How to Build a Clean Box

arcarlini at arcarlini at
Mon Apr 16 16:31:09 CDT 2007

Andrew Burton wrote:
> When chemicals have 2 or more names, I often get confused. The only
> one I know by 2 names is Caustic (soda?), aka Sodium Hydroxide, which
> is used alot in the lab for various reagents.  
> Why have 2 or more names for the same thing (excluding American
> English/UK English spelling differences)? 

The IUPAC rules are designed to ensure that a conforming name
unambiguously describes the chemical structure. Ensuring that
names are unique is not a primary goal of the system. That
having been said, there are rules that describe the priority
assigned to most organic groups. I exepct that in the more
complicated cases there may well be some ambiguity, but
for something as simple as propan-2-ol I think both
1-methyl-2-ethanol and 2-hydroxypropane (while being
unambiguous) break the rules (the former fails to identify
the longest carbon chain, the latter uses a prefix that should
only be used in the prescence of a higher priority group).

In practice you'll see either propal-2-ol (the systematic name)
or isopropanol (the old name).


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