Assign priorities to the groups in each set. (a) \(-\mathrm{H}-\mathrm{CH}_{3}-\mathrm{OH}-\mathrm{CH}_{2} \mathrm{OH}\) (b) \(-\mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}_{3}-\mathrm{CH}_{2} \mathrm{COOH}\) (c) \(-\mathrm{CH}_{3}-\mathrm{H}-\mathrm{COO}^{-}-\mathrm{NH}_{3}{ }^{+}\) (d) \(-\mathrm{CH}_{3}-\mathrm{CH}_{2} \mathrm{SH}-\mathrm{NH}_{3}^{+}-\mathrm{CHO}\)

In each group, identify the atoms directly connected to the chiral center. In this case, the chiral center is the central atom.

Assign priorities to the atoms connected to the chiral center based on their atomic numbers. Remember that a higher atomic number corresponds to a higher priority. (a) \(-\mathrm{H}-\mathrm{CH}_{3}-\mathrm{OH}-\mathrm{CH}_{2} \mathrm{OH}\) H: 1, C: 6, O: 8. Priorities: O>H>C (b) \(-\mathrm{CH}_{2}\mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{COOH}\) C: 6, C: 6, C: 6, C: 6. All carbon atoms have the same atomic number, so we need to look further outward to break the tie.

If there is a tie between atoms with the same atomic number connected to the chiral center, continue moving outwards along the chain of atoms until the tie is broken. For group (b), \(-\mathrm{CH}_{2}\mathrm{CH}=\mathrm{CH}_{2}\): connected to C with double bond \(-\mathrm{CH}=\mathrm{CH}_{2}\): connected to C with single bond \(-\mathrm{CH}_{3}\): connected to C \(-\mathrm{CH}_{2}\mathrm{COOH}\): connected to C and O Priorities: \(-\mathrm{CH}_{2}\mathrm{COOH}>-\mathrm{CH}_{2}\mathrm{CH}=\mathrm{CH}_{2}>-\mathrm{CH}=\mathrm{CH}_{2}>-\mathrm{CH}_{3}\) (c) \(-\mathrm{CH}_{3}-\mathrm{H}-\mathrm{COO}^{-}-\mathrm{NH}_{3}{ }^{+}\) H: 1, C: 6, O: 8, N: 7. Priorities: O>N>C>H (d) \(-\mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{SH}-\mathrm{NH}_{3}^{+}-\mathrm{CHO}\) C: 6, C: 6, S: 16, N: 7. Priorities: S>N>C In conclusion, the priorities for each group are: (a) \(-\mathrm{H}-\mathrm{CH}_{3}-\mathrm{OH}-\mathrm{CH}_{2} \mathrm{OH}\) Priorities: O>H>C (b) \(-\mathrm{CH}_{2}\mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}-\mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{COOH}\) Priorities: \(-\mathrm{CH}_{2}\mathrm{COOH}>-\mathrm{CH}_{2}\mathrm{CH}=\mathrm{CH}_{2}>-\mathrm{CH}=\mathrm{CH}_{2}>-\mathrm{CH}_{3}\) (c) \(-\mathrm{CH}_{3}-\mathrm{H}-\mathrm{COO}^{-}-\mathrm{NH}_{3}{ }^{+}\) Priorities: O>N>C>H (d) \(-\mathrm{CH}_{3}-\mathrm{CH}_{2}\mathrm{SH}-\mathrm{NH}_{3}^{+}-\mathrm{CHO}\) Priorities: S>N>C