National Chemistry Week - Experiments - CELLULOSE MOLECULES: LEFT OR RIGHT-HANDED?

Most objects that occur naturally are not identical with their mirror images. This characteristic is called "chirality" or "handedness." The two forms are often designated right- handed and left-handed. Your hands are "chiral" and so are many molecules.

Cellulose, the chief constituent of cell walls of plants, is the most abundant polymer in nature. Its structure makes an essential contribution to the properties of pulp, paper and many other materials based on wood. Cellulose is a chiral molecule and this characteristic can lead to some unexpected properties in some of the materials that contain it.

To observe the chirality of this polymer using newspaper (which is made from cellulose) perform the following exercise.

1. Cut strips of newspaper horizontally so that they are 1 cm wide and 25 cm long. Mark the strips "horizontal".

2. Cut strips of newspaper vertically, so that they are 1 cm wide and 25 cm long. Mark the strips "vertical".

3. Wet each strip of paper and hang it to dry with a paper clip at the bottom.

Is cellulose a left-handed or right-handed helix? Consider that the cellulose fibres are probably oriented in certain directions due to the newsprint-making process.