91Ó°ÊÓ

The groups with high molecular masses are placed at the first priority. The order of the priority of some groups is:

$\text{H<C<F<Cl<Br<I}$

a. The${\text{-CH}}_2{\text{CH}}_3$ has the highest priority because, in this group, one H is replaced by the one C.

b. The $\text{-I}$has more molecular mass than the Br group. Therefore, the I is given as the highest priority.

c. The $\text{-D}$has more molecular mass than the H group. Therefore, the D is given the highest priority.

d. The ${\text{-CH}}_2\text{Cl}$is given as the highest priority. The Br group comes first in the given group and has more molecular mass than C.

e. The ${\text{-CH}}_2\text{Br}$is given as the highest priority. The Cl group comes first in the given group and has more molecular mass than C.

f. The $\text{-CHO}$is given as the highest priority. The C=O group comes first in the given group and has more molecular mass than C-H.