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Aldehydes and Ketones

Aldehydes and Ketones. Before you can learn about aldehydes and ketones, you must first know something about the nomenclature of carboxylic acids since many of the names of aldehydes and ketones are derived from the names of the corresponding carboxylic acids. Carboxylic acids:

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Aldehydes and Ketones

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  1. Aldehydes and Ketones

  2. Before you can learn about aldehydes and ketones, you must first know something about the nomenclature of carboxylic acids since many of the names of aldehydes and ketones are derived from the names of the corresponding carboxylic acids.

  3. Carboxylic acids: R-COOH, R-CO2H, Common names: HCO2H formic acid L. formica ant CH3CO2H acetic acid L. acetum vinegar CH3CH2CO2H propionic acid G. “first salt” CH3CH2CH2CO2H butyric acid L. butyrum butter CH3CH2CH2CH2CO2H valeric acid L. valerans

  4. Carboxylic acids, common names: … CH3(CH2)4CO2H caproic acid L. caper goat CH3(CH2)5CO2H --- CH3(CH2)6CO2H caprylic acid CH3(CH2)7CO2H --- CH3(CH2)8CO2H capric acid CH3(CH2)9CO2H --- CH3(CH2)10CO2H lauric acid oil of lauryl

  5. 5 4 3 2 1 C—C—C—C—C=O δ γ β α used in common names

  6. Special names!

  7. ALDEHYDES AND KETONES “carbonyl” functional group: Aldehydes Ketones

  8. Nomenclature: Aldehydes, common names: Derived from the common names of carboxylic acids; drop –ic acid suffix and add –aldehyde. CH3 CH3CH2CH2CH=O CH3CHCH=O butyraldehyde isobutyraldehyde (α-methylpropionaldehyde)

  9. Aldehydes, IUPAC nomenclature: Parent chain = longest continuous carbon chain containing the carbonyl group; alkane, drop –e, add –al. (note: no locant, -CH=O is carbon #1.) CH3 CH3CH2CH2CH=O CH3CHCH=O butanal 2-methylpropanal H2C=O CH3CH=O methanal ethanal

  10. Ketones, common names: Special name:acetone “alkyl alkyl ketone” or “dialkyl ketone”

  11. (o)phenones: Derived from common name of carboxylic acid, drop –ic acid, add –(o)phenone.

  12. Ketones: IUPAC nomenclature: Parent = longest continuous carbon chain containing the carbonyl group. Alkane, drop –e, add –one. Prefix a locant for the position of the carbonyl using the principle of lower number.

  13. Physical properties: polar, no hydrogen bonding mp/bp are relatively moderate for covalent substances water insoluble (except: four-carbons or less)

  14. Spectroscopy: IR: C=O stretch, strong ~1700 cm-1 RCHO 1725 ArCHO 1700 R2CO 1710 ArCOR 1690 C—H stretch for aldehydes 2720 nmr: -CHO 9-10 ppm

  15. acetophenone C=O stretch

  16. valeraldehyde CHO C—H stretch 2720 cm-1 C=O stretch

  17. valeraldehyde CH3CH2CH2CH2CH=O a b c d e -CHO

  18. Oxidation/Reduction: oxidation numbers: oxidation -4 -2 0 +2 +4 CH4 CH3OH H2C=O HCO2H CO2 alkane alcohol aldehyde carboxylic acid reduction

  19. Aldehydes, syntheses: • Oxidation of 1o alcohols • Oxidation of methylaromatics • Reduction of acid chlorides • Ketones, syntheses: • Oxidation of 2o alcohols • Friedel-Crafts acylation • Coupling of R2CuLi with acid chloride

  20. Aldehydes synthesis 1) oxidation of primary alcohols: RCH2-OH + K2Cr2O7, special conditions  RCH=O RCH2-OH + C5H5NHCrO3Cl  RCH=O (pyridinium chlorochromate) [With other oxidizing agents, primary alcohols  RCOOH]

  21. Aldehyde synthesis: 2) oxidation of methylaromatics: Aromatic aldehydes only!

  22. Aldehyde synthesis: 3) reduction of acid chloride

  23. Ketone synthesis: 1) oxidation of secondary alcohols

  24. Ketone synthesis: 2) Friedel-Crafts acylation Aromatic ketones (phenones) only!

  25. Friedel Crafts acylation does not work on deactivated rings.

  26. Ketone synthesis: 3) coupling of RCOCl and R2CuLi

  27. Aldehydes, syntheses: • Oxidation of 1o alcohols • Oxidation of methylaromatics aromatic only • Reduction of acid chlorides • Ketones, syntheses: • Oxidation of 2o alcohols • Friedel-Crafts acylation aromatic only • Coupling of R2CuLi with acid chloride

  28. K2Cr2O7, special cond. or C5H5NHCrO3Cl 1o alcohol Ar-CH3 CrO3 H2O (AcO)2O aldehyde acid chloride LiAlH(O-t-Bu)3

  29. 2o alcohol NaOCl, etc. ketone acid chloride + ArH AlCl3 acid chloride + R2CuLi

  30. outline three different syntheses for benzaldehyde • outline three different syntheses for benzophenone • outline a different synthesis for each of the following compounds: • cyclohexanone, 4-bromobenzaldehyde, 2-pentanone, valeraldehyde, acetophenone, isobutyraldehyde,

  31. Synthesize benzaldehyde three different ways.

  32. Synthesize benzophenone three different ways.

  33. cyclohexanone, 4-bromobenzaldehyde, 2-pentanone, valeraldehyde, acetophenone, isobutyraldehyde, using a different method for each one.

  34. The methods could be reversed for the last two syntheses.

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