Author Archives: Charles Taylor

CHM 111: Board notes from 1/21/09

Here are the notes from Wednesday’s CHM 111 class. These notes continue our discussion of valence bond theory from Chapter 10, then introduce the phases of matter from Chapter 11.

[CHM 111: 1/21/09 notes]

We discusses several chlorine-containing hydrocarbons during our talk about how double bonds work in valence bond theory.  Here they are.

This is 1,2 dichloroethane. Both ends of this molecule are free to rotate around the C-C bond.

This is 1,2 dichloroethane. Both ends of this molecule are free to rotate around the C-C bond.

This is cis 1,2-dichloroethene. Both of the chlorine atoms are on the same side of the C=C bond. The chlorine atoms are fixed in this position because the double bond does not allow free rotation, since rotation would break the pi component of the double bond.

This is cis 1,2-dichloroethene. Both of the chlorine atoms are on the same side of the C=C bond. The chlorine atoms are fixed in this position because the double bond does not allow free rotation, since rotation would break the pi component of the double bond. This illustration shows electrostatic potential, and we can see that this molecule is polar.

This is trans 1,2-dichloroethene. The chlorine atoms are on opposite sides of the C=C bond. The chlorine atoms are fixed in this position because the double bond does not allow free rotation, since rotation would break the pi component of the double bond. This illustration shows electrostatic potential, and we can see that this molecule is nonpolar. It also has observably different physical properties (like boiling point) from the cis form.

This is trans 1,2-dichloroethene. The chlorine atoms are on opposite sides of the C=C bond. The chlorine atoms are fixed in this position because the double bond does not allow free rotation, since rotation would break the pi component of the double bond. This illustration shows electrostatic potential, and we can see that this molecule is nonpolar. It also has observably different physical properties (like boiling point) from the cis form.

MLK Holiday

Monday 1/19/09 is a holiday.  The school will be closed, and no classes or labs will meet.  Here’s how the holiday will affect your chemistry schedule.

CHM 100 students

  • No lecture on Monday 1/19
  • Section 1 lab will not meet on 1/19.  You will perform the introductory experiment on 1/26.
  • Section 2 lab will meet on Tuesday 1/20.  You will perform the introductory experiment.  I will hand out a copy of the experiment when you get to lab, but if you want to look it over before coming in, here it is: [CHM 100 Introductory Experiment]

CHM 110 students

  • Your class schedule is unaffected by the holiday.  You will perform the introductory experiment (the same one as the CHM 100 class) on Thursday 1/22.

CHM 111 students

  • No lecture on Monday 1/19
  • You will perform Experiment 9B on Wednesday 1/21.  Remember that the prelab for the experiment (pages 177-178 inyour lab manual) is due at the beginning of the lab period.  Please have it ready when you walk in.  Also, don’t forget your lab manual and notebook on Wednesday.

CHM 111: Board notes for 1/14/09

Here are the notes from today’s CHM 111 class.  These notes discuss polarity and molecular shape, and introduce valence bond theory.

[CHM 111: 1/14/09 notes]

Here area few 3D renderings of some of the molecules we discussed in class.  You can click each image for a larger version.

You can see that each of propane's three carbon atoms have a tetrahedral geometry.

You can see that each of propane's three carbon atoms have a tetrahedral geometry.

Ethanol's two carbons are both tetrahedral, while the geometry around the oxygen atom is bent (a derivative of tetrahedral).

Ethanol's two carbons are both tetrahedral, while the geometry around the oxygen atom is bent (a derivative of tetrahedral).

This molecule is polar, since fluorine is able to draw electrons towards itself.

This molecule is polar, since fluorine is able to draw electrons towards itself. This picture is shaded to show electrostatic potential: blue for negative, and red for positive.

Even thought it's not immediately obvious from the Lewis structure (see the notes for the structure), this molecule is polar. In three dimensions, you can clearly see that the fluorine atoms are on the same side of the molecule.

Even thought it's not immediately obvious from the Lewis structure (see the notes for the structure), this molecule is polar. In three dimensions, you can clearly see that the fluorine atoms are on the same side of the molecule.