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Which of the following would be ranked as the highest priority group?

Group of answer choices

-Cl

-CH2CH3

-NH2

-OH

1 answer

To determine the highest priority group among the given options (Cl, CH2CH3, NH2, OH), we can refer to the Cahn-Ingold-Prelog priority rules, which are used primarily in stereochemistry.

Here's a brief evaluation of each group based on their atomic number at the first point of difference:

  1. Cl (Chlorine) - Atomic number 17.
  2. CH2CH3 (Ethyl group) - Carbon (C) is the highest priority atom here with an atomic number of 6, and since there are two carbon atoms, it will be compared based on the connectivity, but generally, it ranks lower than halogens.
  3. NH2 (Amino group) - Nitrogen (N) is the highest priority atom here with an atomic number of 7.
  4. OH (Hydroxyl group) - Oxygen (O) is the highest priority atom here with an atomic number of 8.

Based on their highest atomic numbers:

  • OH (Oxygen) is the highest priority.
  • NH2 (Nitrogen) comes next.
  • Cl (Chlorine).
  • CH2CH3 (Ethyl group) ranks the lowest.

Therefore, the highest priority group among the given choices is -OH (Hydroxyl group).