To determine the priority of various functional groups compared to the hydroxyl group (-OH), we apply the Cahn-Ingold-Prelog priority rules. These rules are used to assign priorities based on the atomic numbers of atoms directly attached to the chiral center, and then further distances if necessary.
Let's analyze each group:
A. -CHCH3 (methyl): This group is an ethyl group where one hydrogen is substituted by another methyl group. The central carbon is directly bonded to another carbon and two hydrogens (since the molecular structure would look like this: CH3-CH-CH3). When compared to a hydroxyl group (which has oxygen directly bonded to carbon), oxygen has a higher atomic number than carbon.
B. -CH₂OH (hydroxymethyl): This group is composed of a carbon directly bonded to an oxygen (through a hydroxyl group) and two hydrogens (since the structure is CH2OH). Here, we see that oxygen (atomic number 8) has a higher atomic number than carbon.
C. -Br (bromo group): This group involves a bromine atom directly bonded to the carbon atom. Bromine has a much higher atomic number (35) compared to oxygen.
So, according to these priorities:
- Bromine (Br) has the highest atomic number among the three options, therefore giving the bromo group the highest priority.
- Next comes hydroxyl group (OH) due to the oxygen atom.
- Then comes hydroxymethyl group due to the direct oxygen bond.
- Lastly, the ethyl group due to it being only carbon and hydrogen.
Thus, the group that shows higher priority compared to the hydroxyl group among the given options is:
C. -Br
