Like carvone, the two enantiomers of celery ketone smell differently. The R enantiomer smells like celery leaves, whereas the S enantiomer smells like licorice. Draw each enantiomer and assign its odor.

Explain how bacteria avoid osmotic rupture.

Name two beneficial uses of bacteria.

Are $\alpha$-D-glucose and $\beta$-D-glucose enantiomers? Explain your choice.

The following reactions give a mixture of two stereoisomers. Write their structures. Are they enantiomers or diastereomers? Are they chiral or achiral? Are they formed in equal amounts?

(a) $\mathrm{BrCH}_2 \mathrm{CH}_2 \mathrm{Br}+\mathrm{Cl}_2 \stackrel{\text { light }}{\longrightarrow} \mathrm{C}_2 \mathrm{H}_3 \mathrm{Br}_2 \mathrm{Cl}+\mathrm{HCl}$

(b) CC1CCC(C)(O)CC1

$$\stackrel{\mathrm{HCl}}{\longrightarrow}$$

(c) CC1(C)CCCC(C)(O)C1

$$\stackrel{\mathrm{HCl}}{\longrightarrow}$$

Which of the amines listed next can be resolved into enantiomers? In each case, explain why interconversion of the enantiomers would or would not take place. (a) cis-2-methylcyclohexanamine (b) N-ethyl-N-methylcyclohexanamine (c) N-methylaziridine (d) ethylmethylanilinium iodide (e) methylethylpropylisopropylammonium iodide

Explain the following terms: (a) enantiomers, (b) racemic mixtures.

Which molecule can have enantiomers?

(A) CH$_4$

(B) CF$_2$H$_2$

(C ) CFCIBrI

(D) CF$_2$CIH

Are $\mathrm{D}$-fructose and $\mathrm{L}$-fructose enantiomers? Explain your choice.

Explain how antibiotics kill bacteria.

Draw the structures of all possible diastereoisomers of an octahedral complex with the formula $\mathrm{MA}_2 \mathrm{B}_2 \mathrm{C}_2$. Which of the diastereoisomers, if any, can exist as enantiomers?

Although one enantiomer of the drug thalidomide is a sedative, the other is teratogenic (causes birth defects). Unfortunately, thalidomide is racemized in the body and, for that reason, both enantiomers are teratogenic. Assuming the availability of acids and bases as needed, give a curved-arrow mechanism for the base-catalyzed racemization of thalidomide in water.

Both enantiomers and diastereomers are stereoisomers. How do they differ?

Are L-alanine and D-alanine enantiomers?