Which group in each pair has the highest priority? a) -CH_(3) or -CH_(2)CH_(3) b) -1 or -Br c) -CH_(3)Br or -CH_(2)CH_(2)Br

a) In the pair $-CH_{3}$ or $-CH_{2}CH_{3}$, $-CH_{3}$ has the highest priority. This is because $-CH_{3}$ is a primary alkyl group, while $-CH_{2}CH_{3}$ is a secondary alkyl group. According to the IUPAC priority rules, primary alkyl groups have higher priority than secondary alkyl groups.<br /><br />b) In the pair $-1$ or $-Br$, $-Br$ has the highest priority. This is because $-Br$ is a halogen atom, while $-1$ is not a valid chemical group. According to the IUPAC priority rules, halogen atoms have higher priority than non-halogen atoms.<br /><br />c) In the pair $-CH_{3}Br$ or $-CH_{2}CH_{2}Br$, $-CH_{3}Br$ has the highest priority. This is because $-CH_{3}Br$ is a primary alkyl halide, while $-CH_{2}CH_{2}Br$ is a secondary alkyl halide. According to the IUPAC priority rules, primary alkyl halides have higher priority than secondary alkyl halides.