DEPARTMENT OF CHEMISTRY
GOVERNMENT DEGREE
COLLEGE-PUTTUR
SYSTAMATIC IDENTIFICATION OF UNKNOWN ORGANIC COMPOUNDS
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EXPERIMENT
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OBSERVATION
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INFERENCE
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I.
Preliminary examinations:
1)
Physical state
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Solid
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Carbohydrates,
Aromatic carboxylic acids
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Liquid
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Low
m.wt. Aldehydes, phenols, acids etc.
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2)
Colour
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Brown/red
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Phenol
(Or) Amines
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Colour
less
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Aldehydes,
Ketones, Carbohydrates, Acids etc.
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3)
Odour
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Fishy
odour
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Amines
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Phenolic
odour
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Phenols
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Almond
smell
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Aromatic
aldehydes
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Sweet
smell
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Ketones
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Strong
smell
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Low
m.wt. aldehydes, carboxylic acids
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4)
Action of heat:
The
given organic compound is taken in a test tube and heated
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Charring
taking place
Ammonia
smell is evolved
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Carbohydrates
Amides
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5)
Ignition test:
Place
of the compound in a nickel spatula and heat it gently
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Burnt
with sooty flame
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Aromatic
compound
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Burnt
with non-sooty flame
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Aliphatic
compound
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Compound
melts then chars and levels a black residue on the spatula.
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Carbohydrates
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6) Solubility
1) In
cold water
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Insoluble
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Aromatic
compounds
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Soluble
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Aliphatic
compounds
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2) In
hot water
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Soluble
and regenerated on cooling
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Aromatic
carboxylic acids/acids/phenols etc.
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3) In
dil. HCl
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Soluble
and regenerated by adding NaOH.
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Amine
is present
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Soluble
but not regenerated by adding NaOH.
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Amines
is absent
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4) In
NaOH
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Soluble
and regenerated by adding HCl.
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Acids/phenols
are present
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Soluble
but nor regenerated by adding HCl.
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Acids/phenols
are absent
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II.
DETECTION OF NITROGEN (LASSAIGNE’S TEST).
Preparation
of sodium fusion extract: Take a piece of Na metal, pressed between the
folds of the filter paper. Na piece is taken in ignition tube and heated
strongly. The bottom of the tube becomes red hot; a few drops or a pinch of
organic compound is added to the fusion tube. Then the tube is heated till
the bottom of the fusion tube becomes red hot plunge the test tube while it
is still hot in a mortar containing 5ml of distilled water and grinds the
shattered FT with a pestle and filter in to a clean TT using a fluted filter
paper and funnel. The solution should be clear and colorless if not repeat
the fusion test. The filtrate is known as sodium fusion extract, which is to
be used for detection of extra Nitrogen.
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EXPERIMENT
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OBSERVATION
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INFERENCE
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Test
for Nitrogen: Take
about 1ml of sodium fusion extract in a test tube and add a pinch of ferrous
sulphate. Heat the mixture gently until it boils. Cool for 2sec. and add 1-2
drops of con. HCl down side of the TT and shake it.
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Prussian
blue or bluish green ppt. or solution is formed.
Prussian
blue or bluish green ppt. or solution is not formed.
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Nitrogen
is present
Nitrogen
is absent
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III. IDENTIFICATION
TEST FOR FUNCTIONAL GROUPS.
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EXPERIMENT
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OBSERVATION
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INFERENCE
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Test
for carbonyl group:
Borshe’s
(2,4-DNP)test:-
To a small, amount of organic compound is taken in a TT , add few drops of
Borshe’s reagent(2,4-DNP) and dilute with water
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A
crystalline yellow or orange ppt
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Indicates
presence of carbonyl (aldehyde/ketone) group.
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Test
for Carbohydrate:
Molish
test:-Dissolve
small amount of compound in water add 3 drops of 1or α-napthal. Then add
carefully con. H2SO4 down side of the TT
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A
deep violet colouration at the junction of two rings
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It
indicates the presence of carbohydrates
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Test
for carboxylic acids:
NaHCO3
Test:-Place
a pinch or 2drops of compound in a TT and add 1ml of NaHCO3 solution
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Evolutions
of CO2 with Effervescence
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Indicates
the presentce of carboxylic acid
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Test
for Phenol:
Neutral
FeCl3 Test:-Dissolve the given compound in alcohol and add
few drops of Neutral FeCl3 solution
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Violet
or bluish green colour solution or ppt. is observed (2-naphthol don’t give
any colour)
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Indicates
the phenolic group
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Test
for amines:
Azodye
Test:-Dissolve
the given compound in a dil. HCl and cool in ice
2nd
test tube dissolve NaNO2 in water and cool it in ice
3rd
test tube dissolves 2(or) β-naphthol in NaOH Solution and cools it in Ice.
A,B
solutions are mixed fist then add C solution
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Formation
of orange red dye
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Presence
of primary amines
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Test
for Acid amides:
NaOH
test or NH3 evolution test:-Take the compound in TT and add
NaOH solution , heat the tube gently on wire guaze and smell of the gas
evolved
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NH3
gas is liberated. Formation of white dense fumes with Con. HCl.
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Presence
of amides
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Test
for alcohol:
Na
Metal test:-Take
the compound in TT and add small piece
of sodium metal
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Evolution
of H2 gas is observed
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Presence
of alcohol.
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IV.
CONFORMATION TEST FOR FUNCTIONAL GROUPS
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EXPERIMENT
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OBSERVATION
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INFERENCE
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Conformation
test for Carbonyl Group:
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Tollens test: Take a organic compound
in test tube and add small amount of tollens reagent and warm on hot water
bath
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Formation
of silver mirror
If
no silver mirror is formed
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Aldehyde
is conformed
Ketone
is conformed
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Fehling
test:
To the aqueous solution of organic compound Fehling’s A &B in added equal
proportions and heat gently on hot water bath
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A
red ppt. is formed
No
red ppt.
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Aldehyde
is conformed
Ketone
is conformed
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Conformation
Test for Carbohydrate:
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Test with con. H2SO4:
Take organic compound in dry TT and
add Con. H2SO4 drop by drop by cooling.
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The
solution turns black
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Conforms
the presence of carbohydrate
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Fehling’s
test:
To the aqueous solution of organic compound Fehling’s A &B is added in equal
proportions and heat gently on hot water bath
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A
red ppt. of CuO2 formed
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Conforms
the presence of carbohydrate.
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Tollen’s
test:
To a small amount of compound freshly prepared tollen’s reagent is added and
heated on hot water bath.
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Formation
of silver mirror on walls of the test tube
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Conforms
the presence of carbohydrate.
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Conformation
Test for carboxylic acids:
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Phenolphthalein
test:
One
drop of phenolphthalein dissolved in NaOH solution
To
given organic compound add the above solution.
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Light
pink colour solution is formed
Pink
colour disappear
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Conforms
the presence of carboxylic acid
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Ester
formation test:
Warm
few drops or pinch of compound with 1ml of ethyl alcohol and 2drops of con. H2SO4
and pour cautiously into aq. Na2CO3 solution in a small
beaker and smell
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A
pleasant smell of easter is observed
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It
conforms the presence of carboxylic acid.
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Conformation
Test for Phenol:
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Azo-Dye
Test: Dissolve
3drops of aniline in dil. HCl and cool it in ice.
2nd
test tube dissolve NaNO2 in water and cool it in ice
3rd
test tube dissolves given organic compound in NaOH Solution and cools it in
Ice.
A,B
solutions are mixed fist then add C solution
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Formation
of orange red dye
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It conforms the presence of phenol.
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Reaction
with Bromine water:
To the Phenolic compound add excess of
Bromine water
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A
white or yellowish white ppt. is formed.
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It
conforms the presence of phenol.
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Conformation
Test for amines:
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Carbyl
amine Test:
Warm 1drop or pinch of compound with few drops of CHCl3 and alc.
KOH solution in a TT and heat it.
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A
very disagreeable odour of isocyanide.
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It
conforms the presence of primary amine group
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Conformation
Test for Acid amides:
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Ester
formation test:
The
given organic compound is warmed with dil. HCl to form carboxylic acid. To
this solution few drops of Con. H2SO4 & C2H5OH
are added and heated. Pour this solution in to aq. Na2CO3
solution in a small beaker and smell.
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A
pleasant smell of easter is observed.
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It
conforms the presentce of amide
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Test
with NaNO2: To small amount of organic compound dissolved in
dil. HCl and also add little amount of solid sodium nitrate (NaNO2).
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Evolution
of N2 gas is observed.
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It
conforms the presence of amide
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Conformation
Test for alcohol:
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Test
with alkaline iodine solution: The given organic compound is warmed
with alkaline iodine solution.
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Yellow
ppt. is formed.
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It
conforms the presence of alcohol.
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Ester
formation test:
The
given organic compound is warmed with few drops of Con. H2SO4
& acetic acid and. Pour this solution in to aq. Na2CO3
solution in a small beaker and smell
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A
pleasant smell of ester is observed.
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It
conforms the presence of alcohol.
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V) DERIVATIVES FOR FUNCTIONAL
GROUPS
1.
Derivatives of Carbonyls:
Phenyl Hydrazone
Derivative:
Dissolve the organic compound in 1ml of Alcohol and add equal volume of liquid
Phenyl Hydrazine heat the contents of TT on water bath for 5mints. Cool the
solution, white Phenyl Hydrazone separated out.
2.
Derivatives of Carbohydrates:
Osazone Derivative: The given
organic compound dissolved in water adds 1.5gr of Phenyl Hydrazine Hydro
Chloride and Sodium Acetate mix well and place in hot water bath for 5mnts.
Cool the reaction mixture, Osazone derivative separated out.
3.
Derivatives of Carboxylic Acids:
Amide Derivative: Place given organic
compound in a dry TT and add Thionyl Chloride heat the contents on a hot water
bath for 17mnts. To form Acid Chloride solution.
Take 1ml of ice
cold Acid Chloride solution in a dry boiling tube, add Aniline drop by drop
with cooling stir well the contents and pour into ice water Benzoyl Derivative
separated out as a solid.
4.
Derivatives of Phenols :
Benzoyl
derivative:
Dissolve given phenol & 5% NaOH solution in a boiling tube add 2ml of Benzoyl
chloride, cork the tube and shake vigorously, the contents are poured in to ice
water Benzoyl derivative separated out as white solid.
5.
Derivatives of Amines:
N-Acetyl
Derivative:
Take 1ml of the organic compound in a clean dry test tube and add 1ml of
glacial Acetic acid and 2ml of Acetic anhydride, stir with glass road and heat
on water bath, cool and pour in to ice water, white precipitate separated out.
6.
Derivatives of Amides:
Anilide derivative:Tthe given
amide warm with Aniline, cool and pour the contents in to ice water, Anilide
separated out.
7.
Derivatives of Alcohols:
Picrate derivative: The given
Alcohol warm with Picric acid, yellow picrate is separated out.
RESULT: the given organic
compound is “--------------------------”
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