Wayde Allen (wallen@boulder.nist.gov)
Thu, 21 Jan 1999 11:46:09 -0700 (MST)
On Mon, 18 Jan 1999 FotoDave@aol.com wrote:
> Also, does anyone know what the numbers behind the chemical could possibly
> mean? I am not sure if they are simply their internal part number or if they
> something chemically.
In the IUPAC system of nomenclature the numbers indicate bonding positions
for the various functional groups. From my old textbook, Fessenden R.J.
and Fessenden J.S., Organic Chemistry Second Edition, Willard Grant Press,
1982, page 105:
The IUPAC system of nomenclature is based on the names of the
continuous-chain alkanes as parents. If a hydrocarbon chain forms a
ring, the prefix cyclo- is added to the alkane name. Branches and
functional groups are indicated in a name by prefixes or suffixes.
The longest continuous chain containing the functional group (if any)
is the parent. The chain is numbered from the end nearer to the
branches or functional groups. (The functional group of highest
priority, as listed in table 3.5 [I'm not including the table],
receives the lowest number.) Positions of substitution on the chain are
then specified by these numbers.
Cl
|
1,4-dicloro-4-methyl-2-pentene: CH3CCH=CHCH2Cl
|
CH3
[I can't label this very well using ASCII graphics so you'll have to
count the carbon atoms yourself. The first C on the left is number 5, the
next one is 4, etc.]
The (-) or (+) symbols indicate which of the enantiomers of a chiral
molecule you have. A chiral molecule is one with a plane of symmetry like
your two hands. They are mirror images of each other, but can not be
directly superimposed. The + or - indicates whether you have the left or
right handed version. More correctly, the symbols indicate the direction
that a mixture of this enantiomer would rotate the plane of polarization
of light passing through the solution.
Hope this helps. It has been about 15 years since I've used this stuff,
so I'm pretty rusty.
- Wayde
(wallen@boulder.nist.gov)
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