Question

Calculate the oxidation no. of underlined elements in $\underset{–}{C}{H}_3\underset{–}{C}{H}_{2}OH$

Answer 1

For the C atom of methyl group, each H has +1 oxidation number. 3 H atoms of methyl group in total have +3 oxidation number. The oxidation number of C atom of methyl group will be -3 as it will balance the total oxidation number of 3 H atoms.
For the C atom of methylene group, each H has +1 oxidation number and -OH group has -1 oxidation number. The oxidation number of C atom of methylene group will be -1 as it will balance the total oxidation number of 2 H atoms and one -OH group.
Note: The average oxidation number of C atom is as calculated below.
Let X be the oxidation state of C in $C{H}_{3}C{H}_2-OH$.
$2X+6(+1)-2=0$
$X=-2$
Hence, the oxidation state of C in $C{H}_{3}C{H}_{2}OH$ is -2.