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One of the ongoing challenges in teaching chemistry is helping students explore
various structural features of molecules. It can be difficult for students
to visualize the three-dimensional shape of a molecule from a two-dimensional
printed image. Using a molecular modelling kit in the classroom helps,
but such models can be difficult for students to see when demonstrated
by an instructor. These difficulties are more pronounced in teaching symmetry,
especially recognition of various symmetry elements within a molecule and
conceptualization of the symmetry operations.
3D Molecular Symmetry Shockwave is a Web-based application
for interactive visualization and three-dimensional perception of molecular
symmetry. The user interface is simple, and students learn how to use
the program from the built-in help screens. The animation uses the Macromedia
Shockwave browser plug-in, and requires a download of only 256 KB, allowing
it to be used even with low bandwidth Internet connections. Its performance
is comparable to a desktop application.
With 3D Molecular Symmetry Shockwave students and instructors
can:
- Display molecules in ball-and-stick or wireframe representation
- Display each symmetry element of a molecule in a 3D environment and
animate the corresponding symmetry operation
- Rotate, translate, or zoom a molecule to any viewpoint
- Store and recall preferred viewpoints of the molecule for later use
- View information about the selected molecule, its symmetry elements
and its point group
3D Molecular Symmetry Shockwave also serves as a searchable
database of structural and symmetry data for 47 organic and inorganic
molecules, including all symmetry point groups of chemical interest.
This database can be accessed in two modes. In the Symmetry Elements
mode the user can search the database to find all molecules having symmetry
elements of a certain type (for example Cn) or a
particular symmetry element (σv). In the Point
Groups mode the user can search the database to find all molecules having
a point group of a certain type (Cnh) or a particular
point group (D2d).
Figure 1. The main screen from Symmetry
Elements mode of 3D Molecular Symmetry Shockwave.
The main screen from Symmetry Elements mode is shown in Figure 1. A
user has searched the database to find all molecules having C3 rotation
axes. She has selected cubane from the results, and one of its six C3 rotation
axes, and is ready to start the animation of this symmetry operation.
Figure 2. The main screen from Point
Groups mode of 3D Molecular Symmetry Shockwave.
The main screen from Point Groups mode is shown in Figure 2. A user
has searched the database to find all molecules having point groups of
Dnd type. He has selected ferrocene from the list of molecules, and one
of its two C5 rotation axes, and is ready to start
the animation.
3D Molecular Symmetry Shockwave is suitable for undergraduate
students in chemistry, and can be used with typical textbooks (1, 2)
as a self-paced learning tool, as well as a presentation tool.
Symmetry Elements and Operations and Symmetry and Point
Groups are similar programs for Mac OS and Windows respectively,
previously published by JCE Software (3, 4).
However, they have limited capabilities of manipulating a molecule
and its symmetry elements in a 3D environment. Also, they do not have
a database of molecules that can be searched according to specific
symmetry criteria. On the other hand, Symmetry and Point Groups does
lead students through a flow chart of questions to help them identify
the point group of a molecule, a feature that is not available in 3D
Molecular Symmetry Shockwave.
Literature Cited
- Douglas, B. E.; Holingsworth, C. A. Symmetry in Bonding and Spectra,
An Introduction; Academic Press: New York, 1985.
- Cotton, F. A. Chemical Applications of Group Theory, 2nd
ed.; John Wiley & Sons: New York, 1971.
- Vining, William J.; Grosso, Robert P., Jr. J.
Chem. Educ. 2003, 80, 110.
- Lee, A. W. M.; Leung, K. M.; Kwong, D. W. J.; Chan, C. L. J.
Chem. Educ. Software 8C2.
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