Background

The ability to represent chemical structures and to produce reaction mechanisms is an important part of modern chemistry, especially organic chemistry.  In this exercise you will use ChemDraw and Chem3D to show chemical structures and some reaction mechanisms.  You will also use these computer programs during the semester so that you can include chemical structures in your written reports.

The following reactions or reaction mechanisms are from Experiment I.  These diagrams were originally drawn using ChemDraw.  Using this computer program, you can adequately represent the chemical pathways and show mechanisms to understand reactions better.  You will use these programs to draw structures and to include structures in your written reports.

First Day:

1. For this exercise, you will use ChemDraw to display each of the following (text label each structure):

2. Draw reaction mechanisms (show entire reaction, including reactants and products) for the first two reactions below:

• S_N2 nucleophilic substitution of 2-bromobutane with OH^– ion (no carbocation is formed)
• OH^– ion addition to a bromonium ion (produces a halohydrin)
• Show the reaction between ethanol and ethanal (in presence of acid) showing the hemiacetal product (your instructor will show you the structure of the product; please, no reaction mechanism for this reaction)

3. Using Chem3D, show energy minimized drawings for trans- and cis-2-butene.  Using the drawing tools in Chem3D, it is easy to draw these structures. First, draw the double bond using the double-bond tool. Second, using the single bond tool place the end carbons onto each of the carbons of the double (for cis, show the two methyl groups on same side, but for trans place the methyl groups on opposite sides).

• It is best to draw these structures in ChemDraw and transfer the image to Chem3D.
• Minimize the structure using the MM2 option from the drop-down menu. Using the rotation tool show a perspective that is pleasing to your eye and shows clearly the structure of the molecule.
• Copy each image by selecting all atoms and then copy back to the ChemDraw page. You can size the image to make it smaller in ChemDraw.  Follow the same procedure for the other structure.  This way, you can label your structures and put your names on the printed page, from ChemDraw, which you cannot do from Chem3D.

Second Day:

During the second day of this lab, you will individually do a short quiz using ChemDraw and Chem3D. You will work alone, and will have 60 min to finish this quiz (with a 10 minute grace period). Students will sign up for one of the three different start times. Come to the lab for your pre-assigned time. This exercise will count as a regular quiz, not as a lab score.