Avid subscribers to this website will have looked at the pages on using the IB Data Booklet creatively to give them ideas as to how they can enhance their teaching of some of the concepts contained in the assessment statements. Students like to relate chemistry to ‘real life’ and by stimulating their interest they can understand fundamental concepts more easily. It also prepares them for Objective 3 type questions in the final examination which requires them to think rather than just regurgitate assessments statements and teacher’s notes from the guide.

News items can also generate great material for teaching ideas and help you connect with your students while also increasing their understanding. Recently the BBC put out an article about how the use of ketamine as a recreational drug has increased over the past decade. This was forcibly brought home by a report today which claimed that Amy Winehouse bought ketamine (along with cocaine and ecstasy) in the hours leading up to her untimely death. So what is ketamine?

A quick look on the Internet will give both its formula and some background information. It was originally developed as an anaesthetic and was used by surgeons on the battlefields of the Vietnam war in the 1960s. Mostly now it is used in animal surgery (particularly with horses) but since the 1970 it has also been used as a recreational drug by clubbers.

Although pure ketamine is a liquid it is available in powdered form as its hydrochloride salt (see image on left) and so is sometimes confused with cocaine and crystal methamphetamine. It is said that its hallucinogenic effects can range from rapture to paranoia to boredom.

Its IUPAC chemical name is 2-(2-chlorophenyl)-2-(methylamino)cyclohexanone. So how can it be used in teaching?

All the groups it contains are listed in the HL programme (assessment statements10.1 and 20.1) so we could start by getting students to build up the molecule from its name.

1. Get them first to draw cyclohexanone and then identify the second carbon atom.

2. Place a methylamino group on the second carbon atom (to form a secondary amine).

3. Then place a 2-chlorophenyl group also on the second carbon atom to give the required structure.

ketamine 

You can then get them to build a model (or show them a '3-D' representation) of the structure. 

The molecule possesses several interesting features which illustrate important points on the IB Chemistry syllabus.
 

1. Polarity. Would your students expect the molecule to be soluble in water or fats? In fact it is slightly soluble in water due to the possibility of the hydrogen atom on the secondary amine forming some hydrogen bonding with water molecules – however it is essentially a not very polar molecule and is much more soluble in non-polar solvents.
 

2. Given that it is not very soluble in water how can its solubility be increased? It is a secondary amine which means that it is basic. Assessment statement G.8.3 covers this. By converting the molecule into its hydrochloride salt (the white powder used by clubbers) it can be made much more polar. This is similar to the examples on the syllabus of morphine and fluoxetine and are also covered under assessment statement D.9.4 - Discuss how the polarity of a molecule can be modified to increase its aqueous solubility and how this facilitates its distribution around the body.

3. It contains a ketone group. You could ask your students to give the equation for its reaction with 2,4-dinitrophenylhydrazine (G.4.1) or ask them to devise a two-step synthesis to turn ketamine into a carboxylic acid with the formula: 

This covers both G.2.2 (nucleophilic reaction with hydrogen cyanide) and G.2.3 (hydrolysis of cyanohydrins) and G 7.1 (reaction pathways).

4. If you are teaching option A you could ask them what characteristic peak would be seen in the IR spectrum of ketamine (A.3.2). The obvious answer being a sharp single peak in the region of 1700 – 1750 cm^-1 due to the C=O bond absorption .

5. Ketamine contains a carbon atom bonded directly to a halogen atom. During a review (US) or revision (UK) of nucleophilic substitution reactions you could ask students how they would expect ketamine to react with warm dilute aqueous sodium hydroxide solution. Because the chlorine atom is bonded directly to a phenyl carbon atom this neatly covers assessment statement G.5.2  - Describe and explain the relative rates of hydrolysis of benzene compounds halogenated in the ring and in the side chain.

6. Ketamine is also interesting as it is a chiral molecule so an obvious question would be to get the students to identify the asymmetric carbon atom within the molecule. 

One way to represent the two different enantiomers of ketamine

This covers assessment statement 20.6.5 and you could go on to ask about how the properties of the two enantiomers might differ (D.8.2 ) and how they could be distinguished (20.6.6).

A lot of good IB chemistry contained in one small molecule!