Which of the following groups has the highest priority according to the Cahn-Ingold-Prelog sequence rules? ans. CH2Cl CHO CH3 CH2OH

The Cahn-Ingold-Prelog (CIP) sequence rules are used to assign priority to different groups attached to a chiral center in a molecule. The rules are as follows:

1. Atoms attached to the chiral center are ranked according to their atomic number. The atom with the highest atomic number gets the highest priority.

2. If two atoms attached to the chiral center have the same atomic number, then the next atoms in the attached groups are considered. This continues until a difference is found.

3. If a double or triple bond is present, the atom(s) involved in the bond are considered to be duplicated or triplicated for the purposes of ranking.

Using these rules, we can rank the given groups:

• CH2Cl: The first atom is carbon (atomic number 6), and the next atom is chlorine (atomic number 17).

• CHO: The first atom is carbon (atomic number 6), and the next atom is oxygen (atomic number 8).

• CH3: All atoms are carbon (atomic number 6).

• CH2OH: The first atom is carbon (atomic number 6), and the next atom is oxygen (atomic number 8).

So, according to the CIP rules, the group with the highest priority is CH2Cl, because it contains chlorine, which has the highest atomic number among the atoms considered.