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Functional Group Analysis

Functional Group Analysis

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Functional Group Analysis

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  1. Functional Group Analysis

  2. Functional Group Analysis • Classical methods of analysis(wet chemical analysis) analyte + reagent = color or ppt. • Main steps: • sampling • field sample pretreatment • Laboratory tretment • Laboratory assay • Calculation • Result presentation Instrumental methods Involve the use of instrument They are: Spectral Electro-analytical Separatory Classical qualitative analysis Classical quantitative analysis

  3. 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

  4. Examples of functional group analysis

  5. Hydroxyl group –OH alcoholic, glycols, enols and phenols • Acylation (esterification): Acid chloride or acid anhydride is used as they more potant than the parent acid ester alcohol acid

  6. 2. Non aqueous titration Phenols and enolsare weak acidic compounds can dermined by titration with NaOCH3 in DMF and thymol blue as indicator

  7. The excess bromine liberate iodine from KI and titrated against NaS2O3 using starch as indicator 3. Bromination of phenolic compounds Aromatic amines undergo the same reaction so interfere in this analysis. Also unsaturated compounds interfere by addition of bromine

  8. 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)

  9. 5. Spectrophotometry • By coupling with Diazonium salt (azo dye) • Nitrosation • Coupling with antipyrine in presence of oxidizing agent

  10. Carbonyl group –C=Oaldehyde/ ketons • Oximation Oximes can be formed by the action of hydroxylamine on aldehydes or ketones

  11. 2. Hydrazone formation

  12. 3. Condensation with Active methylene group • Aldehyde and ketones form highly conjugated reaction product with these reagents Knoevenagelcondensation

  13. Chlorobenzaldehyde Yellow colour product

  14. Carboxylic acid and their derivative- COOH • RCOOH • RCOOR’ • RCONHR’ • RCONHCOR’ (imide) • (RCO)2O • RCOCl Carboxylic acid imide Ester Carboxylic-acid-anhydride Acyl-chloride Amides

  15. Acid – base titration • Saponification • Ferric hydroxamate(Esterification and the hydroxamic acid test) Esters react with hydroxylamine in basic solution to form hydroxamicacids, which in turn react with ferric chloride in acidic solution to form bluish red ferric hydroxamate

  16. Amines – NH

  17. 1. Primary amine: • Condensation with carbonyl compound • Schiff’s base (spectrophotometry)

  18. 2. Reaction with 9- chloroacridine:

  19. 3. Reaction with formaldehyde/ acetone • Hantzsch pyridine synthesis

  20. Reaction with dansyl chloride (dansylation) Fluorescent product

  21. 4. Diazotization and diazo-coupling

  22. 2. Secondary amine:

  23. 3. Tertiary amines • Charge transfer method: Complexes between , Electron donor (amines and their derivatives): electron acceptor (chloranil, p-chloranailic acid, iodine ….) Acceptor Donner

  24. Ion – pair complex AB B+ + A- Amines methyl orange, bromothymol blue , salicylate …. famotidine 

  25. Thiol, sulphide, disulphide-SH , RSR, RSSR RSH + AgNO3 = RSAg + HNO3 RSR + Br2 = RSOR + HBr RS-SR + Br2 = 2 RSO2Br +HBr

  26. Miscellaneous • 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

  27. 2. Drugs with reducing activity: When1,10-phenanthrolineis added to even a dilute solutionof iron(II), the highly colored complexion [Fe(phen)3]2+ is produced.

  28. 3. Binary complex: Drugs containing NH2and - COOH form complex with Metals extractable with organic solvent . Example mefenamic and flufenamicacid contain NH and COOH form blue colour complex with copper in alkaline medium and purple with iron in acid medium

  29. 4. Ternary complex formation (Ln MxSy) • 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 MxSy)