11.3 - Other functional groups
Along with alkanes and alkenes, compounds containing one or more functional groups have been chosen to introduce students to interrelationships involving significant functional groups - important reaction types such as addition, substitution, oxidation, condensation, esterification and polymerization. This is expressed in the following scheme:
11.3.1: Draw and state the names of compounds containing up to five carbon atoms with one of the following functional groups: aldehyde, ketone, carboxylic acid, alcohol, amide, amine, ester and halogenoalkane. Functional groups in full and condensed forms are required, eg: Aldehyde: or RCHO. Carboxylic acid: or RCOOH
11.3.2: Explain that functional groups can exist as isomers. Examples include: ethanoic acid (CH3COOH) and methyl methanoate (HCOOCH3) propanal (CH3CH2CHO) and propanone (CH3COCH3)
11.3.3: Outline the existence of optical isomers.Restrict this to the fact that, if a carbon atom has four different substituents, the molecule exists in two enantiomeric forms that rotate the plane of polarized light in opposite directions. Students should be able to identify a chiral (asymmetric) centre.
11.3.4: Discuss the volatility, solubility in water and acidbase behaviour of the functional groups aldehyde, ketone, carboxylic acid, alcohol, amide, amine, ester and halogenoalkane. For example, use functional groups to explain the higher boiling point of methanol compared with methane. Cross reference with 4.3.
11.3.5: Outline the reaction of symmetrical alkenes with hydrogen, bromine, hydrogen halides and water. A double bond is relatively reactive, therefore molecules such as H2C=CH2 are important starting materials in organic synthesis.
11.3.6: Outline the uses of reactions of alkenes. Hydrogenation is used in the production of margarine, hydration of ethene is used in the manufacture of ethanol, and bromination can be used to distinguish between alkanes and alkenes.
11.3.7: Outline the polymerization of alkenes. Polyethene and polyvinyl chloride should be used as examples of addition polymers. Students should be able to draw the structures of the monomer and the repeating unit of the polymer.
11.3.8: Outline the condensation reaction of an alcohol with a carboxylic acid to form an ester, and state the uses of esters. Esters are used as flavouring agents, in plasticizers, as solvents and in perfumes.
11.3.9: Describe the partial and complete oxidation of ethanol. A suitable oxidizing agent is acidified potassium dichromate(VI). Both oxidation products (ethanal and ethanoic acid) can be obtained by altering the conditions, eg ethanal by distilling off the product as it is formed, and ethanoic acid by heating under reflux.
11.3.10: Deduce the condensation polymers formed by
amines and by carboxylic acids. Emphasize the need for two functional
groups on the monomers:
polyamides (nylons) eg hexanedioic acid and 1,6-diaminohexane polyesters - eg benzene-1,4-dicarboxylic acid and ethane-1,2-diol.
11.3.11: Outline the formation of peptides and proteins from 2-amino acids. All 2-amino acids (a-amino acids), except aminoethanoic acid (glycine), can show optical activity (see 11.3.3). Peptides are formed from amino acids, and two functional groups allow for the formation of macromolecules. Students should be familiar with simple primary structures (order of amino acids) for peptides containing up to three amino acids, eg: