ALDEHYDES & KETONES - PowerPoint PPT Presentation

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aldehydes ketones n.
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ALDEHYDES & KETONES

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  1. ALDEHYDES & KETONES

  2. HCHO or ketones Aldehydes

  3. Physical properties State Color Odor Colorless Pungent Formaldehyde Liquid, mobile, solution Liquid, mobile, true Pungent Acetaldehyde Colorless Liquid, mobile, true Colorless Characteristic odor Acetone Chlorahydrate Solid, crystalline White Characteristic odor Colorless Bitter almond odor Benzaldehyde Liquid, oily, true Characteristic odor Liquid, oily, true Colorless Acetophenone

  4. Aliphatic Inflammable, non luminous, non smoky Aliphatic Volatilization Aliphatic No residue for all No change for all No change for all Non inflammable Melting Aliphatic Aromatic Inflammable, luminous, smoky Volatilization Aromatic

  5. Miscible // no change Miscible // no change Miscible // no change no change Soluble // Immiscible in all Immiscible in all All the compounds are neutral Comment

  6. Sweety odor of chloroform odor It is done for compound with no α hydrogen (( Self oxidation – reduction reaction)) On hot Called Cannizzaro’s reaction [Difficult to be done] All aromatic aldehyde & only formaldehyde goes cannizzaro’s reaction Dil. acetal.+ xss 30%NaOH Sweety odor of chloroform odor + droplets of oil No α hydrogen No reaction No reaction (Acetone & Acetoph.) Cannizzaro’s reaction Yellow resin + bad apple odor ((Called aldo condensation)) No reaction Undergoes cannizzaro’s reaction Methanol + formic acid No reaction White ppt ((it is difficult to be done)) Not done Not done (Acetone & Acetoph.)

  7. No reaction for all No reaction for all No reaction No reaction Separation of an oily layer of Chloral No reaction Not done No reaction

  8. 1] 2, 4 – dinitrophenyl hydrazine test: Reagent A Reagent B For aldehyde & ketones immiscible in H2O For formaldehyde & ketones miscible in H2O For aromatic {Benzaldehyde & Acetophenone} For aliphatic {Formaldehyde, Acetaldehyde, Chlorahydrate, Acetone} Aldehyde or ketones + 3 drops from reagent A or Bshaking Formal. Acetal. Chlora. Benzal. Acetone Acetoph. Orange ppt Yellow ppt Yellow– orange ppt No reaction Orange ppt Orange– yellow ppt

  9. 2] Silver mirror test = Tollen’s reagent test = Ammonical silver nitrate test: Few ml of silver nitrate + 1 drop 10% NaOH Black ppt of Ag2O + dil. NH4OH ((until clear solution obtained)) (1) Called Tollen’s reagent 1ml of Tollen’s reagent + 1ml aldehyde or ketones [ heat on water bath 10 min.] cool on the rack (2) NOTE:Reagent 1st then aldehyde or ketones Acetoph. Formal. Acetal. Chlora. Benzal. Acetone Rapidly gives silver mirror No reaction Silver mirror after longer time on the water bath

  10. 3] Fehling reagent test = Fehling reduction test: Fehling A Fehling B In test tube mixequal amount of Fehling A + Fehling B Blue color (1) In test tube few aldehyde or ketones + few Na2CO3 + (Fehling A + B) heat on water bath (2) Formal. Acetaldehyde Chlora. Benzaldehyde Acetone Acetophenone Rapidly change in color Change in color take longer time No reaction