E4 Prelab Ans

EXPERIMENT #4 – MOLECULAR MODELING PART II Prelab 1. Write both chair conformations for cis-1,3- and trans-1,3-dimethylc...

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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