Complete the cyclohexane activity we started in class BEFORE returning to class on Wednesday. •We will take a few minutes to regroup, and then I will call on groups for their responses. We will finish Ch. 4 and begin IR on Wednesday. IR will NOT be on Test 2.Test 2 - Friday - everything through Ch. 4 including all nomenclature, UV Vis, aromaticity, ETC....•Old tests and Study guides for all chapters/units except UV-Vis are posted on the organic website•Si changes - see email from Kaitlyn- having sessions Tuesday night and Wednesday night•Ch. 4 Smartwork is now available - not due until after the test, but won't hurt to work them before •the test! :) I recommend prioritizing the textbook homework (below) over the smartwork, but do what helps YOU learn!Test 2 Q&A session Thursday afternoon 3-4 PM. Location TBA•Upcoming office hours: Tuesday 3-4 PM, Wednesday (*change from normal due to a mtg**): 12:00 •pm - 1:15 pm, Thursday 10-11 am + 2-3 pm +Q&A session 3-4 pm, Friday 9-10 am

Textbook Problems and Reading:Reading: Finish reading ch. 4 if you have not already. Read the IR sections in Ch. 15: 15.4-15.15.7Ch. 4 Textbook problems: 4.2, 4.5, 4.7, 4.9, 4.12, 4.13, 4.14, 4.16, 4.17, 4.31, 4.32, 4.33, 4.39, 4.43, 4.65. Problems for additional practice if desired: 4.29, 4.30, 4.34, 4.59, 4.55

Cycloalkane Structures

Power Point slides used in class and cyclohexane activity below these notes. We got about 1/2 way through the cyclohexane activity. Finish it as homework, and we'll get back into groups at the beginning of class wed. I'll call on groups to provide their responses.

Klein: Figure 4.18 p. 164

CxH2x + O2 -> X CO2 + H2O

Chair & Boat Cyclohexane -

Cyclohexane Activities Dr. Blue’s CHEM 227 Class

1) Get in a group of three. Designate one person as the recorder, one person as the spokesperson, and one as the timekeeper. As many people as possible should build/manipulate/handle the models.

2) Start with cyclohexane with hydrogen atoms on one side of the ring, and halogen atoms on the other side of the ring.

a) Make the ring “flat”

i) Rotate the ring so that the hydrogen atoms are pointing “up”

ii) What do you notice about the bonds in the ring when the ring is flat?

iii) Which direction are the halogen atoms pointing?

b) Fold the ring into a chair shape. The easiest way to do this is to push one carbon atom UP relative to the others, and then to push DOWN the carbon atom that is 4 carbon atoms away from the one that was pushed up initially. Check the conformation and adjust until it looks like a lounge chair with a “head” and a “foot” area when held appropriately.

i) Observing the geometry about one of the carbon atoms, what is the molecular geometry about the carbon atom? ___________________________

ii) What would you estimate a H-C-X bond angle to be on this structure? ________________

iii) Do you observe any ring strain in this conformation? How does the ring strain compare to when the ring was in a “flat” conformation?

iv) Hold the ring so that some of the C-H/C-X bonds point straight up and down, and so that the straight up and down C-H bonds are such that the hydrogen atoms are still “up”

v) Are all of the hydrogen atoms still pointing “up”, in general?

vi) Which direction are the halogen atoms pointing, in general?

vii) What pattern do you notice with the hydrogen atoms? What pattern do you notice with the halogen atoms?

viii) Look down one of the C-C bonds of the chair conformation – how would you describe the confirmation in terms of the relative positions of the halogen and hydrogen atoms? Are they staggered or eclipsed? _______________________________

3) Definitions/observation summary:

i) Axial: _________________________________________________

ii) Equatorial: __________________________________________________

iii) Up: _________________________________________________________

iv) Down: _______________________________________________________

v) Atoms that are beside each other, and pointing in the same direction when the cyclohexane ring is flat exhibit what pattern when the cyclohexane ring is in a chair conformation? _________________________________________________________

vi) Cis (in alkane rings): ___________________________________________________

vii) Trans (in alkane rings): ________________________________________________

4) Replace all but 1 of the halogen atoms with hydrogen atoms. Replace the hydrogen atom that is bonded to the same carbon as the remaining halogen atom with another colored atom – such as a blue one. Assume this blue atom is a bromine atom.

a) Name the compound using the IUPAC system: _________________________________

i) Which general direction (up or down), is the halogen atom pointing? ____________

(1) Is the halogen atom axial or equatorial? _____________

ii) Which general direction (up or down), is the bromine atom pointing? ____________

(1) Is the bromine atom axial or equatorial? ____________

b) WITHOUT ROTATING THE MODEL, “Flip” the chair by performing the following operations: 1) find a carbon atom that is generally pointing down, and push it up. 2) Take the carbon atom that is 4 carbon atoms away from the one that was pushed down to up, and push it from up to down. Adjust the ring until it is in the proper conformation.

i) Orient the halogen atom so that it is pointing in the same direction as listed in 4.a.i just above. Which general direction (up or down), is the halogen atom pointing? ____________

(1) Is the halogen atom axial or equatorial? _____________

ii) Which general direction (up or down), is the bromine atom pointing? ____________

(1) Is the bromine atom axial or equatorial? ____________

iii) What happened to the orientations of the atoms after the ring was “flipped”?

5) Replace the bromine with a hydrogen atom, and replace the halogen with a tert-butyl group.

a) “Flip” the chair a few times as described above, which orientation gives the most “space” for the t-butyl group?

b) What happens to the t-butyl group when it is in the other orientation?

6) Place another t-butyl group on the 2 carbon atom (one away from where the first t-butyl group), cis to the first t-butyl group. “Flip” the chair until you arrive at what seems to be the most stable conformation (where the t-butyl groups have the most space):

a) What is the IUPAC name of this structure?: ________________________________________

b) What is/are the general direction of the two t-butyl groups? (up/down): __________________

c) What is/are the orientation (axial/equatorial) of the two t-butyl groups?: ___________________

7) Now change the structure so that the t-butyl groups are trans to one another, but still on neighboring carbon atoms. Again, “flip” the chair until you arrive at what seems to be the most stable conformation (where the t-butyl groups have the most space):

a) What is the IUPAC name of this structure?: ________________________________________

b) What is/are the general direction of the two t-butyl groups? (up/down): __________________

c) What is/are the orientation (axial/equatorial) of the two t-butyl groups?: ___________________