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The torsional angle driver system for
HyperChem/Excel is a package of several Excel spreadsheets and macro
programs to be used with HyperChem to obtain and plot
information, such as total energy, for the conformations that
result from a 360° rotation about a torsional angle system in
a molecule. The TorAD system also includes several HyperChem scripts to facilitate its use.
TorAD was developed for use in the undergraduate
organic chemistry laboratory. The results obtained with
TorAD could be obtained manually with HyperChem, but it
would take considerable time and would not be instructive to
the students. Use of the TorAD system allows students to
spend their time on the more important aspect of
conformation analysisinterpretation of results.
The Excel spreadsheet/macro programs in TorAD include:
· Tor_xl_a and tor_xl obtain and plot the total energy
at 5° torsional-angle intervals. The calculation method,
the torsional-angle restraint, and the structure to be used
at each angle can be set by the user. The advanced
version, tor_xl_a, which requires HyperChem 4.5 or later,
also allows torsional-angle structures to be saved for later
recall as individual structures or, using a HyperChem
script, in a movie format. It also provides a rapid scan of
the 360° rotation where only single-point calculations,
rather than geometry optimizations, are performed. The
tor_xl system will perform routine tasks in a manner
suitable for most instructional settings.
· Tor_Comp performs molecular mechanics
optimizations at 5° intervals and obtains and plots four energy
parameters (total, torsional, nonbonded, and bond
[bend plus stretch] energy) as a function of torsional
angle. The calculation method and the restraint can be specified.
· TorDipol produces a plot
of the total energy and the calculated dipole moment at
5° steps of the torsional angle.
The default calculation is the semi-empirical
AM1 method, but other methods can be used. The
calculation method and the restraint can be specified.
· Tor2_180 and Tor2_360 rotate two torsional angles
to provide a 3D plot of the resulting total energy
surface. Tor2_180 performs a 0 to 180° rotation, in 10° steps,
on each of the two torsional angle systems (tor1 and
tor2) selected. Tor2_360 will do a -180° to +180° (360°
total) rotation of the two torsional angles in 20° steps.
Both tor2_180 and tor2_360 provide an x,
y, z plot (x = angle 1,
y = angle 2, z = energy) and a topo plot
(x = angle 1, y = angle 2, z = topo lines and color coding). The
molecular mechanics method and the restraint can be specified.
Hardware and Software Requirement
Hardware and software requirements for Torsional
Angle Driver (TorAD) are shown in Table 1. These programs
require a version of HyperChem 4.0 or later that
supports DDE. Also required is Microsoft Excel 5.0 or
higher. HyperChem and Excel are not included with the issue.
Ordering and Information
JCE Software is a publication of the
Journal of Chemical Education. There is an order form inserted in this issue that
provides prices and other ordering information. If this card is not available or if you need additional information, contact:
JCE Software, University of Wisconsin-Madison,
1101 University Avenue, Madison, WI 53706-1396 phone: 608/262-5153 or 800/991-5534
fax: 608/265-8094; email: jcesoft@chem.wisc.edu
Information about all of our publications (including abstracts, descriptions, updates) is available from the JCE Software World Wide Web site.
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