More Practice Problems on Stereochemistry 1. For each of the following compounds, identify all stereogenic centers and

designate their absolute configurations using the R/S system.

2. Which of the following molecules are chiral? Which are meso?

O

N

N

O

H

H H

H

H

(-)-strychnine

OH

OH

OH

HO

O

OH

α-D-galactopyranose

H3C

H

OH

grandisol

NCH3

O

O

C6H5

H

CO2CH2CH3

H

H

H

cocaine

Br

H

Cl

Cl

H

H

Cl

Cl

H

H

HO2C CO2H

OH

OH

OHOH

OHHO

OH

OH

OH

OH

3. In each of the following, indicate whether the indicated groups or atoms are homotopic or heterotopic. For those that are heterotopic, designate them as enantiotopic or diastereotopic.

O

H

H

CH3

H H

CH3

H3C OO

HH

Answers to “More Practice Problems on Stereochemistry”

1) Identification of stereogenic centers and naming as R/S.

O

N

N

O

strychnine cocaine

OH

OH

OH

HO

O

OH

α-D-galactopyranose

CH3

H

OH

H H

H

H

H

N

O

O

Ph

CO2Me

H

H

H

grandisol

RS

R

R

S

R

R

S

S

R

S

2) Identification of chiral structures, and difference between meso and simple achiral structures.

Br

H

this is simply achiral

Cl

Cl

H

H

Cl

Cl

H

Hboth of these are achiral

HOOC COOH

OH

OH

OH

this is chiral

OH

this is also chiral

HOOH

OH

OH

OH

OHthis is a meso compound

3) Homo/heterotopicity and diastereo/enantiotopicity.

OH

H

these are enantiotopicH H

these are diastereotopic

CH3

H3C

the methyls are homotopic

OO

HHthese are enantiotopic