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QUANTITATIVE DETERMINATION OF ALDEHYDES AND KETONES

QUANTITATIVE DETERMINATION OF ALDEHYDES AND KETONES. BY SRAVAN. S. INDEX. INTRODUCTION METHODS OF QUNATITATIVE DETERMINATION SPECTROSCOPIC METHODS CHROMATOGRAPHIC METHODS. Aldehydes and ketones can be determined by using following 3 reagents Hydroxylamine hydrochloride – Pyridine

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QUANTITATIVE DETERMINATION OF ALDEHYDES AND KETONES

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  1. QUANTITATIVE DETERMINATION OF ALDEHYDES AND KETONES BY SRAVAN. S

  2. INDEX • INTRODUCTION • METHODS OF QUNATITATIVE DETERMINATION • SPECTROSCOPIC METHODS • CHROMATOGRAPHIC METHODS

  3. Aldehydes and ketones can be determined by using following 3 reagents • Hydroxylamine hydrochloride – Pyridine • Sodium sulphite – Sulphuric acid • 2,4 – Dinitro phenyl hydrazine

  4. METHOD - 1 • Hydroxylamine hydrochloride+carbonyl compounds HCL+OXIME Pyridine Pyridine hydrochloride

  5. ALDEHYDE H H R-C=O + NH2OH.HCL R-C=NOH + H2O + HCL H H R-C=O + NH2OH.HCL + C5H5N R-C=NOH + C5H5N.HCL + H2O

  6. KETONE R R-C=O+ NH2OH.HCL + C5H5N R R-C=NOH+C5H5N.HCL+H2O C5H5NHCL + NaOH C5H5N + NaCL + H2O

  7. The reaction of the carbonyl compound with hydroxyl amine reaches equilibrium which is displaced to the right in presence of pyridine and excess of hydroxyl amine hydrochloride. • The rate of reaction depends upon the structure of –R group,lower aldehydes like and ketones give quantitative reaction in about 30min at room temp, wher as ketone like acetophenone, benzophenone benzoin requires 2hrs heating at 100 degrees centigrade.

  8. METHOD-II Carbonyl compounds +sodium bisulphate Crystalline bisulphite It is determined Iodometrically or by titration R-CHO+NaHSO3 RCH(OH)SO3Na

  9. METHOD -III 2,4-dinitrophenyl hydrazine+carbonyl compound 2,4-dinitrophenyl hydrazone NHNH2 NO2 NO2 R R R-C=O + R-C=N-NH- NO2 NO2 O O

  10. Determination of ketone using 2,4-dinitrophenyl hydrazine • Take 0.2g of camphor in a stopper flask, add 25ml of aldehyde free alcohol to dissolve the sample, with swirling add 75ml of 2,4-dinitrophenyl hydrazine reagent and reflux on a water bath for 4hrs • Remove the alcohol by distillation, cool add 200ml of 2% v/v solution of Sulphuric acid

  11. 2,4-dinitrophenyl hydrazone is collected in sintered glass crucible • The ppt is washed with 10ml quantities of water till filtrate is neutral to litmus. • Dry the ppt at 80°c cool and weigh The percentage of camphor can be calculated by the factor given below Each gram = 0.458g of camphor % of camphor = W x 0.458 x 100 1 x A

  12. Determination of Aldehyde by sodium sulphite reagent • 250ml of Sodium sulphite solution in a suitable stoppered flask, add 50ml of 1N sulphuric acid • To the above sol add accurately weighed quantity of about 20-30 mini-equivalent of aldehyde and shake vigorously for 14min. • Intorduce the glass-calomel electrode system in the beaker and connect to pH meter. Titrate the excess of acid with standard 1N alkali solution. • % of Aldehyde = (y-x) x N x M x 100 W x 1000

  13. UV-VISIBLE SPECTROSCOPY • The carbonyl group contains a pair of Π electrons and 2 pairs of non-bonding n or p-electrons, in addition to a pair of σ electrons • Saturated ketones and aldehydes exhibit 3absorption peaks .They are 1.Π – Π* 2. n – σ* 3. R - band

  14. Carbonyl groups present in aldehydes and ketones have significant effect upon the n-Π* transitions. • The R-band gets shifted to shorter wavelength with a slight change in intensity. The shift in absorption is due to a combination of inductive and resonance effects. • Substitution may change the energy levels of both the ground and excited states

  15. INFRARED SPETROSCOPY • A Strong absorption band in the region around 1700 is due to c=o stretching • The carbonyl groups of aldehydes generally absorb at 10-15cm-1higher frequencies than the corresponding ketones. • Thus 3-pentanone shows a c=o stretch at 1715cm-1 ,aliphatic aldehydes absorb near 1740-1720cm-1.

  16. Majority of aldehydes show aldehyde C-H stretching absorptions in the region 2900-2695 cm-1. Two moderately intense bands at are frequently observed in the region 2900-2695cm-1and diferentiate aldehyde class or compounds from other carbonyl compounds • The important difference between an aldehyde and ketone is there an aldehyde has a H-bonded to the carbonyl compounds. • The important difference b/w an aldehyde and ketone is that an aldehyde has a H-bonded to the carbonyl carbon.

  17. The aromatic aldehyde , ex: p-tolualdehyde shows its aldehydic C-H stretch at 2830 and 2736cm-1 • The carbonyl stretching frequency of a pure sample of saturated aliphatic aldehyde around 1725cim-1 that of a ketone at 1710cm-1 .

  18. IR FREQUENCIES FOR ALDEHYDES AND KETONES ALDEHYDES Group/Vibrations Frequencies cm-1 C = O Stretching • Saturated acyclic 1740 – 1720 • Alpha,beta-unstaurated, acyclic 1710 – 1685 • Aryl 1715 – 1695 C – H stretching 2900 – 2695 C – H bending 975 - 780

  19. KETONES: C =O Stretching • Saturated acyclic 1725 – 1705 • Alpha,beta unsaturated , acyclic 1685 – 1665 • Aryl 1685 – 1665 C – H stretching 3000 - 2900

  20. MASS SPECTORMETRY Some important features of the mass spectra of aliphatic aldehydes and ketones are • The Intensity of the molecular ion peak decreases as the alkyl chain length increases • The major fragmentation processes are ά and β clevage . • In aldehydes and ketones containing γ-hydrogen atom.McLafferty rearrangement ion is most significant. In an aldehyde, which is not ά-substituted , apeak due to this is fored at m/e 44. It may be base peak.

  21. In lower aldehydes, ά- clevage is prominent with retention of clevage on oxygen. • In Aromatic aldehydes and ketones parent ion peak is intense. • In ketones, the loss of larger group is preferred by a ά- clevage.

  22. HPLC KETONE: Formulation: Thymol,methylsalicylate, Camphor and salicylic acid. Sample preparation: Sample suspended in 100ml of solvent, warmed in water bath(60c) and shaken for 10min. Centrifuged and supernatant used for analysis. Standard Preparation: Solution of each ingredient is prepared in solvent. [water-THF- methanol]

  23. Internal Standard: Diphenhydramine Hcl - 100µg/ml in solvent. • HPLC System: Shimadzu LC system. • Column: Shimpak CLC – DDS Column, 150 x 6mm • Chromatographic conditions: Compositon of mobile phase and its PH: 200mM sodium perchlorate in 10mM sodium phosphate. PH: 2.6 – Methanyl acetonitrile • Flow rate: 1.5ml/min • Volume Injected: 20 µl

  24. Wave length: UV – 210nm • Retention time: Salicylic acid - 3 Diphenhydramine Hcl - 3.9 Methyl Salicylate - 6.1 Camphor - 7.2 Thymol - 9.5

  25. ALDEHYDE • Formulation: Betamethasone valerate, clotrimazole, Benzaldehyde. • Sample Preparation: weigh 0.64mg of Betamethasone or 10mg of clotrimazole, add 2ml of standard solution and 8ml of methanol. Heat in waterbath(60c) for 10min,cool,centrifuge and filter. • Standard Preparation: Betamethasone dipropionate - 320µg/ml clotrimazole - 5mg/ml Both the solutions are prepared in methanol, mixed standard solution

  26. Column: Suplex PKB – 100 column, 250 x 4.6mm • Conditions: Composition of MP and its PH Acetonitrile – Tetrahydrofuran – 15mm Acetate buffer – PH – 4 • Flow rate: 2ml/min • Volume Injected: 10µl • Wave length: U.V – 254nm • Retention time: Benzaldehyde – 3.3 clotrimazole - 7.7

  27. THANK YOU

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