adamantane

A caged polycyclic saturated hydrocarbon. Beautiful in its sp3-hybridized tetrahedral bond angles, it can be seen as having three cyclohexane molecules sharing a common [ 1 ] carbon atom. This is not the fabled adamantium of Wolverine's claws.

To be more precise, it is four fused cyclohexanes in chair form. To see this it is necessary to see the structure - sadly this is beyond my ASCII art skillz. However, start with the base (a cyclohexane) and superimpose another cyclohexane around the symmetry axis that runs through the center of the ring:

           |
      _____|______
     /     |      \
    /      |       \
   /       |        \
  /       /|\        \
  \  B A  \_/ S  E   /   
   \                /
    \              /
     \____________/
           |
           |
           |
         AX|IS

Of course, this is a threefold symmetry axis - which accomodates the three other rings. These virtual rings 'share' every atom - all ten of them. As it is saturated - and because every other carbon is connected to three others - it has ten hydrogens.

C₁₀H₁₆