What is meant by retardation factor?

(i) ${\mathrm{CH}}_3-\mathrm{CH}={\mathrm{CH}}_2+\mathrm{HBr}$ $\stackrel{{\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{O}\right)}_2{\mathrm{O}}_2}{\to }$ $\left(\mathrm{A}\right)$

(ii) ${\mathrm{CH}}_3-\mathrm{CH}={\mathrm{CH}}_2+\mathrm{HBr}$$\stackrel{}{\to }\left(\mathrm{B}\right)$

The type of isomeric relation between $\left(\mathrm{A}\right)$ and $\left(\mathrm{B}\right)$ is ?

How would you convert the following compound into benzene?

Ethyne.

How would you convert the following compound into benzene?

Ethene.

Write the number of $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds in the following molecules?

$\left(\mathrm{a}\right)$ 

$\left(\mathrm{b}\right)$ 

$\left(\mathrm{c}\right)$ 

Find the number of $1°, 2°$ and $3°$ hydrogen atoms in the following compounds.

$\left(\mathrm{a}\right)$ 

$\left(\mathrm{b}\right) {\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

$\left(\mathrm{c}\right)$ ${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3$