Glutaraldeyhye is the common name for pentanedial.
Glyoxal is the common name for ethanedial.
The suffix 'al' means aldehyde, a carbon atom with a double bond to an
oxygen atom AND to a hydrogen atom. Since a carbon atom can only be
involved in four bonds, and the double bond and single bond add to three,
the carbon (and thus the aldehyde group) MUST be at the end of a molecule.
'dial' means two aldehyde groups, necessarily one group at each end of the
-C-C- chain.
The prefix 'eth-' means 2. 'Pent' of course mean 5. Thus 2 carbon atoms
in the chain vs 5 carbon atoms in the chain. So, pentanedial is like
ethanedial with 3 carbon atoms (and associated bonds to H atoms) added in
the middle of the chain, between the 2 carbons.
If you are looking at this message (or can change the display of the
message) in a monospaced (non-proportionaly spaced) font, the structures
are:
O O O H H H O
# # # | | | #
H-C-C-H H-C-C-C-C-C-H
| | |
H H H
where I have used # to mean a double bond.
Then to make life interesting, there is glyceraldehyde, which is
2,3-dihydroxypropanal. 'Pro' means 3. 'hydroxy' means -O-H. To test your
knowledge, you might want to draw that stucture. The route of this word is
more obvious than for the original two, because glycerine (also called
glycerol, where '-ol' means an alcohol, thus C-O-H )is the common name for
1,2,3-propanetriol. For extra credit, compare the structures of
glyceraldehyde and glycerol.
I hope out of all this that you see the problems with 'common names' and
thus the more useful systematic names.
John Bordley