Many chemical compounds have several possible names. Peter Nelson, University of Hull, asks: 'Which ones should teachers use?'

Diazepam - chemical structure

Source: Wikipedia / Mysid

Chemical structure of diazepam, also known as Valium

The Association for Science Education (ASE) has addressed this question, and published a list of names for use at 16-19.1 These names are based on general rules for naming compounds approved by the International Union of Pure and Applied Chemistry (IUPAC).2 ASE names are used by examination boards, and have the approval of the Royal Society of Chemistry (RSC).

There is, however, a problem with these names in that many of them are different from those recommended by IUPAC (see Table).2,4 This is because IUPAC does not recommend a systematic name when another name is widely used. The editors of the guide to organic nomenclature explain this as follows:2b 

'In contrast to systematic names, there are traditional names, semisystematic or trivial, which are widely used for a core group of common compounds. Examples are 'acetic acid', 'benzene', 'cholesterol', 'styrene', 'formaldehyde', 'water', 'iron'. Many of these names are also part of general non-scientific language and are thus not confined to use within the science of chemistry. They are useful, and in many cases indispensable (consider the alternative systematic name for cholesterol, for example). Little is to be gained, and certainly much to be lost, by replacing such names'. 

By using ASE names, UK schools are out of line with the wider chemical and scientific community and the rest of the world. Academic and industrial chemists and other scientists use mainly IUPAC names. They also continue to use some traditional names not recommended by IUPAC (eg 'ethylene').

Proponents of the ASE names argue that these facilitate teaching. Using them, teachers create two major problems. The first is that, unless they also give the standard names, connections between school chemistry and everyday life are obscured. Pupils will meet compounds in school that are important in everyday life without realising it. They will also meet compounds in everyday life without realising that they have studied them at school. 

ASE and IUPAC names and compounds
Formula ASE IUPC
C2 H2 Ethyne Acetylene
HCHO Methanal Formaldehyde
CH3 COOH Ethanoic acid Acetic acid
CH2 =CHCl Chloroethene Vinyl chloride
C6 H5 CH3 Methylbenzene Toleune
NaClO Sodium chlorate(I) Sodium hypochlorite
NaClO2 Sodium chorate(III) Sodium chlorite
NaClO3 Sodium chlorate(V) Sodium chlorate
NaClO4 Sodium chlorate(VII) Sodium perchlorate

Examples of applications that the ASE names in the Box obscure are: 

  • PVC (polyvinyl chloride); 
  • PVA glue (polyvinyl acetate); 
  • oxyacetylene welding; 
  • use of acetic acid and acetates
  • (eg cortisone acetate) in medicine; 
  • cellulose acetate plastics; 
  • TNT (trinitrotoluene); 
  • sodium hypochlorite bleach; 
  • sodium chlorate weed-killer 
  • preserving biological specimens in formalin (aqueous formaldehyde). 

The RSC is currently concerned that the general public does not have a proper appreciation of the importance of chemistry. Using obscure names in schools does not help this. 

The second problem with schools using ASE names is that pupils either have to learn two sets of names to resolve the first problem, or, if they go on to study chemistry, medicine, or another science at university, have to learn a second set of names there. Given how many other things such students have to learn, to make them learn a new chemical nomenclature is an unnecessary extra burden. 

I would therefore urge the ASE and awarding bodies to think again about their nomenclature, and the RSC about its endorsement of this. Teachers can help by supporting this call. 

Related Links


Chemical Nomenclature and Structure Representation Division's provisional recommendations on nomenclature of organic chemistry