L1 /
14
CH1012
NUMBERING IN
ORGANICS
Find the Highest Priority Functional Group (HPFG), numbering is based on the HPFG.
1) For
aldehydes, carboxylic acids
(+derivatives) the C=O is always C1.
(+derivatives) the C=O is always C1.
2) For
all other cases the HPFG is given the
lowest possible number in the chain.
lowest possible number in the chain.
3)
After this has been done the numbering
is intended to give the lowest numbering to
any remaining functional groups.
is intended to give the lowest numbering to
any remaining functional groups.
4)
After this any chain branches are given
the lowest numbering. Where there are
options (eg. 1,2-dimethyl or 1,3-dimethyl)
then the lowest sum is chosen.
the lowest numbering. Where there are
options (eg. 1,2-dimethyl or 1,3-dimethyl)
then the lowest sum is chosen.
5) An
HPFG attaches to a ring at C1.
