91Ó°ÊÓ

Primary hydrogen is hydrogen that resides on a carbon which is only attached to one carbon atom.

Secondary hydrogen is hydrogen that resides on a carbon which is only attached two carbon atoms.

Tertiary hydrogen is hydrogen that resides on a carbon which is only attached to three carbon atoms.

Primary and secondary hydrogen in isopentane

$(2-\mathrm{methylbutane})$

There are nine primary $\left(1^0\right)$ hydrogen, two secondary $\left(2^0\right)$ hydrogen, and one tertiary $\left(3^0\right)$ hydrogen in isopentane .$(2-\mathrm{methylbutane})$

chlorination of isopentane

$(9  \mathrm{primary}  \mathrm{hydrogens})×(\mathrm{reactivity}  1.0)= 9.0  \mathrm{relativeamountofreaction}$

$(2  \mathrm{secondary}  \mathrm{hydrogens})×(\mathrm{reactivity}  4.5)= 9.0  \mathrm{relativeamountofreaction}$

Now,

$\mathrm{fractions}  \mathrm{ofprimary} = \frac{9.0}{9.0+9.0+5.5}=\frac{9.0}{23.5}=38.3 \%$

$\mathrm{fractions}  \mathrm{ofsecondary} = \frac{9.0}{9.0+9.0+5.5}=\frac{9.0}{23.5}=38.3 \%$

$\mathrm{fractions}  \mathrm{oftertiary} = \frac{5.5}{9.0+9.0+5.5}=\frac{5.5}{23.5}=23.4 \%$

Hence, the products formed will be in the ratio$38.3 \%  :  38.3  \%  :23.4 \%$