A graphic of a polarimeter is shown, along with three movable sliders that allow the user to vary the concentration of each of the three stereoisomers of tartaric acid. The plane of polarized light twists more and more as the concentration of one of the chiral isomers is increased, and the plane rotates in the opposite direction for the other enantiomer. Changing the concentration of the meso isomer has no effect on the rotation.
Type of Material:
The material is an animation/simulation.
This material is recommended for use in undergraduate Organic Chemistry classes as an ancillary. This would be a nice simulation to show in class when discussing the theory of optical activity. There are only three variables so the entire functionality of the simulation can be explored fairly quickly.
This virtual polarimeter requires the user to download Wolfram CDF player in order to use it. The download is free, very simply and does not consume much space on the hard drive.
Identify Major Learning Goals:
Visualization of optical activity. Demonstrates the relationship of specific rotations between isomers, and the variation with concentration (and, presumably, path length since the twisting of the plane of light is gradual).
Target Student Population:
The course that this material targets is Organic Chemistry. It can be used for Organic I or Organic II depending on the curriculum.
Prerequisite Knowledge or Skills:
A student using this should have a basic knowledge of enantiomers and diastereomers; they should have a basic knowledge of optical activity and what it measures (i.e. one lecture or portion of a lecture should suffice); they should have basic computer skills and a student using this software should be able to identify changes in the graphical representation of plane polarized light as the simulation show the plane-polarized light being rotated in real time.
The software is very easy to use. It is easliy translateable to use in an analytical chemistry course or an instrumental analysis course because of the technical details of how the polarimeter actually works.
The text that accompanies the simulation is quite dense and rich in jargon. It would be more useful if it were simplified and broken down into smaller chunks of information. While the simulation is for beginners, the explanation is highly advanced.
Potential Effectiveness as a Teaching Tool
This simulator does not explicitly deliniate learning goals but the technical aspect of the overview is very well written. Students that are seeking a deeper understanding of optical activity will find this as helpful. It seems geared towards a more advanced treatment of what a textbook would offer. It may be helpful to add that to the initial paragraph of the overall description.
The learning goals are implicit and need to be stated if it is a required tool for coursework. The simulator should be expanded to include more molecules if possible. The formula for calculating the specific rotation is given, but no examples are provided and the explanation would be difficult for beginning students to follow.
Ease of Use for Both Students and Faculty
This simulator is very easy to use once the Wolfram CDR is downloaded.
There is no play-by-play breakdown of exactly what is being shown so the user may miss some details. For example, the polarimeter gets darker as the sample is more concentrated - but that may be confused with the blocking of the light that occurs when using a polarimeter (there is no explanation of what the darker shades mean). The "snapshots" would be more useful if each had detailed observations included (i.e., note that the 1:1 mixture of two enantiomers, called a racemic mixture, have an overall rotation of zero degrees).
Other Issues and Comments:
I do not have any other issues. I think this is a very user friendly simulation and with some tweaking to the instructions, will be very helpful to students when they are studying optical activity.
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