Ald&ketonei

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: 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

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 4 3 2 1 C—C—C—C—C=O δ γ β α used 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. CH3CH2CH2CH=O butyraldehyde

CH3 CH3CHCH=O 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=O methanal

CH3CH=O ethanal

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 RCHO 1725 ArCHO 1700 R2CO 1710 ArCOR 1690 C—H stretch for aldehydes 2720 nmr:

-CHO 9-10 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: -4 CH4 alkane

oxidation -2 CH OH0 3

+2 H2C=O

HCO2+4 H

alcohol

aldehyde

carboxylic acid

reduction

CO2

Aldehydes, syntheses: 2. Oxidation of 1o alcohols 3. Oxidation of methylaromatics 4. Reduction of acid chlorides Ketones, syntheses: 7. Oxidation of 2o alcohols 8. Friedel-Crafts acylation 9. Coupling of R2CuLi with acid chloride

Aldehydes synthesis 1) oxidation of primary alcohols: RCH2-OH RCH2-OH

+

K2Cr2O7, special conditions

RCH=O

+ 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: 2. Oxidation of 1o alcohols 3. Oxidation of methylaromatics 4. Reduction of acid chlorides

aromatic only

Ketones, syntheses: 7. Oxidation of 2o alcohols 8. Friedel-Crafts acylation aromatic only 9. Coupling of R2CuLi with acid chloride

1o alcohol

Ar-CH3

acid chloride

K2Cr2O7, special cond. or C5H5NHCrO3Cl

CrO3 (AcO)2O

H2O

LiAlH(O-t-Bu)3

aldehyde

2o

alcohol

acid chloride + ArH

NaOCl, etc.

AlCl3

acid chloride + R2CuLi

ketone

1. outline three different syntheses for benzaldehyde 3. outline three different syntheses for benzophenone 5. outline a different synthesis for each of the following compounds: cyclohexanone, 4-bromobenzaldehyde, 2pentanone, 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.