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Exeter Multimedia; Jones and
Bartlett: Sudbury, MA, 1996 (Macintosh), 1997 (Windows). $395.
This single CD-ROM presents 17 short
(2-3-minute) Quicktime, full-color movie animations of selected
organic reaction mechanisms, most of which are discussed at
the sophomore level. It is an ambitious and timely project
that seeks to move beyond the static, snapshot formalism of
the curved arrow to a seamless portrayal of electron flow in
three dimensions. Each movie, accompanied by text and
voice, is shown twice and includes at least one view or
rotation of an intermediate or transition state. The entire series
can be examined in an hour. The animations are interactive
as controlled by a QT slide bar. They vary in scope,
quality, and clarity. Quite effectively presented are alkene
bromination, hydrogenation and hydrohalogenation,
carbonyl enolization-alkylation, carbocation rearrangement, and
E2 elimination. A few other, more advanced, topics such as
the SN2', kinetic aldol, and Baeyer-Villiger reactions are
also included. Carbonyl addition and acyl substitution are
exemplified by imine formation and ester saponification.
Reactions of aromatics are not presented.
In this package, the reaction pathways are primarily
based on changes in overall geometry and bonding so the
emphasis is on highlighting those bonds being broken and those
being formed. Transition states are identified by the appearance
of a uniform color over all atoms, orbitals, and bonds.
Changes in hybridization and attendant stereochemistry
are nicely depicted but these animations are not meant to illustrate
or model the molecular orbital basis for reactivity. As an
example, the Diels-Alder reaction is shown proceeding with
endo specificity via a disrotatory motion of the diene and
subsequent rotation of the cycloadduct to a half chair
conformation but it is not presented as a HOMO-LUMO interaction.
In many of the mechanisms the reacting centers and
relevant interacting orbitals appear in vividly contrasting colors,
which aides visualization but may lend the unintended
impression that some reactants, intermediates, or products are in
antibonding states.
A useful adjunct is an indexing guide which links
the 17 animations to specific page references in 13 major
organic chemistry texts.
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