Problem Set 4 - Chem2O6

Chem2O6 - 1997/87

Problem Set #4 October 10, 1997

1. Give IUPAC names for the following structures:

2. Draw structures for the following compounds:

    (a) 1-chloro-2,2-dimethylpentane
    (b) 3-(1,1-dimethylethyl)hexane
    (c) 4-propylheptane
    (d) 2-bromo-3-chloro-5-(2-methylpropyl)dodecane

3. Draw Newman projections of 2,3-butanediol looking down the 2,3-bond. Which is the most stable conformation?

If a gauche OH-OH interaction is worth 1.6 kJ/mol, a gauche CH₃-CH₃ interaction 3.5 kJ/mol, and a gauche CH₃-OH interaction 2.0 kJ/mol, how much more stable is your selected conformation above than the least stable conformer?

4. Construct a model of trans1,4-dibromocyclohexane in its lower energy conformation. What is the orientation of the two C-Br bonds (i.e., axial or equatorial)?

Invert the chair into the alternate chair. What is the orientation of the two C-Br bonds now? Identify any 1,3-diaxial interactions present in both conformers.

5. The equatorial conformer of ethylcyclohexane is 7.4 kJ/mol more stable than the conformer in which the ethyl group is axial. Calculate the percentage of ethylcyclohexane molecules which are in the equatorial conformation at 25^oC.

6. Use the following stereostructural formulas to determine if the compounds are cis or trans geometric isomers. Indicate if the more stable conformer has been drawn for each case. Convert the structures to planar projection formulas using the dash-wedge method for depicting stereochemistry.

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10oct97; wjl