Functional Group
Analysis
Functional Group Analysis
• Classical methods of analysis
(wet chemical analysis)
analyte + reagent = color or ppt.
 Main steps:
1. sampling
2. field sample pretreatment
3. Laboratory tretment
4. Laboratory assay
5. Calculation
6. Result presentation
Instrumental methods
Involve the use of instrument
They are:
1. Spectral
2. Electro-analytical
3. Separatory
Classical qualitative analysis
Classical quantitative analysis
Classical qualitative analysis
To deduce the identity of the analyte
 Add reagents that chosen one or single class of chemical compounds
(selectivity )
 Form ppt. or a gas or color with reagent
 Other measurements as b.p, m.p, , density ….
 Examples: addition of Br2 to identify the C=C….

Reaction used to identify the organic molecules
(condensation, diazodization, diazocoupling….)
Classical quantitative analysis
Volumetric analysis (titrimetric analysis) : acid – base , redox ,
complexometric, preciptmetry that give change in colour with indicator
at the e.p at certain volume of titrant
Gravimetric analysis: form ppt. with analyte , filtred, dried and
weighed
Examples of functional group analysis
- OH
1. Acylation
(esterification)
2. Non-aqueous titration
3. Bromination
4. Periodic acid oxidation
5. spectrophotometry
- C=O
1. Oximation
2. Hydrazone formation
3. Condensation with
active methylene
Amines
1. Acid – base titration
2. Condensation (1ry amine) with
carbonyl compounds
3. Reaction with 9-chloroacridine
4. With formaldehyde/acetone
5. Diazotization and diazocoupling
6. Charge – transfer
7. Ion-pair complexation
Thiol
1. AgNO3
2. Br2
- COOH
1. Acid – base titration
2. Saponification
3. Reaction with ferric
hydroxamete
Others
1. Zeissel method for
OR/N-alkyl group
2. Drug with reducing
activity
3. Binary complex
formation
4. Ternary complexation
reaction
Hydroxyl group –OH
alcoholic, glycols, enols and phenols
1. Acylation (esterification):
acid
alcohol
ester
Acid chloride or acid anhydride is used as they more potant than the parent acid
2. Non aqueous titration
Phenols and enols are weak acidic compounds can dermined by
titration with NaOCH3 in DMF and thymol blue as indicator
3. Bromination of phenolic compounds
The excess bromine
liberate iodine from KI
and titrated against
NaS2O3 using starch as
indicator
Aromatic amines undergo the same reaction so interfere in this analysis. Also
unsaturated compounds interfere by addition of bromine
4. Periodic acid oxidation of 1,2- glycol
Propylene glycol:
CH3CHOHCH2OH + 2 HIO4 = CH3CHO + HCHO + HIO3 + H2O
excess
KI
I 2 titrated using Na2SO4
Glycerol
NaOH
CH2OH-CHOH-CH2OH + 2HIO4 = 2CH2O + HCOOH + 2HIO3 + H2O
HCOOH + NaOH = HCHO + H2O
1 glycerol = 1 NaOH using bromocresol green as ind. (dis. Glycol)
5. Spectrophotometry
1. By coupling with Diazonium salt (azo dye)
2. Nitrosation
3. Coupling with antipyrine in presence of oxidizing agent
Carbonyl group –C=O
aldehyde/ ketons
1. Oximation
Oximes can be formed by the action of hydroxylamine on aldehydes or
ketones
2. Hydrazone formation
3. Condensation with Active methylene group
• Aldehyde and ketones form highly conjugated reaction
product with these reagents
Knoevenagel condensation
Chlorobenzaldehyde
Yellow colour product
Carboxylic acid and their derivative
- COOH
RCOOH
 RCOOR’
RCONHR’
RCONHCOR’ (imide)
(RCO)2O
RCOCl
imide
Carboxylic-acid-anhydride
Acyl-chloride
Carboxylic acid
Ester
Amides
1. Acid – base titration
2. Saponification
3. Ferric hydroxamate (Esterification and the hydroxamic acid test)
Esters react with hydroxylamine in basic solution to form hydroxamic acids,
which in turn react with ferric chloride in acidic solution to form bluish red
ferric hydroxamate
Amines – NH
1ry amine
1. Condensation with carbonyl
compounds
2. Reaction with 9-chloroacridine
3. formaldehyde/acetone
4. Diazotization and diazocoupling
2nd amine
CS2 + KOH + Cu
3rd amine
1. Charge – transfer
2. Ion-pair complexation
1. Primary amine:
1. Condensation with carbonyl compound
Schiff’s base (spectrophotometry)
2. Reaction with 9- chloroacridine:
3. Reaction with formaldehyde/ acetone
• Hantzsch pyridine synthesis
Reaction with dansyl chloride (dansylation)
Fluorescent product
4. Diazotization and diazo-coupling
2. Secondary amine:
3. Tertiary amines
• Charge transfer method:
Complexes between , Electron donor (amines and their derivatives):
electron acceptor (chloranil, p-chloranailic acid, iodine ….)
Acceptor
Donner
• Ion – pair complex
B+ + A -
AB
Amines
famotidine
methyl orange,
bromothymol blue ,
salicylate ….
Thiol, sulphide, disulphide
-SH , RSR, RSSR
RSH + AgNO3 = RSAg + HNO3
RSR + Br2
= RSOR + HBr
RS-SR + Br2 = 2 RSO2Br +HBr
Miscellaneous
1. Zeisel’s method (for Alkoxy OR, and N-Alkyl):
alkoxy group is treated with hydrogen iodide and the alkyl halide formed is further
treated with silver nitrate to precipitate silver iodide, collected and weighed
CH3OC2H5 + 2 HI = CH3I + C2H5OH
Volatile
Methyl or ethyl iodide only
piroxicam
indomethacin
2. Drugs with reducing activity:
When 1,10-phenanthroline is added to even a
dilute solution of iron(II), the highly colored
complex ion [Fe(phen)3]2+ is produced.
3. Binary complex:
Drugs containing NH2 and - COOH form complex with Metals
extractable with organic solvent .
Example mefenamic and flufenamic acid contain NH and COOH
form blue colour complex with copper in alkaline medium and
purple with iron in acid medium
4. Ternary complex formation (Ln Mx Sy)
 Used in spectrophotometric analysis
 More sensitive than the birany complex
 The complex of SCN, Cr(III), Zn(II), Co(II), Fe(III) are widely used.
metal
Ligand
Ofloxacine
Drug
(Ln Mx Sy)