Functional groups

Background

The homologous series covered in the core under 10.1 are the alkanes and alkenes and the functional groups are: alcohols, aldehydes, ketones, carboxylic acids and halogenoalkanes. Students should be able to name compounds containing one of these groups for up to six (non cyclic) carbon atoms. In addition students should be able to identify the amino group, the benzene ring and esters. They should also be able to distinguish between primary, secondary and tertiary alcohols. For HL (20.1) students they are also expected to cover amines, amides and nitriles.


When teaching functional groups and the IUPAC system of naming teachers often simply follow the syllabus and limit themselves to compounds containing up to six carbon atoms. The teaching can get rather repetitive and many of the compounds are not compounds that students can easily relate to. Consequently students often initially tend to muddle the groups up. The structures given in Tables 20, 21 and 22 in the data booklet can be really useful to reinforce identification of functional groups. Some examples to ask students are:


Example 1 What is the difference between male and female students?

testosterone progesterone

Both testosterone and progesterone contain a ketone group (hence the ending in –one) but progesterone contains a second ketone group (perhaps it should be called progesterdione?) and testosterone contains an alcohol group (perhaps it should be called testosteronol?).

(Place your cursor over the proboscis money to find the answer)

Example 2 Alcohols

Find how many compounds there are in Tables 20, 21 and 22 that end in –ol. What functional group do they all have in common? Can you find any other compounds in the tables that also include this group?


Example 3 How does the structure of morphine differ from the structure of heroin?

morphine heroin

Example 4 Aspirin, penicillin and thyroxine

Aspirin, ibuprofen, penicillin and thyroxine all have one functional group in
common – what is it?

Example 5 Identify the functional groups present in cocaine

cocaine


Example 6 Use your imagination

There are many more ways of using these structures, e.g. is testosterone a primary, secondary or tertiary alcohol?