro to the names of the corresponding unsaturated ring.
d For Si, Ge, Sn, and Pb, perhydro is prefixed to the name of the corresponding unsaturated ring.

Special Hantzsch-Widman Suffixes

Ring MembersRings Containing NitrogenRings Without Nitrogen

These suffixes indicate partial saturation.

Every suffix requires a prefix; the most common hetero atoms (i.e. non-carbon atoms) to be identified as part of a heterocyclic ring system are:

Phosphorus   phospha-

The final a- is often elided preceding a leading vowel in the suffix. The system can best be understood by examples. Let's first consider a very common hetero atom, nitrogen, and the most common ring size, six members. The name shown in bold typeface is the one most commonly encountered in the literature.

Hantzsch-Widman name:Azine
Replacement name: Azabenzene
Trivial name: Pyridine
Hantzsch-Widman name:1,4-Diazine
Replacement name: 1,4-Diazabenzene
Trivial name: Pyrazine
Hantzsch-Widman name: 1,3-Diazine
Replacement name: 1.3-Diazabenzene
Trivial name: Pyrimidine
Hantzsch-Widman name:   1,2-Diazine
Replacement name: 1,2-Diazabenzene
Trivial name: Pyridazine
Hantzsch-Widman: 2,4,6-Triamino-1,3,5-triazine
Replacement: 2,4,6-Triamino-1,3,5-triazabenzene
Trivial: Melamine
Hantzsch-Widman: 2,4,6-Trihydroxy-1,3,5-triazine
Replacement: 2,4,6-Trihydroxy-1,3,5-triazabenzene
Trivial: Cyanuric acid
Each of these compounds is an aromatic heterocyclic compound and contains the maximum number of conjugated double bonds (3), and its Hantzsch-Widman name is therefore derived from the first Unsaturated column of Table 6.2 above. If one or more of the double bonds are saturated by addition of hydrogen, the prefix hydro with appropriate locants and multipliers is added:
Hantzsch-Widman: 1,2-Dihydroazine
Replacement: 1-Azacyclohexa-3,5-diene
Trivial: 1,2-Dihydropyridine
Hantzsch-Widman: 1,2,3,6-Tetrahydro-1,3-diazine
Replacement: 1,3-Diazacyclohex-4-ene
Trivial: 1,2,3,6-Tetrahydropyrimidine   
Hantzsch-Widman: Perhydro-1,4-diazine
Replacement: 1,4-Diazacyclohexane
Trivial: Perhydropyrazine


Part XX will continue the discussion of nitrogen heterocycles and will add the excitement of oxygen in the ring!