Show You Know! C H 3 CH 3 NH Identify any lines of internal symmetry within the molecules below.

Transcription

1 classroom a c t i v i t y 6 hirality Show You Know!. Identify any lines of internal symmetry within the molecules below. Based on what you have just learned about chirality, could any of these molecules be chiral? (Remember chiral is just Greek for having qualities similar to the human hand.) o, they have internal planes of symmetry, and could be superimposed.. For each of the following compounds: identify any stereogenic centers, assign absolution configuration to those stereogenic centers, identify any plane of symmetry, and indicate whether the molecule is chiral. a. R R hiral molecule, no plane of symmetry. hiral carbons shown with stereochemistry. (R,R)-cyclopentane-,-diol c. Achiral molecule, no chiral carbons plane of symmetry as shown -methylcyclopentanol

2 e. Achiral molecule, no chiral carbons plane of symmetry as shown -methylcyclohexanol g. hiral molecule, no plane of symmetry. hiral carbons shown with absolute configuration. S R (R,S)--methylcyclopentanol 5. For each of the following compounds: Indicate with an asterisk any chiral centers in the molecules. Rank each group on the chiral centers from high to low priority. Determine whether the chiral center is (R) or (S). a. c. l F *S (R)-but--en--ol (S)--chloro--fluoroethane e. LSD g. Ecstacy (MDMA)

3 6 hirality 6. Provide a proper IUPA name for each of the following molecules including any stereochemical designations (R,S or E,Z) a Br l c F d b a. (R,5R)-5-bromo--chloroheptane c. (R,5R)-,5-dimethylcyclohexene hallenge! Warning! ot for the faint of heart; this one is more challenging than would ever be given to you on a test. It is only provided as a challenge. For the following compound: Indicate with an asterisk any chiral center. Rank each group on the chiral centers from high to low priority. Determine whether the chiral center is (R) or (S). Estrogen analog

4 We will first look at what is known as the 7 carbon in estrogen nomenclature... ighest priority () connected to three carbons is it or priority? To determine which is and, we need to look at what each carbon connected to carbons is connected to: connected to three carbons is it or priority? lowest priority () Blue carbon is bonded to carbon with a "real" substitutent and carbons with no substituents Red carbon is bonded to carbons that each have "real" substitutents; it has priority. We have the groups prioritized we can look at what the stereochemistry is. ne problem we have is that the lowest group is in the plane of the page, neither back or front. We need to rotate the molecule. Look from this direction Look from this direction Simplified structure Rotate Pseudo ewman lockwise so R configuration

5 6 hirality So, now it is easy to see that the nomenclature for these molecules usually refers to anything above the ring as α and anything below the ring is β rather than R or S. ow, let s look at the carbon next to it: the carbon. It appears to be connected to other carbons. Lowest priority arbon with a and attached, rd priority arbon with an, a and an attached, st priority arbon with and an, nd priority Rotate Psuedo ewman ounterclockwise so S Let s look at arbon now. This one is relatively easy. Pseudo ewman ounter clockwise=s

6 Let s look at carbon 8. This is another bear, but priority is easy! bonded to s, all with real substituents with s and an with and a bonded to s but not all have real substituents with s and an with and, priority! with and a Rotate Psuedo ewman lockwise R configuration with and, priority with attached, priority with and an, priority Finally carbon 9, priority is easy again Pseudo ewman ounterclockwise, S configuration