Write the name and structure of an aldehyde with four carbon atoms in its molecule.

What is the monomer unit of Teflon?

Identify the compounds $A$ to $E$ in the following reaction sequence:
$(i)$ $CH_3CH_2OH \xrightarrow[dil. HCl]{KMnO_4/KOH} (A) + H_2O$
$(ii)$ $CH_3CH_2OH + A \xrightarrow[\Delta]{Conc. H_2SO_4} B + H_2O$
$(iii)$ $B + NaOH \rightarrow C + CH_3CH_2OH$
$(iv)$ $A + NaHCO_3 \rightarrow C + D + H_2O$
$(v)$ $CH_3CH_2OH + E \rightarrow CH_3CH_2ONa + H_2$

Explain the following reactions with chemical equations:
$(i)$ Oxidation
$(ii)$ Hydrogenation
$(iii)$ Substitution

Give names of the following:
$(a)$ An alcohol containing $4$ carbon atoms.
$(b)$ An acid with $5$ carbon atoms.
$(c)$ Simplest ketone. Define functional group in a carbon compound. Mention names of any three functional groups with their formulae and example.

Mention four characteristics which change with increasing molecular mass in a homologous series.