EXPERIMENT #4 – MOLECULAR MODELING PART II Prelab 1. Write both chair conformations for cis-1,3- and trans-1,3-dimethylcyclohexane. Label each conformer as chiral or achiral. Are the cis-1,3- conformers diastereomers or enantiomers of each other? What about the trans-1,3- conformers? CH3 CH3 H3C
CH3
cis-1,3-dimethylcyclohexane both groups are equatorial meso compound, achiral
cis-1,3-dimethylcyclohexane both methhyl groups are axial meso compound, achiral
These conformers are diastereomers.
CH3 CH3
H3C
CH3
trans-1,3-dimethylcyclohexane one group is axial, and one is equatorial chiral (as drawn, this is R,R)
trans-1,3-dimethylcyclohexane one group is axial, and one is equatorial chiral (as drawn, this is R,R)
These conformers are identical to each other (superimposable)
2. Look up the pKa values of ethane, ethylene, acetylene, acetic acid, trifluoroacetic acid, trichloroacetic acid, ethanol, and phenol. Record these values in your notebook. Compound
pKa
Ethane Ethylene Acetylene Acetic acid Trifluoroacetic acid Trichloroacetic acid Ethanol Phenol
50 – 60 44 25 4.8 0.2 0.8 16 10.0
