Re: TOJC; isomers

lietkeam@PLU.edu
Fri, 13 Sep 1996 16:24:17 -0800 (PST)

I believe there was some misinformation published in this journal
regarding the topic of constitutional isomers. Dennis Mitton was
definitely correct about the benefits of model sets in understanding
isomers. The correction I believe that needs to be made is in the
understanding of structural isomers. They are not a separate category
from constitutional isomers, but only a previous name for this type of
isomer. As our textbook states in a footnote on p. 6,

"an older term for isomers of this type was structural isomers. The
IUPAC now recommends that use of the term "structural" when applied to
isomers of this type be abandoned."

Constitutional isomers differ in their connectivity, an important concept
in this chapter. With rotating sigma bonds, you could attain different
shapes in the same molecule without ever changing its structure. This
does not mean it becomes an isomer, even though the shape is changed.

On Fri, 13 Sep 1996 mittondr@PLU.edu wrote:

> >
> Molecules with the same formula but different shapes or connections are
> isomers. Structural isomers differ in their shape - one branch might be
> left of center, one to the right. Constitutional isomers differ in the
> arrangement of the atoms within the molecule; the books uses ethyl
> alchohol and dimethyl ether as examples. Both have the formula C2OH6 but
> are connected in very different ways (see picture, page 5). Do you have a
> model set? I've been playing with one and it really helps to see what the
> book is talking about.
>
> Hope that helps....
>