b) Define following terms:
(i) molar magnetic susceptibility
(ii) chiral carbon
Answers
The molar magnetic susceptibility χm is defined by the product of the magnetic susceptibility χ and the molar volume Vm of a substance: χm = χ Vm = χ M / ρ. M = molar mass, ρ = density of substance.
χm is negative: In this case, the magnetic induction in the substance is reduced. The substance is called diamagnetic, χm is called diamagnetic (molar) susceptibility.
χm is positive: In this case, the magnetic induction in the substance is increased by more than the magnetic field causing the magnetization. The substance is called paramagnetic, χm is called paramagnetic (molar) susceptibility.
A chiral carbon is carbon atom attached to four different atoms or group of atoms. It is asymmetric.
Here the carbon in the centre is a chiral carbon because it is attached to 4 completely different groups.
The carbon in CH3 however cannot be a chiral carbon since it is attached with 3 hydrogen atoms that is same atom.
Also the carbon in CO2H isn't chiral. Though it is attached to different groups of atom but it is attached to only 3 group of atoms and not 4. Hence it is not considered chiral.