Exam Master Review Sheet - Purification & Analysis

CHEMCA

EXAM MASTER REVIEW SHEET

Purification & Characterization of Organic Compounds

Strategic Lab Techniques for JEE Main, Advanced & NEET

1. General Purification Methods

Sublimation

Separation of a sublimable solid from non-sublimable impurities.

Examples: Camphor, Naphthalene, Anthracene, Benzoic Acid.

Crystallization

Based on difference in solubility of compound and impurity in a suitable solvent.

*Impurity should be either insoluble or highly soluble.*

2. Distillation Techniques

Method	Principle / Criteria	Common Examples
Simple Distillation	Difference in B.P. is large (> 25 K). Liquids are stable at B.P.	Chloroform (334K) & Aniline (457K)
Fractional Distillation	Difference in B.P. is small (< 25 K). Uses a fractionating column.	Acetone & Methyl Alcohol; Crude Oil fractions
Vacuum Distillation	Liquids that decompose at or below their normal B.P. (Reduced pressure).	Glycerol from spent-lye; Conc. of Sugar juice
Steam Distillation	Steam-volatile and immiscible with water. \(P_{total} = P_{water} + P_{org}\).	Aniline; o-nitrophenol; Essential Oils

3. Chromatography

Adsorption Chromatography

Based on differential adsorption on an adsorbent (Silica/Alumina).

Types: Column & Thin Layer (TLC)

Partition Chromatography

Based on continuous differential partitioning of components between phases.

Example: Paper Chromatography

Retardation Factor (\(R_f\)): \[ R_f = \frac{\text{Distance moved by the substance from baseline}}{\text{Distance moved by the solvent from baseline}} \]

*Values of \(R_f\) are always less than 1.*

4. Qualitative Analysis (Detection)

Lassaigne's Extract: Fusion of organic compound with Sodium metal to convert covalent bonds to ionic bonds (\(NaCN, Na_2S, NaX\)).

Element	Reagents Added	Observation / Complex
Nitrogen (\(N\))	\(FeSO_4\) + \(H_2SO_4\)	Prussian Blue [\(Fe_4[Fe(CN)_6]_3\)]
Sulfur (\(S\))	Sodium Nitroprusside	Violet color [\(Na_4[Fe(CN)_5NOS]\)]
N + S	\(FeCl_3\)	Blood Red color [\(Fe(SCN)_3\)]
Halogens (\(X\))	\(AgNO_3\) + \(HNO_3\)	\(Cl\): White, \(Br\): Pale Yellow, \(I\): Yellow ppt

5. Quantitative Analysis Master Formulas

Carbon & Hydrogen

\[ \%C = \frac{12}{44} \times \frac{\text{mass of } CO_2}{\text{mass of compound}} \times 100 \]

\[ \%H = \frac{2}{18} \times \frac{\text{mass of } H_2O}{\text{mass of compound}} \times 100 \]

Carius Method (Halogens)

\[ \%X = \frac{\text{At. mass of X}}{\text{Mol. mass of } AgX} \times \frac{m_{AgX}}{m_{comp}} \times 100 \]

Nitrogen Estimation

Duma's Method:

\[ \%N = \frac{28}{22400} \times \frac{V_{STP}}{m_{comp}} \times 100 \]

Kjeldahl's Method:

\[ \%N = \frac{1.4 \times N \times V}{m_{comp}} \]

*Not applicable for Nitro, Azo, or Ring Nitrogen (Pyridine).*

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