I’ve recently written a proposal for a 16-19 Chemistry syllabus for a group of Egyptian schools to fit the brief that it should meet ‘International Standards’ as well as fit the Egyptian curriculum. This has meant looking in detail at other internationally recognised programmes such as the International A Level, the Pre-U Cambridge Examination, Advanced Placement (AP) and the European Baccalaureate (EB) as well as the International Baccalaureate. It has been an interesting exercise and one in which the IB comes out of rather well. Even so, we can learn from other programmes and consider what they include and what we leave out and vice versa.

The IB is quite distinct in having so many options. This has many advantages and indeed I was one of the teachers pressing for this when the syllabus was overhauled in 1996 so that the good points from Applied Chemistry could be incorporated when it was subsumed into Chemistry. There are some disadvantages though. It worries me that a Chemistry student can gain the IB Diploma without knowing anything about the principles and uses of spectroscopy and personally I think it was a mistake to remove the basics of this from the core during the last review in 2007. One other noticeable fact is that some of the other programmes place more emphasis on Objective 3 and less emphasis on recall than the IB. In the IB Objective 3 type questions are  worth 28% of the final mark whereas for A level and the Cambridge Pre-U they  are worth 30% and 40% respectively.

There are many topics that we used to include such as colligative properties that are still retained in some of the other programmes (e.g. AP) and we have topics, such as Combinatorial Chemistry, which as far as I am aware do not appear in any other 16-19 year old Chemistry syllabus. But what are the topics that other programmes cover which we have never included?

The Cambridge Pre-U Chemistry syllabus has some interesting new topics.  These include van Arkel diagrams, C-13 NMR and anti-bonding orbitals. Another topic that occurs on some of the other programmes is the concept of ‘atom economy’ which fits in with the idea of ‘Green Chemistry’.

Van Arkel diagrams are used to help explain the bonding in all types of binary compounds. By plotting their position on a single graph using electronegativity values a van Arkel diagram aims to unify all chemical bonding types whether they are ionic, covalent, metallic or semi-metallic. It is a step-up from the rule of thumb (which does not work very well) that a compound is ionic if the difference in the electronegativity values of the two constituents is more than 1.8. However I personally do not find them much more convincing than just interpreting the electronegativity values within the context of the Periodic Table.

Carbon-13 NMR. I wonder if this is included as it is simpler to deal with than ¹H NMR. The big advantage of C-13 over ¹H NMR is that the chemical shifts are predictable and the spectra are routinely decoupled. The Pre-U claim that as a result questions can be considered that involve more complex and interesting molecules. However the real strength of ¹H NMR is the splitting patterns caused by neighbouring protons. I feel that once students understand how to interpret splitting patterns and the integration trace then the chemical shift becomes less necessary as a tool to elucidate structures. From an intellectual point of view I favour ¹H NMR over C-13 but of course the best outcome would be to have both on the syllabus!

Anti-bonding orbitals. I always feel uncomfortable that the IB includes molecular orbitals and hybridisation but does not include anti-bonding orbitals when looking at the combination of atomic orbitals to form molecular orbitals. For this reason I have included a brief mention of them in my IB Chemistry Course Companion. The Pre-U includes them for their importance in spectroscopy. How else can one explain the transitions that occur when considering whether an organic molecule will absorb in the UV or visible region? Currently in the IB we just mention degree of conjugation (or delocalisation) but an understanding of electronic transitions to anti-bonding orbitals would be helpful here.

Atom economy. This term was coined by Barry Trost of Stanford University US (for which he received the Presidential Green Chemistry Challenge Award in 1998).  

     Atom economy = Mass of atoms in desired product  x100
                                   Mass of atoms in reactants

This is different to, and more useful than, the percentage yield. The percentage yield gives some useful information but does not show how efficiently the reactants have been used in industrial processes or how effectively the amount of waste products is being reduced. The real strength of using the concept of atom economy is in comparing different routes or pathways to synthesise the same product.

When the IB Chemistry programme next comes up for review it would be worth the reviewers considering what changes would bring the IB more up-to-date. There is not room to include everything in the programme so by necessity a judgement has to be made and some valid topics omitted. However, some of these topics omitted from the programme can still be included in the examination as they provide fertile material for the Data Response questions in Section A of Paper 2.  Here much of the necessary background information can be provided to the students in the questions. You can also use these omitted topics in your teaching to stretch your students and challenge and prepare them to apply their knowledge to solve problems in unfamiliar areas.