Compound H is optically active and has the molecular formula C6H10 and has a five carbon ring. On catalytic hydrogenation, H is converted to I (C6H12) and I is optically inactive. Propose structures for H and I. (Draw a three-dimensional formula for each using dashes and wedges around chiral centers.)

Single replacement is a reaction in which one element reacts with another compund to form another compound and another element.

example:

A+BC > B+ AC

Double Replacement is a reaction in which the metals present in two compounds change places to form two new compounds 

example:

AB+ CD > AD+ CB (they basically switch partners)