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1	Chapter 4 Organic Compounds: Cycloalkanes and their Stereochemistry David Oliver
2	Stereochemistry of Alkanes and Cycloalkanes After this chapter, you should be able to: Define conformer, conformation, conformational Understand ways to draw and represent isomers Discuss relative energies of staggered and eclipsed Discuss ideas and problems with Baeyer strain theory Calculate and discuss the nature of ring strain Discuss consequences of conformational isomerism for alkanes and cycloalkanes
3	Stereochemistry Three dimensional relations of atoms in compounds. Conformational isomers – rotation about single bonds bring about different conformers having different conformations
4	Ethane Conformations Requires ViewerLite Ethane in msv format ethane.msv Ethane rotation movie ethane.htm
5	Ethane: Energy of Conformations
6	Propane Conformations Requires ViewerLite Propane.msv propane Sketch the Newman projection and the energy profile for the rotation of C₃H₈
7	Propane: Energy of Conformations
8	Butane Conformations Requires Viewerlite and QuickTime Butane in pdb format butane.msv Butane rotation movie spacefilled http://chipo.chem.uic.edu/web1/ocol/Movie/but2.htm Butane rotation movie ball and stick http://chipo.chem.uic.edu/web1/ocol/Movie/but3sm.htm
9	Butane Conformers
10	Butane: Dynamics Requires Chem 3D butane.c3d
11	Draw the Newman projection and sketch the energy profile for 360° rotation about the #2-carbon – #3-carbon bond
12	Calculate the total strain energy.
13	Cycloalkane Conformations Angle strain occurs when angles vary from 109°.
14	Calculating Strain A ring can be viewed as (CH₂)_n units. Cyclohexane is the reference substance with no angle strain. (CH₂)₆ with a heat of combustion of 3952 kJ/mole. By comparing heats of combustion per CH₂ unit, the strain for other cycloalkanes can be calculated.
15	Extra Credit: Given a heat of combustion of cyclohexane of 3952 kJ/mole and a heat of combustion of cyclopropane of 2091 kJ/mol, estimate the strain energy of cyclopropane. Show all steps in your calculation.
16	Types of Strain Angle Strain – When C-C-C angle is greater or less than 109° Torsional Strain – Eclipsed hydrogens Steric Strain - crowding
17	Stable Conformation of Cyclobutane, Cyclopentane and Cyclohexane Using Chem3D, show relative conformational energies of cyclobutane, cyclopentane, and cyclohexane. cyclobutane.C3D cyclopentane.C3D cyclohexane.C3D
18	Axial – Equatorial Positions of Cyclohexane
19	Axial – Equatorial Positions of Cyclohexane
20	Monosubstituted Cyclohexanes
21	Disubstituted Cyclohexanes Which conformer is more stable?
22	Disubstituted Cyclohexanes You may need to consider both tables 4.1 and 4.2
23	How many cis-trans and conformational isomers?
24	Boat Cyclohexane Unstable due to eclipsed configuration. Substituents an be made more stable than chain. Can you think of how?
25	Polycyclic Alkanes