Separation TechniquesDr. V. A. Chatpalliwar
Prof., Pharm. Chem.Head, Dept. Pharm. Chem.S. S. D. J. Coll. Pharm.Neminagar, ChandwadDist.: Nashik
Theory and Practice of Organic chemistry
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Acknowledgements
Sinhgad College of PharmacyVadgaon CampusPune
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Management & Staff
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Separation TechniquesUsed for separating• a binary mixture of organic compounds• a racemic mixture of chiral compounds
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Chromatographic Techniques
TLCPaperHPTLCHPLCGC
Capillary Electrophoresis Super-critical Fluid Chromatography UPLCPreparative HPLC
Chiral Separation
OPEC
SSE
SLE
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Binary Mixture (containing two components)
Physical means of separation
Preliminary test with solvents
Try to separate on the basis of solubility in acidic/basic solution, viz. dil./conc. HCl,
dil./conc. H2SO4, dil./conc.
NaOH/dil. NaHCO3
Re-precipitate by neutralization
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Usual Practice Consequence Only one component of the mixture
is collected in pure form/in manageable quantity
Exhaustion of sample before separating it satisfactorily due to loss is performing unwanted tests/
steps/techniques for achieving separation
Just Three Hours No Gain after lot of pain
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Salient points • Separation should be qualitative as well as quantitative;
if it is not achieved problems of contamination arise.
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
• Process used for separating the components should not induce a drastic chemical change in either component of sample
• Rational/separable mixtures should be prepared while designing the practical
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Scheme (systematic)Preliminary Examination of the mixture
States
Odour
Colour
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Polar components: solids
Pungent: AcidicFishy: BasicSweet/Agreeable/Aromatic: Neutral
Groups with free lone-pair of electrons/
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Element Detection Test (mixture)Lassaigne’s
Test
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
3 tests instead of 6
Absence of nitrogen in mixture rules out possibility of amines, amides,nitro, hydrazines, and sulphonamides
•Conservation of time
•Guides in skipping few steps of separation
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Separation
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
On the basis of physical state does not allow proper separation
chemical separation based on molecular properties allows proper separation; presence of acidic/basic functional groups should be exploited to separate the components of mixture
Toluene and Acetic acid
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Dissolution (prior to extraction) Allows dissociation of molecules from each other which otherwise are strongly held to each other by intermolecular forces
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Abolish the possibility of contamination in separated components
This dissociation helps in proper interaction between component molecules and extraction solvent
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Choice of Solvent• Should be able to dissolve wide
range of organic compounds
• Should not trigger unwanted reactions with components
• Sample/components should be recoverable after separation
• Should be immiscible with other solvent; extractable
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Diethyl ether
√
√ ethers are less reactive; next to alkanes
√ boiling point in 35 ° C
√ immiscible with water√ Far less dense (0.78 g/mL) so as to form separable bi-layers
inflammable, flash point - 45 ° C, creeping nature
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Method• All possible source
of flame/s and/or hot surfaces must be removed from the vicinity to diethyl ether.
• Fast working is required in order to avoid loss of solvent due to evaporation.
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Sample mixed with solvent
Clear solution
Partial solubility
Quantity of solvent be increased
Separation achievedFilter to obtain two separate components
Proceed for extraction
Washing the residue with the solvent assures proper separation
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Extraction (liquid-liquid)• dil. HCl/conc. HCl
• dil. NaOH/conc. NaOH
• dil. H2SO4/conc. H2SO4
• dil. NaHCO3
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Observation/inference of Lassaigne’s test
Nitrogen present
Amides
AminesHydrazines, Azo-
Nitro compounds
Sulphonamides
Nitrogen absent
aq. HCl (5%)
Carboxylic acid
Phenol
Carbonyl compounds
Alcohols
Hydrocarbons
Acyl halides
aq. NaOH (5%)
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Extraction (procedure)
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Time for interaction
aq. HCl (5%)/aq. NaOH
Two solutions
Neutralizing solvent
Neutral/acidic/basic Compound
Filter/Separate
Wash and Dry
Acidic/Basic Compound
Salt/polar compound
Evaporation
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Care to be exercisedMixing (for extraction with immiscible solvent) is advisable to be performed in beaker
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Accident-prone
Selecting proper-sized separating funnel
Extraction should be performed repeatedly for complete separation , till further neutralization (with double-strength solution) does not result in precipitation/phase separation
Small volume at interface be discarded/collected else-where
Washings should be carried till acid/base is completely removed
Drying (vacuum/desiccator/desiccant)
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
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Identification
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Acidic/Basic Compound A B
Observation/inferences from separation process
Lassaigne’s test Lassaigne’s test
Aromaticity Aromaticity
Water insoluble&
Acid/base soluble
Water insoluble&
Ether soluble
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Functional group identification and Derivative preparation
Result and Discussion
Neutral/acidic/basic Compound
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Preparation of Lassaigne’s Solution
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Fusion tube Fusion assembly Decomposing the protecting material Exposed Sodium metal
Extraction with water Filtration through soaked filter paper
Clear (not dark) Lassaigne’s solution
Addition of sample directly over exposed metal
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
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Preparation of Reagentsaq. 2, 4-Dinitrophenylhydrazine for water-insoluble carbonyl compounds
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
aq. HCl (5%) aq. NaOH (5%)
Stored Schiff’s reagent On adding sodium metabisulphite
N1V1 = N2V2
Schiff’s reagent with sample, Benzaldehyde
Schiff’s reagent with sample Benzaldehyde on proper mixing
Schiff’s reagent with p-Hydroxybenzaldehyde
Schiff’s reagent
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Preparation of Samples (examples)
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Benzoic acid and p-Aminophenol
Benzoic acid and Anthracene
Benzoic acid and m-Dinitrobenzene
Phthalic acid and Anthracene
Salicylic acid and Acetanilide
Benzoic acid and Acetanilide
α-Naphthol and Anthracene
Phthalic acid and Benzamide
Salicylic acid and Anthraquinone
α-Naphthol and Anthraquinone
p-Nitrobenzoic acid and α-Naphthol
Benzoic acid and β-Naphthol
Benzoic acid and α-Naphthol
Cinnamic acid and β-Naphthol
Salicylic acid and β-Naphthol
Salicylic acid and Resorcinol
β-Naphthol and p-Nitrophenol
Diphenylamine and Acetanilide
Diphenylamine and α-Naphthol
Urea and Toluene
Thiourea and Toluene
Benzamide and Nitrobenzene
Aniline and Nitrobenzene
p-Chlorobenzoic acid and
Diphenylamine
Salicylic acid and Urea
p-Chlorobenzoic acid and
Thiourea
p-Chlorobenzoic acid and
Aniline
Aniline and Urea
Anthranilic acid and benzamide
Combinations in red font are not be prepared as samples
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Preparation of Samples
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Should be separable by undergraduate students
Should not be prepared with quantities out-of-proportion
Should be mixed well so as to avoid easy jump to the conclusion
Should contain mono-functional compounds
Should not contain water soluble compounds
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Casual Approach be Avoided
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Samples should be prepared by technical person
Curiosity/interest of students should be respected and preserved; their memory should not be useful in the context
Enough/sufficient/rational time should be allowed for proper exercise
Compound as supplied Compound precipitated during experiment
Physical appearance of sample/compounds often mislead
Compound collected after Precipitation during experiment
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Casual Approach
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Ammoniacal Silver nitrate
Not stored due to short shelf-life
prepared just when it is needed It is never heated; gentle warming is required for reaction with some carbonyl compounds
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Risk formation of silver fulminate which explodes dangerously on drying
All apparatus in which reagent has been used should be carefully & immediately after use should be washed with dil. HNO3
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Alternatives to costly methods
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Use of Silver Nitrate
Halogen presentp-Chlorobenzoic acid
Used in Lassaigne’s test for detecting presence of any halide anion/halogen in the sample
Halogen absentBenzoic acid
Loop prepared using copper wire
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Discussion (example of Benzoic acid)The solid, white, odourless compound, melted at 119-20 °C (thermometer no. 07, calibration + 1 °
C), did not contain nitrogen, sulphur or any halogen (Lassaigne’s test) dissolved in aq. NaOH (5 %).
It decomposed sodium bicarbonate in a saturated aqueous solution to evolve carbon dioxide with
effervescence, confirming the presence of a carboxyl group. The compound was converted to an
amide derivative which melted at 127-28 °C (thermometer no. 07, calibration + 1 ° C).
The foregoing description proves the given organic compound is benzoic acid (lit. m. p. 121 ° C); its
amide derivative, benzamide, was prepared (lit. m. p. 129 ° C), both having following structures.
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
O OH O NH2
Benzoic acid Derivative: Benzamide
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Applications (apart from synthetic chemistry)• Phytochemistry
• Formulation
• Biopharmaceutical
• Forensic analysis
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Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
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AcknowledgementsMr. S. P. Wate
3/13/2012
Dr. V. A. ChatpalliwarDept. Pharm. Chem. Lecture Series
Dr. P. B. Khedekar
Dr. V. V. Parashar
Mrs. A. J. Asnani
Late (Miss) V. R. Rabra
Dr. A. A. Joharapurkar
Late Dr. R. A. Fursule
Prof. S. R. Tambe
Dr. C. D. Upasani
Mr. Pawan Porwal
Mr. Santosh S. Chhajed
All Students of M. Pharm. (Pharm. Chem.)
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