Question

Identify the correct option
According to $CIP$ sequence rule, the correct arrangement in order of decreasing priority is:
A. $-OH>C{H}_{2}OH>-CHO>-COOH$
B. $-OH>COOH>-CHO>-C{H}_{2}OH$
C. $-COOH>OH>-COH>-C{H}_{2}OH$
D. $COOH>-CHO>-C{H}_{2}OH>-OH$

Answer 1

Hint:
The higher the atomic number of the immediate substituent atom, the higher the priority.
For example:
$H-<C-<N-<O-<Cl-$

Complete step by step answer:
-The $CIP$ rule is a standard process used in organic chemistry to completely and unequivocally name a stereoisomer of a molecule.
-Priority is numerically assigned as $1,2,3$ and $4$ where smaller the number higher will be the priority. So, $1$ has the highest priority and $4$ has the lowest priority.
Rules for giving the priority:
Rule$1$: Atoms having greater atomic number is given more priority
$-OH\Rightarrow \text{First}$
Atomic number of $\text{0}$ is $8$.
Rule $2$: If $1^{st}$ atom is the same then, see $2^{nd}$ atom and apply Rule $1$.
Rule $3$: For multiple bond
I
II

Break multiple bonds and add one more same atom to that. After this apply Rule$1$ and Rule $2$.
So, the answer is $-OH>COOH>-CHO>-C{H}_{2}OH$
This is the decreasing priority order.
Multiple bonds are treated as separate single bonds.

Note: $-CH=O$ is given priority over $-C{H}_{2}OH$
$I>Br>Cl$
$OH>N{O}_2>N{H}_2>COOH>CHO>C{H}_2$
In geometric isomers:
$Z-\text{isomer > }E-\text{isomer}$