Aldehydes and Ketones
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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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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:

R-COOH, R-CO2H,

Common names:

HCO2Hformic acidL. formica ant

CH3CO2Hacetic acidL. acetum vinegar

CH3CH2CO2Hpropionic acidG. “first salt”

CH3CH2CH2CO2Hbutyric acidL. butyrum butter

CH3CH2CH2CH2CO2Hvaleric acidL. valerans


Carboxylic acids, common names:

CH3(CH2)4CO2Hcaproic acidL. caper goat

CH3(CH2)5CO2H---

CH3(CH2)6CO2Hcaprylic acid

CH3(CH2)7CO2H---

CH3(CH2)8CO2Hcapric acid

CH3(CH2)9CO2H---

CH3(CH2)10CO2Hlauric acidoil of lauryl


5 4 3 2 1

C—C—C—C—C=O

δ γ β αused in common names


Special names!


ALDEHYDES AND KETONES

“carbonyl” functional group:

Aldehydes Ketones


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)


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=OCH3CH=O

methanalethanal


Ketones, common names:

Special name:acetone

“alkyl alkyl ketone” or “dialkyl ketone”


(o)phenones:

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


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.


Physical properties:

polar, no hydrogen bonding

mp/bp are relatively moderate for covalent substances

water insoluble

(except: four-carbons or less)


Spectroscopy:

IR:C=O stretch, strong ~1700 cm-1

RCHO1725ArCHO1700

R2CO1710ArCOR1690

C—H stretch for aldehydes2720

nmr: -CHO9-10 ppm


acetophenone

C=O

stretch


valeraldehyde

CHO

C—H

stretch

2720 cm-1

C=O stretch


valeraldehyde

CH3CH2CH2CH2CH=O

a b c d e

-CHO


Oxidation/Reduction:

oxidation numbers:

oxidation

-4 -2 0 +2 +4

CH4 CH3OH H2C=O HCO2H CO2

alkane alcohol aldehyde carboxylic acid

reduction


  • 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


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]


Aldehyde synthesis: 2) oxidation of methylaromatics:

Aromatic aldehydes only!


Aldehyde synthesis: 3) reduction of acid chloride


Ketone synthesis: 1) oxidation of secondary alcohols


Ketone synthesis: 2) Friedel-Crafts acylation

Aromatic ketones (phenones) only!


Friedel Crafts acylation does not work on deactivated rings.


Ketone synthesis: 3) coupling of RCOCl and R2CuLi


  • 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


K2Cr2O7, special cond.

or C5H5NHCrO3Cl

1o alcohol

Ar-CH3

CrO3 H2O

(AcO)2O

aldehyde

acid chloride

LiAlH(O-t-Bu)3


2o alcohol

NaOCl, etc.

ketone

acid chloride + ArH

AlCl3

acid chloride + R2CuLi


  • 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,


Synthesize benzaldehyde three different ways.


Synthesize benzophenone three different ways.


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


The methods could be reversed for the last two syntheses.


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