Download PRACTICAL ORGANIC CHEMISTRY

Jazan University
Faculty of Science
Chemistry Department
PRACTICAL
ORGANIC CHEMISTRY
3rd Year Students
Part I
Name:………………..…………………………
Group:……………....…………………………
Ac. Year:……….…..………………………….
INVESTIGATION
OF SIMPLE ORGANIC COMPOUNDS
A – PHYSICAL PROPERTIES:
A knowledge as to whether a given compound is liquid or solid (if
solid, then crystalline or amorphous) is of great help in its identification
(this can by consulting tables of known compounds).
I-1- Colour:
The colour of the original sample is noted. Some compound show
colour due to impurities, which is frequently produced as a results of their
slow oxidation by moist air (freshly distilled aniline is nearly colourless but
goes reddish brown when kept for a longer time), while many others show
colour due to the presence of chromophoric groups in them. A brief
summery of conclusions that can be drawn by the observation of colour is
given here.
Observation
Orange-red
Brown
Pink
Greenish-yellow
Yellow
Inference
Nitoanilines, azo compound, βnaphthoquinone, alizarin
Higher aromatic amines, diamines
Naphthols
p- nitroso compounds, quinhydrone
Iodoform, nitrocompounds, quinines, αdiketones
Colourless, turning reddish
Phenol, aniline, aminophenols, tannic
brown or pinkish (due to air
acid, α- and β- aphthylamines
oxidation)
Colourless, turning yellowish or Anthracene, cinnamic acid, cresols,
yellow-brown
…etc
Carbohydrates, aldehydes, ketones,
Colourless
acids, esters, alcohols, ethers, many
hydrocarbons
‐ 2 - I-2- Odour :
Many types of organic compounds have characteristic odour and so
the ability to detect and remember an odour is helpful in qualitative
analysis. Some of the odour characteristics of compounds are given here.
Observation
Odour of better almond
Mouse-like
Cinnamon-like
Pleasant-fruity
Pleasant, sweet
Garlic
Phenolic (carbolic)
Pungent, irritating
Camphor-like
Intensely disagreeable
Vingar-like
Cucumber-like
Pyridine-like
Fish-like
odourless
Inference
Benzaldehyde, benzonitrile,
nitrobenzene
Acetamide, acetonitrile
Cinnamic acid
Ester
Chloroform, diphenylamine, alcohols
Thiophenols, thioalcohols
Many phenols
Lower acids, lower aldehydes, acid
halides, thioacids
Pinacol, hexachloroethane
Isocyanides
Acetic acid, aspirin
Chloral
Heterocyclic bases
Lower aliphatic amines, side-chain
aromatic amines
Carbohydrates, aromatic acid, glycerol,
solid aliphatic acid, …etc.
B- CHEMICAL PROPERTIES:
II-1- Elements Test (Lassaigne,s Test)
a) Required chemicals:
Soda limes, sodium metal (Na), distilled water, ammonium oxalate,
ammonium tartarate, acetanilide, benzamide, acetamide, antharnilic acid,
‐ 3 - glucose, fructose, sulfanilic acid, aniline HC1, aniline H2SO4, lead acetate,
ferrous sulfate, sulfuric acid, sodium nitroprusside and silver nitrate.
b) Apparatus:
Beakers, conical flasks, glass rod, ignition tubes, Bunsen flame, filter
papers, funnels, test tubes, rack for test tubes and litmus papers.
c) Experimental tests:
This test is aimed to identify the nitrogen, sulphur and halogen in
organic compounds and it can be carried out by fusion of the organic
substance with sodium metal in the presence of excess soda lime
(NaOH/CaO). The following equations express the reaction of element
after reacted with sodium:Na + C + N →NaCN (nitrogen compounds)
2 Na + S → Na2S (sulfur compounds)
Na + X → NaX (halogen compounds, X = Cl, Br, ..)
Method:
1- A small portion of the finely powdered substance is mixed with a
small amount of powdered soda lime and the mixture is then rolled
within a small flattered piece of clean sodium metal.
2- The roll is introduced into a dry micro ignition tube and covered
with an amount of soda lime.
3- Heat the tube gently, near the outer post of the flame. When any
reaction sets in, remove the tube from the flame and wait till the
reaction subsides.
4- Heating of the ignition tube is continued gently until no more
reaction occurs.
5- Heating is then continued more strongly until the lower part of the
tube becomes red, then plunge the hot tube at once, into a beaker
containing about 10 ml of distilled water.
6- Crush the tube well, boil the contents of the beaker and break any
lumps present, then filter.
‐ 4 - 7- The N, S and halogen should be detected in the alkaline filtrate
according to the following tests.
II-1-1- Test for Nitrogen:To carry out this experiment in a clean test tubes take about 1 ml of
the filtrate and 1 ml of FeSO4 solution followed by addition of one-two
drops only of concentrated H2SO4 the color of the solution turns to green or
blue indicted of the presence of nitrogen. If no nitrogen in the compound
the color will not change.
Equations:
Na + C + N → NaCN
FeSO4 + 2 NaOH→ Fe(OH)2 + Na2SO4
Fe(OH)2 + 6 NaCN → Na4[Fe(CN)6] + 2 NaOH
Sodium ferrocyanide
Na4 [Fe(CN)6] + Fe2 (SO4)3→ Fe4 [Fe(CN)6]3
Ferric-ferrocyanide (Prussian blue)
II-1- 2- Test for Sulfur:i) Sodium nitroprusside test.
In a clean test tube take about 1ml of filtrate then add about 1ml of
sodium nitroprusside the color changes to purple in case of the presence of
sulphur.
2 Na + S → Na2S
Na2S + Na2 [Fe(CN)5NO] → Na4 [Fe(CN)5] NOS
ii) Lead sulfide test.
In a clean test tube take about 1ml of the filtrate then add few drops
of acetic acid followed by 3 drops lead acetate, then shake the tube, the
black precipitate of lead sulfide indicates the presence of sulfur.
CH COOH
3
 PbS + 2 CH3COONa
Na2S + (CH3COO)2Pb  
‐ 5 - II-1-3- Test for Halogen:i) In the presence of (Nitrogen or Sulfur).
In a test tube take about 1ml of the filtrate then add about 1 ml of
conc. HNO3 then boil the mixture for few minutes. Cool the solution and
then add about 0.5 ml of silver nitrate (AgNO3) solution: White precipitate formed in case of chlorine (Cl).
 Pale yellow precipitate formed in case of bromine (Br).
 Yellow precipitate formed in case of iodine (I).
ii) In the absence of (Nitrogen and Sulfur)
In a test tube, take about 1 ml of the filtrate then added about 1-2 ml
of dilute HNO3 followed by the addition of about 1 ml of AgNO3 solution
and observe the results as described above.
Equations:Na + X → NaX
NaX + HNO3 + AgNO3 → AgX + NaNO3
Where: X = Cl, Br, I
The results should be written as:
No
N
S
X
II-2- Action of Heat (Ignition Test):
Place a little of the substance (0.1g) on a piece of porcelain and then
heat it over a low flame, raising the temperature gradually. Observe
whether the compound is volatile; inflammable (if so, nature of the flame);
or melts, decomposes or a residue is left. If a residue is left, it is cooled and
drop of distilled H2O is added to the residue and tested with litmus paper
‐ 6 - (or ph.ph. indicator). Then a little of dil. HCl is added to see whether any
gas is evolved or not.
Observation
a) Burn with a smoky flame
b) Burn with a non-smoky flame
c) Melts, darkness, swells and then
chars with odour of burnt sugar.
d) Chars without melting with the
odour of burnt sugar
e) Residual ash
Inference
Aromatic compounds, or
chorolhydrates
Aliphatic compounds
Sugar
Starch, inulin, tartaric, citric, or their
salts, lactate
Organo metallic compounds or
metallic salts of acids
II-3- Heating with Soda-Lime:
Mix well the compound (0.g) with powdered soda-lime (1g) in a dry
test tube, cover with a layer of soda-lime and heat first gently and then
strongly, notice any odour or change in colour.
Observation
Inference
Ammonium salts of amides, imides,
a) Ammonia or ammonical vapours
nitriles, aliphatic amino acids or poly
evolved
nitro-compounds.
b) Chloroform produced (gives a
Chloral hydrates
characteristic odour while cold)
Carbohydrates or some aliphatic
c) Odour of burnt sugar
hydroxyl acid and their salts
Phenolic acids or phenyl esters of
d) Phenolic odour
carboxylic acids
e) Benzene produced
Benzene carboxylic acid or their salts
Amine salts, anilinides or aromatic
f) Odour of aromatic amine
amino-carboxylic acids
g) Colour changes yellow to brown
Many aromatic nitro compounds
and then black
‐ 7 - Ammonia odour
RCOONH4 +
NaOH / CaO
RCOONa + NH3 + H2O
RCOONH2 +
NaOH / CaO
RCOONa + NH3
NaOH / CaO
RCOONa + NH3
RCO
RCO
+
NH
Benzene odour
COOH
+
NaOH / CaO
+
Na2CO3
+
NaOH / CaO
+
NaCl + H2O
Aniline odour
NH3Cl
NH2
NH2
+
NaOH / CaO
+
Na2CO3
+
NaOH / CaO
+
RCOONa
COOH
NHCOR
Phenolic odour
OH
OH
COONa
+ NaOH / CaO
+
Na2CO3
Chloroform odour
CCl3CHO.H2O
+ NaOH / CaO
CHCCl3
+ HCOONa
‐ 8 - II-4- Treatment with 20% NaOH solutions:
Add about 5 ml of 20% NaOH solution to the compound (0.1g).
Note the reaction while cold and then warm or heat if necessary.
Observation
Inference
a) Dissolves on cold (warm) but
not soluble in water
Some aromatic acid or water
insoluble phenols.
b) Colour deepens on standing
Some polyhydric phenols,
aminophenone or benzoquinone
c) Ammonia evolves on cold
Mostly ammonium salts of acids
d) Chloroform produced as oil
Chloral or its hydrates
e) Oil or ppt. formed
Salts of aliphatic or aromatic amines
f) Yellow to brown resin on
heating
Carbohydrates (sucrose and
starchgive only a faintly yellow
coloured product) or aliphatic
aldehydes (except HCHO)
g) Ammonia evolves on heating
Amides, imides, nitriles or urea.
h) Oil or ppt. is formed on heating
Anilides.
‐ 9 - II-5- Treatment with conc. H2SO4 acid:
To a small quantity (0.1g) of the substances contained in a dry test
tube, add about 1ml of conc. H2SO4 acid and note the reaction first while
the mixture is cold and then after it has been gently warmed.
Observation
Inference
a) Evolution of CO and CO2
without charring but the mixture
turns yellow.
Citric acid and its salts.
b) rapid charring with
effervescence ( evolution of CO
and/or CO2 and SO2)
Carbohydrates, tartarates, lactates.
c) evolution of CO and CO2 but no
blackening
Oxalates
d) evolution of pungent vapour but
no blackening and no marked
effervescence
Many simple carboxylic acids and
their salts
e) blackening without
effervescence
Phenols.
CH2COOH
HO C COOH
CH2COOH
H2SO4
CH2COOH
C O
CH2COOH
+
CO
+ CO2 +
H2O
Acetone dicarboxylic acid
HO CHCOOH
HO CHCOOH
H2SO4
CH3COCOOH
+ CO2
+
H2O
Pyruvic acid
COOH
COOH
H2SO4
CO2
+
CO2
+
H2O
‐ 10 - II-6- Nitration test:
Boil a portion of the solid with a mixture of equal volumes of conc.
HNO3 and H2SO4 acid in a dry test tube. When the brown fumes cease to
evolved. Pour the contents into a beaker containing about 30ml of water.
Nitration of liquid
Great care must be taken during nitration of liquids. Alcohol under
any conditions are not to be nitrated. Liquid in general, react more
vigorously and nitrated more easily than solids.
Procedures:
To one drop of the liquid add continuously one drop of conc. Nitric
acid and if necessary heat gently, then add another drop of acid, warm and
finally add 1 ml of conc. sulphuric acid, then proceed as usual.
Notes on nitration:
1. some aromatic compound are not nitrated under the above
experimental conditions (e.g. polyhydroxy compound: resorcinol,
gallic acid).
2. Other aromatic compound give rise to almost colourless nitrocompounds which are not precipitated in the nitration medium (e.g.
some substituted and polycarboxylic benzoic acid, phthalic acid.
3. Some aliphatic compound (specislly some salt of aliphatic acids),
when subject to the nitration test give an indication of an unture
aromatic nature, e.g. iron and cobalt salts, when nitrated give
coloured solution (due to their cations) and lead and barium salts
give, on nitration white ppt. of the insoluble sulphates. In this latter
case reference is made to reaction π-2 (metallic residue).
Observation
Inference
a) a yellow , orange or red coloured
Aromatic compound
solution, oil or ppt.
b) –ve
Aliphatic compound
‐ 11 - II-7- Acidity test:
A cold solution of NaHCO3 is added to a cold solution of the
substance in H2O or alcohol or even to a suspension in H2O.
Observation
Inference
a) Effervescence with evolution of
CO2
A carboxylic acid, aniline salts, urea
salts sulphonic acid or phenolic
compounds activated by nitro groups.
b) –ve
Non acidic compound
RCOOH
+
RCOONa
NaHCO3
SO3H
CO2 + H2O
+
SO3Na
NaHCO3
+
+
NH2
CO2
+
H2O
NH2
NH3Cl
NH2
+ CO2 +
NaHCO3
+
NaCl
OH
OH
NO2
H2O +
NO2
NO2
+
+
NaHCO3
CO2 +
H2O
NO2
NO2
NH2CONH3NO3
NO2
+
NH2CONH2 + CO2 + H2O +
NaHCO3
NaNO3
‐ 12 - II-8- Solubility and Reverse precipitation :
Observation
Inference
a) Soluble in 5% Na2CO3 soln. and reprecipitated
dil. HCl acid and not soluble in H2O.
by
Aromatic
carboxylic acid
b) Soluble in 5% NaOH soln. (but insoluble in Na2CO3
soln. and H2O) and reprecipitated by dil. HCl acid.
Water-insoluble
phenol
c) Soluble in dil. HCl ( not soluble in H2O) and
reprecipitated by NaOH solution.
Organic base
COOH
+
HCl
Na2CO3
Insoluble
ONa
OH
+
soluble
NH2
Insoluble
OH
HCl
NaOH
Insoluble
Insoluble
NH2
NH3Cl
+
NaCl
+
soluble
Insoluble
R
COOH
COONa
NaOH
HCl
R
R
soluble
Insoluble
‐ 13 - II-9- Acidity test:
Procedure:
To obtain a neutral FeCl3 soln., add a few drops of NH4OH soln. to
FeCl3 soln. till a permanent ppt. is formed and filter. Add a few drops of
this FeCl3 soln. to dilute soln. of the substance in water or in alcohol or
(neutral soln. in case of acids).
Observation
Inference
a) Intense purple, blue or red colour.
Phenol, phenolic acids, esters
and amides
b) Buff ppt. (cleared by dil. HCl but
replaced by a white ppt. of free acid.
Aromatic acid and succinate.
c) Greenish colour of ppt.
Catechol, qunol or βnaphthol.
d) Red colour (discharges on addition of
dil. HCl )
Amino acids, formic or acetic
acids.
e) Greenish colour ( the substance in dil.
HCl )
Some amines
‐ 14 - REACTION OF CHARACTERISTIC GROUPS
III-Characteristic group having no additional elements:
Characteristic groups considered in this section contain C and H
(with or without O) elements.
III-1-Carbohydrates:
All the compounds of this class given for identification are solids and
are covered under the classes given below:
I-1-a-Monosacharides (glucose, galactose and fructose).
I-1-b-Disacharides (maltose, lactose and sucrose).
I-1-c-Polysaccharides (starch and inulin).
Glucose
Galactose
Fructose
Sucrose
Maltose
Lactose
‐ 15 - Physical properties:
Colourless solids, which decomposes on heating and therefore have
no definite melting points. All except starch and inulin are soluble in water.
III-1-1-Molish's tes (characteristic test for carbohydrates):
Place 0.025g of the substance in a test-tube containing 2.5ml of H2O
and mix it with 2 drops of a 10% solution of 1-naphthol in ethanol. Allow 1
ml of conc. H2SO4 acid to follow down the side of the test tube (the acid
forms a heavy layer at the bottom) and allow to solution to stand for a
minute. If a carbohydrate is present a red-violet ring appears at the interface
of the two liquids : the colour quickly changes on standing or shaking, a
violet solution being formed. Shake and allow the mixture to stand for 2
minutes, then dilute with 5ml of H2O. In the presence of a carbohydrate, a
violet precipitate will appear immediately.
Glucose
Hydroxyl methyl furfural
Identification of sugars:
III-1-2-Reduction:
a) Barfoed's reagent:(Cu acetate in acetic acid)
Heat a test-tube containing 1ml of the Barfoed's reagent and 1ml of a
dilute solution of the carbohydrate in a boiling water bath.
Observation
Inference
Red Cu2O ppt. within 2 minutes
Monosaccharides
Red ppt. after 5 minutes boiling
Disaccharides
No red ppt.
polysaccharide
Glucose
Gluconic acid
‐ 16 - b) Fehling's solution:
(Fehling 1 : CuSO4. H2O and Fehling 2 : sod. Tartarate in NaOH soln.)
Place 3 ml of Fehling's solution(prepared by mixing equal volumes
of Fehling's solution of 0.1g of the carbohydrate in 2 ml of H2O and
continue the boiling for 1-2 minutes.
Fehling reagent
Observation
Inference
A yellow-red Cu2O ppt.
Reducing sugar
No red ppt.
Non reducing sugar (sucrose)
Ketose
Enediol
Aldose
c) Bendict's solution:
This is a modification of Fehling's solution. To 3 ml of Bendict's
solution, add 2 ml of dil. soln. of carbohydrate, boil for 2 minutes and
allow to cool.
Observation
Inference
A red Cu2O ppt.
Reducing sugar
Clear solution
Non reducing sugar
‐ 17 - Bendict reagent
d) Tollen's reagent ( Ammonical silver nitrate)
Add 1 ml of Tollen reagent to 1ml of carbohydrate soln. and heat
gently.
Observation
Inference
A silver mirror or black ppt. on cold or
after gentle heating
Monosaccharide.
A silver mirror on heating.
Lactose or maltose.
-ve.
Sucrose.
Glucose
+
(Ag(NH3)2)OH
→
Gluconic acid
+
Ag↓
III-1-3-Osazoneformation:
Carbohydrates react with phenylhydrazine to give crystalline
compounds known as osazone. Such compounds are used to identify the
different types of carbohydrates by observing the crystallineform of the
osazone under the microscope.
Dissolve 0.2 g of the carbohydrate, 0.4g of phenylhydrazine
hydrochloride and 0.6g of sod. acetate in 4 ml of water and dip the tube in a
beaker containing boiling water and leave it as such for 20 minutes then
place it a side to cool slowly. The osazone separates as a yellow crystalline
precipitate.
‐ 18 - Glucose or Fructose
+
PhNHNH2
HC
NNHPh
C
NNHPh
Osazone derivatives
Glucosazone or Fructosazone
‐ 19 - III-1-4-Rapid furfural test:
Add 1 ml of alc. 1-naphthol solution to 1 ml of the carbohydrate
solution and then add 6-8 ml conc. HCl acid and heat to boiling.
Observation
Inference
Violet colour (immediately).
Fructose or Sucrose
Violet colour (after a while).
Glucose, Maltose or Lactose
-ve.
Galactose.
III-1-5-Test for Fructose:
Upon heating a little fructose with dilute CoCl2 solution, cooling and
treat with a little ammonia solution.
Observation
Inference
A violet purple colour, gradually fading.
Fructose.
Green Co(OH)2 ppt.
All other carbohydrates.
Identification of polysaccharide:
Starch
Starch occurs in plant tissues in the form of small white granules. It
is insoluble in water but it absorbs about 35% of a weight when subjected
to moist air.
III-1-6-Action of Iodine:
Starch may be identified by the blue colour with iodine ions. The
formed compound is easily decomposed and its colour is discharged on
heating and is restored on cooling.
III-1-7-Hydrolysis:
When starch is heated with dil. Acids, the so called soluble starch is
formed which gives on further heating gum-like materials known as
dextrin. The final hydrolysis products are maltose and glucose.
‐ 20 - Prepare a paste from starch and little water. Add to part of this 1/2 ml
of dil. Sulphuric acid and heat gently for 5 minutes. Test this solution every
now and then by taking one drop with a glass rod and adding it to iodine
solution. When no colour is produced, it shows that hydrolysis of starch to
glucose is complete.
III-2-Carboxylic acids:
All acids give a positive acidity test as they contain a carboxylic
group. They react with NaHCO3 or Na2CO3 to give the sodium salt of acid
with evolution of CO2 gas. The occurrence of effervescence denotes the
presence of a free carboxylic group.
III-2-1-Acidity test( characteristic test for acid):
Add 1 ml of NaHCO3 solution to 1 ml of an aqueous or alc. Solution
of compound (unknown). Effervescence take place due to the evolution of
CO2 gas.
RCOOH
+
NaHCO3
→
RCOONa
+
CO2↑
+ H2O
III-2-2-Ester formation test:
To 0.5 g of the compound, add abs. ethanol (1ml), a few drops of
conc H2SO4 and heat the content, in a dry test tube, gently for 1 minute.
Note the fruity smell of the resulted ester.
RCOOH
+
C2H5OH
→
RCOOC2H5
+
H2O
III-2-3-Iodate-iodine test:
Take 4-5 drops of an aqueous or alc. soln. of the compound in a test
tube, add 2 ml of 2% KI solution and 2 ml of 4% KIO3 soln. into it and
keep the test tube in a boiling water bath for 1-2 minutes, then cool and add
3-4 drops of starch solution. A blue or violet colour indicates the presence
of COOH group.
5KI
+
KIO3
+ 6 RCOOH → 3I2
+
3H2O
+ 6 RCOOK
‐ 21 - Identification of acids
Acids may be aliphatic or aromatic.
A) For aliphatic acids:
Malonic acid
Fumaric acid
Oxalic acid
Maleic acid
Tartaric acid
Succinic acid
Citric acid
III-2-4- Effect of heat on solid:
Odour of acetic acid. (Solution of solid in acetic anhydride
→yellowish red solution with green fluorescence)
Malonic acid
III-2-5- Neutral solution + neutral FeCl3:
Observation
Inference
Red colour turn brown
ppt. by boiling.
Maleic acid ( unsaturation test +ve , fluorescein
test, red colour).
Red brown ppt.
Fumaric ( unsaturation test +ve , fluorescein
test, red colour).
Buff ppt.
Succinic acid (fluorescein test green)
Yellow colour
Oxalic , tartaric or citric acid
‐ 22 - Notes:
1-Neutral solution of an acid:
Add ammonia solution in excess to a small amount of the solid acid
or its solution. Heat until no more ammonia gas evolved. The residual is the
neutral solution.
2- fluorescein test:
In a clean dry test tube, fuse carefully together, few crystals of
resorcinol and an equal quantity of the solid acid, or its anhydride
moistened with 2 drops of conc. H2SO4. Pour into excess NaOH.
HO
HO
OH
OH
HO
O
OH
+
H
H
conc. H2SO4
C
O
O
C
C
O
O
C
OH
O
O
H
O
O
C
COO
Green f luorrescence
‐ 23 - III-2-6- Neutral solution + neutral CaCl2:
Observation
Inference
White ppt. immediately on cold insoluble in
acetic acid.
Oxalic acid
White ppt. after scratching and warming,
soluble in acetic acid.
Tartaric acid (Fenton's test)
White ppt. after boiling, insoluble in acetic
acid
Citric acid (Deng's test)
Deng's test:
Add 1 ml of Deng's No. 1 to 3 ml of neutral citric acid and heat to
boiling. Add 2 drops of Deng's No. 2 and note that the colour of pot.
permanganate is discharged. (redox reaction).
Fenton's test:
Add 1 drop of FeSO4 soln. to 2 ml of tartaric acid soln. then add
dropwise H2O2 soln. till the solution acquires a green colouration. Add
excess of NaOH soln. a violet colour is produced. (redox reaction).
B) For Aromatic Acids:
Salicylic acid
Phthalic acid
Phenylacetic acid
Cinnamic acid
Benzoic acid
‐ 24 - III-2-7-Neutral solution + neutral FeCl3:
Observation
Inference
Violet colour.
Salicylic acid
Buff ppt.
Phthalic , Cinnamic, Phenylacetic or Benzoic acid
Amm. Benzoate
Ferric benzoate
Basic Ferric benzoate
To differentiate :
III-2-8-Phthalein test:
In a clean dry test tube, fuse carefully together, few crystals of the
acid and 2 drops of phenol, moistened with 2 drops of conc. H2SO4. Pour
into excess NaOH, if red colour, then phthalic acid.
OH
HO
HO
OH
+
H
H
conc. H2SO4
C
O
O
C
C
O
O
C
OH
O
H
O
O
C
COO
Red Colour
‐ 25 - III-2-9-Fluorescein test:
+ve
phthalic acid
III-2-10-Unsaturation test:
If the solution of the substance is sod. carbonate discharge the colour
of bromine water and also a few drops of dilute KMnO4. If +ve, then
cinnammic acid
III-2-11-Boiling with test:
If oily drops are formed, then phenyl acetic acid. If all the above tests
(phthalein, fluorescein, unsaturation and boiling with water) are negative,
then Benzoic acid.
III-3-Hydroxyl compounds (phenol and alcohols):
The test for –OH group may be accomplished in any one of the
following methods, provided that –COOH group is absent.
III-3-1-Acetyl chloride test:
A portion of the substance (solid or liquid) is added to 1 ml of
CH3COCl, in a dry test tube, a vigorous evolution of HCl gas indicates the
presence of –OH group.
III-3-2-Benzoyl chloride test:
Benzoyl chloride may be used instead of CH3COCl, but warming is
necessary in this case.
‐ 26 - III-3-3-FeCl3 Test:
Hydroxyl group of phenols and enolic compound gives colour
(usually violet) with FeCl3. This test is valid in presence of carboxylic
group.
Add few drops of neutral FeCl3 solution to a solution of the
substance in water or in alcohol (note the colour produced).
HO
OH +
O
FeCl3
O
Benzoquinone
OH HO
OH
2
+
FeCl3
2-Dinaphthol
OH
HO
2
+
OH
FeCl3
III-3-4-Sodium metal Test:
Clean pieces of sodium are added to small amount of dry ether or
benzene until evolution of H2 ceases if present. Then add a little of the
substance, if bubbles of H2 gas evolve, -OH group is present.
Identification of Phenols:
‐ 27 - Water soluble phenols
Catechol
Resorcinol
Quinol
Pyrogallol
Aq. or alc. soln. of phenol + Neutral FeCl3
Observation
Inference
Violet discharged by HCl.
phenol
Violet discharged by AcONa.
Resorcinol
Green turns red by NaOH.
Catechol
Green crystals
Hydroquinone
Red-turns violet by NaOH.
Pyrogallol.
Greenish turns to violet
α-Naphthol.
Faint green
β-Naphthol.
III-3-5-Liebermann-nitroso reaction:
Phenol react with nitrous acid to give p-nitrosophenols which
condense with excess phenol to give indophenols (usually red). When
solution of the latter is rendered alkaline, a blue or green anion is liberated.
To a small amount of NaNO2 in a clean dry test tube, add 0.5g of
phenol and heat gently for 1 min., cool, add 1 ml of conc. H2SO4 with
shaking. A deep green or blue colouration develops (sometimes only after
1-2 min.). Dilute cautiously, the solution, turns red. Now add an excess of
NaOH soln., the green or blue colouration reappears.
‐ 28 - Phenol
H2SO4
Dilution
NaOH
phenol
Green or blue
Red
Green or blue
α-Naphthol.
Green
Ill-defined
Ill-defined
β-Naphthol.
Brownish back
Ill-defined
Ill-defined
Catechol
Deep green
Dirty brown
Red
Resorcinol
Deep blue
red
brown
+
HO
HO
HONO
NO
C6H5OH
N
NaO
O
NaOH
N
HO
O
III-3-6-Chloroform and NaOH (Reimer-Timann reaction):
Dissolve the phenol in conc. NaOH (20%), add 1-2 ml of chloroform
and heat gently. Notice the colouration produced.
Phenolic comp.
colour
Phenolic comp.
colour
phenol
No-colour
Catechol
Green
α-Naphthol.
Deep blue fading
to green
Deep blue fading
to green
Resorcinol
Red with
fluorecence
-ve
β-Naphthol
Phenol
quinol
Salicylaldehyde
‐ 29 - III-4-Metallic salts of acids:
III-4-1-Test for metallic residue (Action of heat):
Heat a small portion of the substance on a piece of porcelain, leaves
a residue, when dissolved in dil. HCl, CO2 evolves with effervescence. In
this case a metallic salt of acid is present.
a) White residue; Alkali metal in the form of carbonate or alkaline
earth metal left as oxide.
b) Red or yellow residue, lead oxide.
c) Yellow residue when hot and white when cold, zinc oxide.
d) Black residue, CuO, Co2O3, Fe2O3.
The metallic residue can be further identified by dissolving it in dil.
HCl acid and searching for the basic radical in the usual way.
III-4-2-Nitration test:
-ve
salt of aliphatic acid
+ve
salt of aromatic acid
Identification of salt of an aliphatic acid:
III-4-3- Treatment with FeCl3:
i) Red colour turns to brown by boiling.
Formate : Reduces amm. AgNO3.
Acetate : Esterify to ethylacetate.
HCOONH4 + FeCl3
HCOO
3
Fe
HCOOFe(OH)2
Basic ferric formate
ii) Carry out iodoform test, if +ve then lactate.
iii) Follow then the same steps as in the case of free aliphatic acids.
Identification of salt of an aromatic acid:
Follow the same steps as in the case of free aromatic acids
‐ 30 - III-5-Aldehydes:
III-5-1-Schieff's reagent:
Add 2-3 drops (if the substance is a liquid) or 0.1 gm of the solid to 2
ml of Schiff's reagent. A pink colour developes within 2 minutes. (Schiff's
reagent must not be warmed, nor alcohol must be used as a solvent).
Note :
1. Schiff's reagent (rosaniline hydrochloride (magenta) is dissolved
in water (deep-red solution) and SO2 is passed in until the
magenta colour is discharged.
2. The reaction of aldehydes with Schiff's reagent is not very
characteristic due to the reducing properties of the aldehydes.
Schiff reagent
III-5-2-Tollen's reagent:
Aldehydes reduce Tollen's reagent (ammonical AgNO3 soln.) to
metallic Ag.
Place 1 ml of Tollen's reagent in a clean test tube, then add a small
portion of the aldehyde. Warm the reaction mixture and notice the
formation of a silver mirror (or ppt.) on the inner wall of the tube.
III-5-3-Fehling's solution:
Aldehydes reduce Fehling's soln. to a red cuprous oxide.
R-CHO
+ Cu2
RCOOH
+
Cu
‐ 31 - Mix together two equal volumes of Fehling 1 and Fehling 2. Heat the
mixture then add 1 ml of the aldehyde and reheat gently. Note the
formation of a yellow-red ppt. of Cu2O.
N.B. Reaction with Tollen's reagent and Fehling's solution is characteristic
only for aldehydes.
III-6-Ketones:
In the absence of aldehydes, ketones may be detected by formation
of derivatives such as oxime, phenylhydrazone or 2,4dinitrophenylhydrazone.
III-6-1-Formation of 2,4-dinitrophenylhydrazone:
For detection, add 0.05-0.1 g of the substance to be tested to 3 ml of
the 2.4-dinitrophenylhydrazine reagent, and shake. If no precipitate forms
immediately allow to stand for 5-10 minutes. A crystalline precipitate
indicates the presence of carbonyl compound. Occasionally the precipitate
is oily at first, but this becomes crystalline upon standing.
‐ 32 - Identification of ketones:
Acetophenone
Benzophenone
O
O
O
O
p-Benzoquinone
Anthraquinone
III-6-2-Boiling with water:
Observation
Inference
Oily drops
benzphenone
No oily drops
p-benzoquinone or anthraquinone
III-6-3-Tollen's reagent:
Add 1 ml of Tollen's reagent to a few drops of cold aqueous solution
of ketone, give only, black ppt. or silver mirror with p-Benzoquinone.
III-6-4-Confirmatory tests:
For p-benzoquinone
a) Dissolve 0.2 g of benzoquinone in 1 ml of alcohol, add 2 drops of
aniline and warm gently, a reddish ppt. of quinine-dianiline is
formed.
Quinonedianiline
‐ 33 - b) Reduction (to quinol):
Add aq. benzoquinone solution to KI solution acidified with few
drops of H2SO4, I2 is librates (test by starch).
For anthaquinone:
III-6-5-Reduction with Zn dust:
Heat 0.2 g of anthraquinone with about 5 ml of NaOH solution add a
small amount of Zn dust, a red colouration is produced. When all Zn dust
has dissolved, the solution is slowly decolouration on shaking (due to
atmospheric oxidation).
Oxanthranol
III-7-Hydrocarbons
Naphthalene
Anthracene
Many hydrocarbon form molecular compound with picric acid, for
example, naphthalene picrate C10H8-C6H2(NO2)3OH.
III-7-1-Picrate test:
Dissolve 0.1 g of the hydrocarbon and 0.2 g of picric acid separately
in the minimum volume of benzene (about 2 ml), mix the two solutions and
allow to cool. Filter and wash with 2 ml of ethanol.
‐ 34 - Observation
Inference
Yellow crystals
Naphthalene (150 ºC)
Red crystals
Anthracene (138 ºC)
III-7-2-Nitation test:
Nitric acid reacts with naphthalene, in the presence of glacial acetic
acid to give a nitronaphthalene while anthracene is not readily nitrated with
nitric acid.
Dissolve by heating, 0.5 g of naphthalene in 3 ml of glacial acetic
acid, then cool and add 1ml of conc. HNO3 and heat the mixture gently for
1 minute. Cool and pour the solution into a beaker which contains about 25
ml of cold H2O and note the separation of nitronaphthalene as a yellow
solid (1-,1,8-and 1,5-nitronaphthalene).
‐ 35 - IV- Compounds containing C, H,O and N
This class includes ammonium salts of acids, amides, imides, amines,
anilides, nitro compounds and amino acids.
IV-1- ammonium salts of acids:
IV-1-1- Grind in amorter, aportion of the substance with solid Na2CO3,
moisten wiyh afew drops of H2O, ammonia evolves.
IV-1-2- Add NaOH solution to the solid substance in a test tube, ammonia
is given on cold. The above two tests indicates ammonium salts of acids
now detect and identify the acid radical of the amm. salts as under metallic
salts of acids (III-7).
IV-2- Amides, imides and nitriles:
IV-2-1- Boiling with 30% NaOH solution:
Boil the compound, in a test tube with 30-40% NaOH solution (3-4 ml)
evolution of ammonia indicates the presence of an amide, imide or nitrile
group.
RCONH2 + NaOH
RCOONa + NH3
R(CO)2NH + 2NaOH
R(COONa)2 + NH3
RCN + NaOH + H2O
RCOONa + NH3
Amides liberate ammonia comparatively rapidly, whereas nitriles require
longer heating.
Identification of Amides, imides and nitriles:
‐ 36 - CONH2
CONH2
CH3CONH2
CONH2
Accetamide
Benzamide
Oxamide
H2N
NH2CONH2
C
NH2
S
Thiourea
Urea
O
O
H2C
C
NH
NH
H2C
C
O
O
Phthlimide
Succinimide
IV-2-2- hydrolysis of amides, imides and nitriles:
Place about 2g of the substance in a round bottom flask and 20 ml of
20% NaOH fit the flask with a reflux condenser and boil for about 0.5 h or
more. cool the flask and add excess dil. H2SO4 while cooling:
a) A white ppt. indicates an aromatic acid, filter, wash with cold water
and identify the acid as usual (amide of benzoic or phthalic acid).
b) No ppt. is formed. Then the acid is aliphatic, it is identified in the
usual way. (Acetic acid, Oxalic or succinic acid).
c) A brisk evolution of CO2 occurs but no ppt. indicates urea.
Na2CO3 + NH3
CO(NH2)2 + 2NaOH
‐ 37 - Confirmatory test:
IV-2-3- Biuret test (for urea and its salts):
Place 0.5 g urea in dry test tube, heat gently for 1-2 minutes and cool the
residue.
2CO(NH2)2
H2NCONHCONH2 (biuret) + NH 3
Dissolve the formed biuret in a few ml. of warm 10%NaOH.by cooling and
adding 1 drop of very dilute CuSO4 solution, a purple or violet colouration
is obtained.
HN
HN
H2N
CuSO4
HN
HN
O
OH
O
HN
Cu
O
OH
O
H2N
HN
Purple colour
HN
For differentiation
Acidity test
observation
-ve
+ve
Inference
Urea
Urea salts
- Aq. Soln + CaCl2
Urea oxalate give white ppt. insol.in ACOH acid
IV-2-4- For Oxamide:
Biuret test: shake 0.1 g of oxamide with 1 ml of 10% NaOH solution, add
1-2 drops of very dilute CuSO4 soln. and mix well. A pink colouration is
produced
IV-2-5- For succinimide:
It gives positive fluorescin reaction.
IV-2-6- For phthalimide:
It gives positive phthalein and flurescin reactions.
IV-3-primary aromatic amines:
IV-3-1- diazotization and coupling with β-naphtho:
Add dil. HCl to the substance in the test tube (the substance does not need
to dissolve completely in HCl). Cool in ice, then add cold alkaline solution
of β-naphtho in excess, a brilliant red dye indicates primary aromatic
amines.
‐ 38 - HO
N
NH2
NaNO 2 + HCl
N
NCl
N
B Naphthol
NaOH
Benzenediazonium chloride
Azo dye
IV-3-2- test for nitro group in the presence of amino group
Diazotize the amine as before. Stir the solution from time to time, wait for
10 minutes, then take a portion of the diazotised solution in a test tube and
boil it till all N2 gas is evolved. Cool in ice and couple (small amount)by
adding alkaline solution of b-naphthol, if a colour or ppt. is formed, this
indicates that the amino group is not removed completely. Continue
diazotizing step for the original solution by adding HCl and NaNO2 again
boil , then test a portion by coupling with β-naphthol soln. of no dye ia
ginen, then diazotization is complete. Next, boil the original soln. with Zn
and HCl for 10 minutes at least. This step destroys the diazonium
compound and reduces the nitro group to amino group. Cool again and
diazotize as before and couple, a red dye indicates the presence of a nitro
group.
NH2
O
N
N
OH
N
OH
-N
-H2O
NO2
NO2
o-Nitrobenzenediazonium hydroxide
OH
OH
Zn/HCl
(test for NH2)
NO2
NH2
Differentiation between nitro anilines
All nitro anilines are coloured yellow or orange compounds and are
soluble in hot water.
‐ 39 - NH2
NH2
NH2
NO2
NO2
NO2
m-Nitroaniline
o-Nitroaniline
p-Nitroaniline
IV-3-3- formyl derivatives as in IV-3-8.
o-nitri aniline m.p. 122oC
m--nitri aniline m.p. 134oC
p--nitri aniline m.p. 194oC
IV-3-4- test for –COOH group in the presence of amino group (acidity
test)
COOH
COOH
COOH
NH2
NH2
NH2
o-Aminobenzoic acid
m-Aminobenzoic acid
p-Aminobenzoic acid
Anthranilic acid
The above acids are sparingly sol. In cold H2O, sol. In minerl acids and
caustic alkalies, dissolve readily in alcohol.
IV-3-5- Confirmatory test:
a) Give aniline on heating with soda-lime
b) Give diazo-derivatives which couple with alkaline β-naphthol to give
an azo-dye.
c) Decompose on heating to give the corresponding phenolic
derivatives e.g. o-aminobenzoic acid yields salicylic acid.
d) Amide derivatives
Dissolve or suspend the requisite acid chloride of amino benzoic acid
in 5-10 ml. of dry ether or benzene and add concentrated ammonia
solution and warm for a few minutes in a water-bath. If no solid
separates, evaporate the solvent. Recrystallize the amide from water
or dil. Ethanol.
‐ 40 - If IV-3-2- and IV-3-4- are negative then detect for unsubstituted
aromatic amino compounds.
Differentiation between primary amines.
NH2
CH3
NH2
NH2
Naphthylamine
Naphthylamine
p-Toluidine
IV-3-6- boiling the solid substance with water:
observation
Inference
No oil drops
β-naphthylamine
Oily drops
P-toluidine or α-naphthylamine
IV-3-7- amine in dil. HCl+FeCl3
observation
Blue colour
-ve
Inference
α-naphthylamine
P-toluidine
Confirmatory test:
IV-3-8- formyl derivatives:
Formic acid condenses with primary and secondary aminesto yield
formyl derivatives:
ArNHR
+
ArN(CHO)R + H2O
HCOOH
Reflux 0.5 g. of the amino with 5 ml. of 90% formic acid (caution in
handling) for 10 minutes, and dilute the hot solution with 10 ml. of cold
H2O. cool in ice and, in some cases, saturate with salt if the derivative
does not separate immediately. Filter, wash with cold H2O and
recrystallize from water, ethanol or light petroleuim.
P-toluidine (formyl)
m.p. 53oC
α-naphthylamine
m.p. 139oC
β-naphthylamine
m.p. 129oC
IV-3-9- Action of bleaching powder (oxidation)
Shake 1-2 drops of amine with 10 ml. of H2O and add a few drops of
bleaching powder soln.(NaOCl), characteristic colour appears.
observation
Inference
Yellowish colour
P-toluidine
Pale brown
α-naphthylamine
‐ 41 - -ve
β-naphthylamine
IV-4- secondary aromatic amines:
IV-4-1- reaction with nitrous acid:
Nitrosamines are formed, these are usually yellow oils solids of low m.p.
and give the Liebermann's nitroso reaction.
IV-4-2- Liebermann's nitroso reaction:
Dissolve 0.1 g.of the secondary amine (unknown) in 3-5 ml. of dil. HCl or
ethanol (in the latter case, add 1 ml. of conc. HCl acid). Cool to about 5oC
and add 4-5 ml. of 10% NaNO2 soln. and allow to stand for 5 minutes.
Add10 ml. of water, transfer to a small separator funnel and extract the oil
with about 20 ml. ether. Wash the ethereal extract successively with water,
dil. NaOH solution and water. Remove the ether on a wormed water bath.
Place 1 drop or 0.01- 0.02 g. of the extracted nitroso compound in a dry test
tube, add 0.05 g. of phenol and warm together for 20 seconds, cool, and
add 1ml. of conc. H2SO4 acid. And an intense green (or greenish-blue)
colouration will be developed, which changes to pale red upon-pouring in
to 30-50 ml. of cold H2O the colour becomes deep blue or green upon
adding excess of NaOH solution.
R2NH
R2N-NO
+
R2N-NO + H2O
HONO
H2SO4
C6H5OH
HONO
N
HO
O
HO
NO
C6H5OH
Indophenol
NaOH
NaO
N
O
Diphenylamine (C6H5)2NH, m.p. 54oC
IV-4-3- Reactions:
a) Dissolve a few crystals of diphenylamine in 1 ml. of conc. H2SO4 or
H3PO4. Add 2 drops of conc. HNO3 to about 10 ml. of H2O. shake
and add one drop of this latter solution an intense blue colouration is
produced.
b) With FeCl3,diphenylamine give green colour
‐ 42 - c) N-Nitrosodiphenylamine Dissolve 0.5 g of diphenylamine in about 5
ml. of warm alcohol, then add 0.5 ml. HCl, cool in ice and add, drop
by drop, a cold soln. of 3 g of NaNO2 in 10 ml. H2O. leave the
reaction in ice for 4 minutes and then filter off the yellow crystals
which have separated, wash with water and carry out liebermann's
reaction as described before.
d) Simon's test:
To a suspension of diphenylamine (0.001 g.) in H2O (3 ml.),
add acetaldehyde (1 ml) and then 1% aq. Soln. of nitroprusside (2-3
drops). Adeep blue colour is developed with in5 min. which changes
gradually through greenish blue to pale yellow.
e) Carbon disulphide reagent test:
Prepare a soln. of diphenylamine (0.015 g) in dil. HCl (5.ml.) in a
test tube. Place the reagent (1 ml.) in an anther test tube, add conc. NH3
soln. (0.5-1 ml) and the amine soln. (0.5-1ml). a white (brown) colour
produced.
NH4Cl + H2O + R2N
R2NH + CS2 + 2NH4OH + NiCl
C
S
2Ni
S
N.B. test for thee nitro group
IV-5- Tertiary Amines:
N(CH3)2
N(C2H5)2
N
N,N-Dimethylaniline
N,N-Diethylaniline
Triphenylamine
IV-5-2- Reaction with nitrous acid:
The dialkylanilines yield green solid P-nitroso compounds.
(H3C)2N
(H3C)2N
HONO
NO + H2O
IV-5-2- Nessler's reagent test:
‐ 43 - In a test tube dissolve the compound (0.1 g) in dil. HCl and add into it
Nessler's solution. the appearance of a white ppt. indicates
tertiaryamines.
IV-5-3- action of nitric acid:
Dissolve a few crystals of amine in 1 ml. of conc. H2SO4. Add 2
drops of conc. HNO3 to about 10 ml. of H2O. shake, and add one
drop of this solution to the former one,
Deep yellow colour
Dimethylaniline
Intense greenish-blue
Triphenylamine
IV-6- Anilides R-CONHC6H5:
O
NHCOCH3
Acetanilide
HN
C
Benzanilide
IV-6-1- Hydrolysis with 70%H2SO4 test
Hydrolyse about 2 g. of the anilide with 20 ml. of 70% H2so4 (4
volumes of conc. H2so4 to 3 volumes of water) in a small flask fitted.
with a reflux condenser and boil for 20-30 minutes. In case of
acetanilide. distill the acetic acid, and test for aniline in the distilling
flask, while in case of benzanilide filter the ppt. (benzoic acid), purify
from any unchanged anilide by dissolving in Na2Co3 , filter then acidify,
and refilter the ppted .acid (then identify both amine and acid as usual).
IV-6-2- Anilides Give the Liebermann's nitroso reaction for
secondary amines (see IV-4-2)
IV-6-3- Dichromate test:
Place the compound (0.001 g) in a dry test tube, add conc. H2SO4, shak
the contents vigorously and then add finely powdered K2Cr2O7 (0.050.07 g). the immediate appearance of a bluish pink or deep blue colour
indicates anilide.
This is a positive test for those anilides which do not have
substituents in the ring.
IV-7- Test for Nitro Aromatic Compounds:
Nitro compounds are usually coloured, yellow to red. They react
vigorously with metallic sodium during the element test.
‐ 44 - IV-7-1- Reduction to the hydroxylamine with neutral reducing
agent:
Dissolve 0.5 g. of the substance in 10 ml. of 50% ethanol, add 0.5 g. of
solid NH4Cl and about 0.5 g. of Zn powder. Heat the mixture to boiling
for 5 minutes. Filter from axcess of Zn powder and test the filtrate with
Tollen's reagent. An immediate black or grey ppt. or a silver mirror
indicates the presence of –NO2 group (Fehling's soln. may be used).
Make sure that the original compound does not affect the reagent used.
RNHOH + H2O
RNO2 + 4H
RNO + 2Ag + 4NH3 + 2H2O
RNHOH + 2[Ag(NH3)2]OH
IV-7-2- Reduction to amino group:
NO2-group on reduction, is transformed to the primary amino group
which can be detected by diazotiasation and coupling.
Place about 0.5 ml. or 0.5 g. of the nitro compoundin small beaker, add
5 ml. conc. HCl and few pieces of granulated tin or Zinc. Warm gently
with stirring till all the compound has disappeared. Filter and pour into
about 20 ml. of water. Cool, carry out diazotiasation test and couple
with alkaline β-naphthol.
In order to separate the base, cool the solution after dilution, then add
NaOH soln. till alkaline and extract with ether. Separate the ethereal
layer and evaporate it, the amine is left behind. Identify as usual.
RNH2 + H2O
RNO2
IV-7-3- compound containing one or more NO2 group will oxidize
Fe(OH)2, the colour change is from green to brown.
RNH2 + 6Fe(OH)3
RNO2 + 6Fe(OH)2 +4H2O
For differentiation
IV-7-4-compound soln. + FeCl3
observation
Aviolet – red colour
-ve
Inference
Nitro-phenols
Mono-or dinitro hydrocarbons
IV-7-5-Nitro-Phenols:
‐ 45 - OH
OH
OH
NO2
NO2
o-Nitrophenol
m-Nitrophenol
NO2
p-Nitrophenol
The presence of the nitro-group renders the phenol acidic enough to
dissolve in NaCO3 soln. with the evolution of CO2.
o-Nitrophenol:
Bright yellow needles, m.p. 46oC, its oddour resembles both that of phenol
and of nitrobenzene, volatile in steam,sparingly soluble in cold water, sol.
In hot water.
m-Nitrophenol:
m.p. 95oC, sol. In hot water, non volatile in steam.
p-Nitrophenol:
yellow prisms, gradually turns red in light, m.p. 114oC, very sol. In hot
water.
General reaction:
a-NaOH:
the dissolve in sodium hydroxid solution giving on orange soln. the
colour is discharged an adding an acid, but is restored on making the soln.
alkaline
b- Na2CO3:
they dissolve in sodium carbonate solution with the evolution of
CO2
c- FeCl3:
when a few drops of FeCl3 are added to the nitrophenol solution, a
violt-red colour is produced. O-Nitrophenol does not give a colouration.
d- They do not give the liebermann's nitrose reaction.
e- Reduction:
they are reduced (as befor) to amino phenols (diazotize and couple).
The solution after reduction does not give a colouration when rendered
alkaline with NaOH.
IV-7-6- Nitro Hydrocarbons:
‐ 46 - NO2
NO2
NO2
Nitrobenzene
m-diNitrobenzene
Nitrobenzene:
A pale yellow liquid, insol. In water and heavier than water, with a
characteristic odour of bitter almonds. On reduction as before it gives
aniline which can be identified as usual.
m-Dinitrobenzene:
A pale yellow solid, m.p. 90oC, insol. In water
General reaction:
a- Acetone alkali colouration: dissolve a few crystals in 1-2 ml. of
acetone, then add a few drops of aqueous NaOH solution, adeep
colouration is produced, and it turns red by acetic acid, but destroyed
by mineral acids.
b- It is reduced in acid solution to m-phenylenediamine NH2C6H4NH2
which:
1) On diazotization and coupling, a deep-brown soln. or a brown
ppt. of the dye Bismark brown appears.
2) When a few drops of FeCl3 is added to a very dil. Soln. of the
base in water, a reddish colouration appears.
IV-8- Test for Amino acid:
H2N
H
C
COOH
R
IV-8-1- Ninhydria test:
Place 2-3 drops of 0.2%aq.soln. of ninhydrin on a piece of filter paper
followed by drying it in air (or oven).Drop aq. Soln. of amino acid (1
drop) on this paper and redry it for afew minutes, Ablue (sometimes violet)
spot or ring appears on the paper.
‐ 47 - O
C
CH(OH)
H
C
H2N
C
-H2O
COOH
-CO2
R
O
Ninhydrin
O
O
C
C
C
C
NCH2R
N
CHR
H2O
C
C
OH
O
O
C
C
RCHO
NH2
Ninhydrin
-2H2O
C
OH
O
O
C
C
C
N
C
C
C
OH
O
Blue-violet
‐ 48 - V- COMBINATION OF SULPHUR
This class includes: alkaline bisulphate addition compounds of
aldehydes and ketones, alkyl sulphates, addition compounds of amines with
sulphuric acid, sulphonic acid, sulphonic acids and their salts
V-1- Alkaline bisulphate addition compounds of aldehydes and ketones
:
Heat the solid substance in a crucible, note the odour of the evolved
aldehyde or ketone . the residue left in the crucible is tested for sulphite and
sulphate. (add dil. HCL, SO2 gas is evolved known by its odour of burnt
sulphur and turns acidified dichromate paper green).
R-CH (OH)SO3Na + HCL
RCHO + NaCL + SO2 + H2O
V-2-Ionisable sulphate:
Dissolve the substance in water (or alcohol) and add barium nitrate soln. a
white ppt. of barium sulphate, indicates ionisable sulphate, e.g. aniline
sulphate (it must be taken into consideration that some salts of acids which
are sol. In water may pptate the barium salt of the acid).
C6H5NH2H2SO4 + Ba(NO3)2
C6H5NH2 + BaSO4 + 2HNO3
V-3- hydrolysable sulphate:
Boil the substance with NaOH soln. then acidify the soln. strongly with
nitric acid ( if a ppt. appears, filter and use the filtrate) and add barium
nitrate soln., awhite ppt. indicates hydrolysable sulphate.
S=C(NH2)2 + 2H2O
CO2 + H2S + 2HN3
V-4- sulphonic acids:
If the above tests are negative, the sulphur present is directly linked to the
aromatic nucleus, most probably sulphonic acid group or fuedthe substance
with solid sodium hydroxide. Sulphonic acid group is decomposed into
sodium sulphite and sodium sulphate. Dissolve in water, acidify with dil.
Acid, add barium nitrate solution, a white ppt. is produced.
OH
SO3H
NaOH
NaHSO3
Na2SO4
BaCl2
NH2
NH2
NaCl + BaSO White ppt.
HCl
NaCl + H2O + SO2
V-5-sulphonamide group (-SO2.NH2):
‐ 49 - Fuse the compound (0.5 g.) with KOH (2 g.) in a tube for 10 minutes and
bring a filter paper moistened with saturated ethanolic 2,4dinitrochlorobenzene solution. The appearance of a strong yellow colour on
the paper indicates sulphonamide.
Fusion with 80% H2SO4 at 160-170 o results in rapid hydrolysis.
ArSO2NRR' + H2O
ArSO2OH + RR'NH.H2SO4
The reaction product may then be examined for asulphonic acid and an
amine.
For differentiation:
SO3H
NH2
H2SO4
(NH2)2C=S
thiourea
Aniline Sulphate
NH2
Sulphanilic acid
a) Acidity test:
observation
inference
Aniline sulphate or Sulphanilic
acid
thiourea
+ve
-ve
b) Compound soln. +BaCl2:
observation
A white ppt. insol. In dil. acids
-ve
inference
Aniline sulphate
Sulphanilic acid
c) Azo-dye test
observation
inference
Deep yellow orange
Sulphanilic acid
Scarler red
Aniline sulphate
d)
Mercury oxide removes a molecule of H2S from
thiourea at room temperature to form cyanamide.
(NH2)2CS + HgO
H2NCN + HgS + H2O
Black
‐ 50 - e)
Oxidation with alkaline
KMNO4 (removes its violet colour) converts thiourea into urea.
(NH2)2C=S + [O]
(NH2)2C=O + S yellow
VI- COMBINATION OF SULPHUR
This class includes: halogenated aldehydes and ketones, e.g. chloral
hydrate, acid halides, halogenated hydrocarbons, acids or phenols.
VI-1- ionisable halogen:
Dissolve the substance in water (or alcohol), add AgNO3 soln., a ppt.
indicates ionisable halogen e.g. amine salts, acid chlorides.
N.B.: acid chlorides specially aliphatic, are very easily hydrolysable in
contact with water, that they give ppts. When treated with AgNO3 and
appear as if they contain ionisable halogen.
C6H5NH2.HCl + AgNO3
C6H5NH2 + AgCl + HNO3
VI-2- Hydrolysable halogen (aliphatic combination):
Hydrolyse by boiling the substance with 30% NaOH soln. for some time,
cool, acidify with dil. Nitric acid (filter from any ppt. formed). And add
AgNO3 soln. a ppt. indicates a hydrolysable halogen (halogen attached to
an aliphatic linkage or to an aromatic side chain). e.g. chloralhydrate.
VI-3-Non-hydrolysable halogen (aromatic combination):
IF the above tests are negative then the halogen is in aromatic linkage
(directly linked to an aromatic nucleus).
For Differentiation:
NH2
CCl3CHO.H2O
Aniline hydrochloride
CHI3
Chloralhydrate
Iodoform
a) Acidity test:
observation
+ve
-ve
inference
Aniline hydrochloride
Iodoform or chloral hydrate
violet fumes
b) Action of heat:
CHCl3 evolves.
c) Treatment with NaOH:
d) Reduction (for chloral hydrate):
Iodoform
Chloralhydrate
‐ 51 - CCl3CHO
CCl3-COOH
With Tollen's reagent
a silver mirror
With Fehling 1 and 2
Red ppt. of Cu2O
e) Azo-dye test:
Scarlet red dye
aniline hydrochloride
Lastly
1) The melting point of the original compound is recorded, (or the
boiling point)
2) After the group in the compound has been ascertained, asuitable
solid derivative (which depends upon the group present) is prepared
and its m.p. is determined.
3) The compound is then identified if possible.
‐ 52 -