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Questions of the Day: Which test allows you to distinguish between 1) an aldehyde and a ketone?

Questions of the Day: Which test allows you to distinguish between 1) an aldehyde and a ketone? 2) an aldehyde and a primary alcohol? 3) an alcohol and a phenol?.

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Questions of the Day: Which test allows you to distinguish between 1) an aldehyde and a ketone?

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  1. Questions of the Day: Which test allows you to distinguish between 1) an aldehyde and a ketone? 2) an aldehyde and a primary alcohol? 3) an alcohol and a phenol?

  2. Today:“Unknowns” - Review of Preliminary Tests and SolubilitiesUnknown #1:- Classification tests and derivatives for:Aldehydes and KetonesAlcohols and Phenols Family Science Night Volunteers meet after next Tuesday’s Lablecture Next time: Unknown #2:Carboxylic Acids, Esters, Amides. Amines.

  3. Preliminary TestsAldehydes and KetonesAlcohols and Phenols • Mp. for solids (What needs to be remembered for a good mp.measurement?) • Bp. for liquids • Refractive index for liquids a physical characteristic, defines a compound • Ignition test information? • Test for unsaturation • Beilstein test for halogen (p.626)

  4. Solubility Tests (pp. 626 – 627) What type of information do you get if your unknown 1. is soluble in water? 2. is soluble in NaOH and in NaHCO3? 3. is soluble in NaOH only, not in NaHCO3? 4. is soluble in dilute HCl solution? 5. is soluble only in conc H2SO4? 6. is not soluble in any of the above solvents?

  5. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Aldehydes and Ketonesfunctional group? • Typical properties…. • Mp., bp., solubility…

  6. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Aldehydes and Ketones IR: H-NMR:

  7. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Classification Tests for Aldehydes and Ketones 2,4-dinitrophenylhydrazone • also a good derivative! • What are desirable properties of a derivative? • What is the purpose of preparing a derivative? • →Prepare two good derivatives of each unknown. Recrystallize from ethanol/water.

  8. Aldehydes and Ketones To distinguish between aldehydes and ketones: • Preliminary tests • Solubility • Classification tests • Derivatives • Spectra • Tollens Test: • Jones (chromic acid): check reagent! Test is also positive for …..? • Schiff reagent: check reagent! • Always do with a known compound to compare!

  9. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Aldehydes and Ketones DerivativesImines:2,4-dinitrophenylhydrazoneoximesemicarbazone

  10. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Alcohols and PhenolsSolubility distinction? Solubility: Alcohols: “neutral”; Phenols: very weak acids, pKa around 10, except nitrophenols! • Classification tests: • Jones (also positive with 1o, 2o alcohols, amines…!) • Lucas test for 3o alcohols, 2o alcohols (slow): • Phenols only: Complexation with Fe 3+

  11. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Alcohols IR: H-NMR: Exchange with D2O

  12. Phenols Sample Compound: Phenol IR H-NMR

  13. Preliminary tests • Solubility • Classification tests • Derivatives • Spectra Alcohol and Phenol Derivatives • with 3,5-dinitrobenzoyl chloride • urethanes Similarly: Naphthyl urethanes

  14. Anthocyanin Colors:Phenolic plant pigments responsible for blue, purple, pink colors in plants. Can complex with metal ions in soil, are pH sensitive

  15. Next time: • Unknown #2: • Carboxylic Acids, Esters, Amides • Amines • (Cl, Br, nitro) • MiniQuiz on today’s class!

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