Identify the molecular formula of an alkane that exhibits only two different structural isomers.

An organic compound '$$\mathrm{A}$$' on reaction with $$\mathrm{PCl}_3$$ gives an alkyl chloride having formula $$\mathrm{C}_3 \mathrm{H}_7 \mathrm{Cl}$$. '$$\mathrm{A}$$' on oxidation with $$\mathrm{PCC}$$ forms an aldehyde having formula $$\mathrm{C}_3 \mathrm{H}_6 \mathrm{O}$$. Identify '$$\mathrm{A}$$'.

Identify tetrasaccharide from following.

What type of ligand does the ethylenediamine is?