Adamantane 1: introduction

Adamantane is an alicyclic hydrocarbon with chemical formula C₁₀H₁₆. It is a colourless crystalline compound with a camphor-like odour that can be isolated from petroleum. Its name derives from the word "adamant" because of its high thermal stability.

In the structure to the left the carbon atoms are coloured grey and the hydrogen atoms white. Its structure can be seen to contain four six-membered rings. It is a more symmetrical molecule than it appears at first - it actually has tetrahedral symmetry. The four carbon atoms carrying only a single hydrogen in fact occupy equivalent positions, which correspond to the symmetry of corners in a tetrahedron. In this tetrahedral picture the four six-membered rings correspond to the four faces of the tetrahedron. By rotating the structure on the left you should be able to appreciate how the structure looks the same from the point of view of these CH carbons. When looking down one of these C-H bonds you can see how there is three-fold symmetry in the molecule. Combining the three-fold axes along the four C-H directions, it follows that the six CH₂ groups are equivalent. Therefore there are two types of carbon in adamanatane, so the carbon-13 NMR spectrum would give two signals. If you look carefully you should be able to work out there are also two environments of hydrogen in the molecule too: the CH hydrogens and the CH₂ hydrogens. The two hydrogens in a CH₂ group are equivalent by virtue of a mirror plane between them. Note how a similar carbon unit is visible in diamond, except that no hydrogen atoms are carried (see page 9 of diamond).

Go to page 2 to look at the unit cell within the bulk structure of adamantane.

Page 2