Slides in this set
He who s t a rt e d i t
· August Kekule, 7th Sept 1829 13th July
· Studied at University of Giessen,
originally intended to study architecture
but changed his mind after attending a
chemistry lecture by von Liebig.
· Principle founder of the theory of
chemical structure, notably the structure
of benzene.…read more
Now for the part of any actual
importance... What WAS his
theory on benzene?
· Kekule suggested that the structure of
benzene was a 6 carbon ring with
alternating single and double bonds. The
technical name for this is a conjugated
double bond system.
· You could think of it as an alkene with 3
double bonds, but with a circular shape.…read more
Why does this rem
me of a certain
Years later, Kekule claimed that he came up with the idea of benzene's structure after
a daydream ...... of a snake chasing it's own tail!!!
< - - - - LOL…read more
k e s t o p l ay s w a p si e s . .
Although alkenes and benzene both contain double bonds, alkenes undergo
addition reactions (an element is added to the alkene, and thus breaking the
double bond), whilst benzene undergoes substitution reactions (literally just
swapping one atom for another, thus the double bonds are kept).
Some of the products of these substitution reactions are:
· Phenol (+ OH group)
· Toluene (+ CH3 group)
· Aniline (+ NH2 group)
· Biphenyl ( 2 benzene rings linked together)
Note : the old name for benzene was "phenyl", which is why, for example, a benzene ring with an alcohol group
attached is known as phenol and not as benzenol.…read more
So far, so simple, right? Errr......
That internal energy just
There is a slight issue when the topic of benzene's stability is mentioned. Based on
Kekule's structure, the stability of benzene would be a lot less than it actually is. This
can be proved by looking at the enthalpy changes of the hydrogenation of benzene.
Reminder, for those who are as forgetful as me: hydrogenation is the addition of hydrogenation to an unsaturated
hydrocarbon, thus breaking the carbon-carbon double bond and saturating the hydrocarbon.…read more