91Ó°ÊÓ

Cellulose is water insoluble, despite its many OH groups. Considering its three-dimensional structure, why do you think this is so?

Locate the stereogenic centers in each compound.

a.

b.

Which group in each pair is assigned the higher priority?

a. ${\mathbf{\text{-CH}}}_{\mathbf{3}}{\mathbf{\text{,-CH}}}_{\mathbf{2}}{\mathbf{\text{CH}}}_{\mathbf{3}}$

b. $\mathbf{\text{-I,-Br}}$

c. $\mathbf{\text{-H,-D}}$

d. ${\mathbf{\text{-CH}}}_{\mathbf{2}}{\mathbf{\text{Br,-CH}}}_{\mathbf{2}}{\mathbf{\text{CH}}}_{\mathbf{2}}\mathbf{\text{Br}}$

e. localid="1648296449951" ${\mathbf{\text{-CH}}}_{\mathbf{2}}{\mathbf{\text{Cl,-CH}}}_{\mathbf{2}}{\mathbf{\text{CH(CH}}}_{\mathbf{3}}{\mathbf{\text{)}}}_{\mathbf{2}}$

f.${\mathbf{\text{-CH}}}_{\mathbf{2}}\mathbf{\text{OH,-CHO}}$

Rank the following groups in order of decreasing priority?

a.${\mathbf{\text{-COOH,-H,-NH}}}_{\mathbf{2}}\mathbf{\text{,-OH}}$

b.${\mathbf{\text{-CH}}}_{\mathbf{2}}{\mathbf{\text{CH}}}_{\mathbf{3}}{\mathbf{\text{,-CH}}}_{\mathbf{3}}{\mathbf{\text{,-H,-CH(CH}}}_{\mathbf{3}}{\mathbf{\text{)}}}_{\mathbf{2}}$

c.${\mathbf{\text{-H,-CH}}}_{\mathbf{3}}{\mathbf{\text{,-Cl,-CH}}}_{\mathbf{2}}\mathbf{\text{Cl}}$

d.${\mathbf{\text{-CH=CH}}}_{\mathbf{2}}{\mathbf{\text{,CH}}}_{\mathbf{3}}\mathbf{\text{,°ä≡C±á,-±á}}$

Label each compound as R or S.

a.

b.

c.

d.

Draw both enantiomers of clopidogrel (trade name Plavix), a drug given to prevent the formation of blood clots in persons who have a history of stroke or coronary artery disease. Plavix is sold as a single enantiomer with the S configuration. Which enantiomer is Plavix?

a. Locate the stereogenic centres in the ball-and-stick model of lisinopril, a drug used to treat high blood pressure.

b. Label each stereogenic centre as R or S.

What is the maximum number of stereoisomers possible for a compound with:

a. three stereogenic centers;

b. eight stereogenic centers?

Label the two stereogenic centers in each compound and draw all possible stereoisomers.

a.

b.

Compounds E and F are two isomers of 2,3-dibromopentane drawn in staggered conformations. Which compounds (A–D) in Figure 5.8 are identical to E and F?