FoundationalConceptsNeuroscience

H2C mY CHsz 35 CH 3

CCH

H3c~ 3 ~C~ H ‘ * CH 3

Branched octane

The chain of carbons may even fold back upon itself to form a
closed ring. Here is an example of that, the cyclohexane molecule.
Note that in all cases each carbon atom still forms four covalent chem-
ical bonds and each hydrogen atom forms one covalent bond.

H ‘i H

fy

HH

Cyclohexane

There is another cyclic arrangement of six carbons that occurs
commonly in nature. The benzene molecule contains six carbons ina
ring structure together with six hydrogens (rather than twelve hydro-
gens, as in cyclohexane). The existence of such a combination of six
carbons and six hydrogens was puzzling until Friedrich Kekulé (1829-
1896) suggested a novel structure in 1865 for benzene.