Which of the following assignment of priorities is not correct?

Options

A. `(CH_(3))_(3)C-`has higher priority than `(CH_(3))_(2)CH-`
B. `C_(2)=CH-`has higher priority than `(CH_(3))_(2)CH-`
C. `(CH_(3))_(3)C-`has higher priority than `HC = C-`
D. `-CH=O` has higher priority than `HC =C-`

Answer

C

Explanation

`HC -=C-` equals `H-overset((C))overset(|)underset((C))underset(|)C-overset((C))overset(|)underset((C))underset(|)C-` and takes priority
`over-overset(CH_(3))overset(|)underset(CH_(3))underset(|)C-CH_(3)`
(1) `t`-Buty`1` has three methy`1` groups bonded to the carbon atom giving it priority over isopropy`1` which has two methy`1` groups and an `H`.
(2) `-CH=CH_(2)` equal `-overset((C))overset(|)underset(H)underset(|)C-overset((C))overset(|)underset(H)underset(|)C-H`and takes priority over
`-overset(H)overset(|)underset(CH_(3))underset(|)(C)-CH_(3)`
Note that at the first `C` bith viny`1` and isopropy`1` groups are `C,C,H`. Therefore we move to the next atom in the chain
(4) `-CH=O`equals`-overset((O))overset(|)underset(H)underset(|)C-underset((C))underset(|)O`and takes priority over
`HC -=C-` which is equal to `-overset((C))overset(|)underset((C))underset(|)C-overset((C))overset(|)underset(H)underset(|)C-(C)`