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
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.
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)10CO2Hlauric acidoil of lauryl
5 4 3 2 1
δ γ β αused in common names
ALDEHYDES AND KETONES
“carbonyl” functional group:
Aldehydes, common names:
Derived from the common names of carboxylic acids;
drop –ic acid suffix and add –aldehyde.
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.)
Ketones, common names:
“alkyl alkyl ketone” or “dialkyl ketone”
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.
polar, no hydrogen bonding
mp/bp are relatively moderate for covalent substances
(except: four-carbons or less)
IR:C=O stretch, strong ~1700 cm-1
C—H stretch for aldehydes2720
nmr: -CHO9-10 ppm
a b c d e
-4 -2 0 +2 +4
CH4 CH3OH H2C=O HCO2H CO2
alkane alcohol aldehyde carboxylic acid
Aldehydes synthesis 1) oxidation of primary alcohols:
RCH2-OH + K2Cr2O7, special conditions RCH=O
RCH2-OH + C5H5NHCrO3Cl RCH=O
[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
K2Cr2O7, special cond.
acid chloride + ArH
acid chloride + R2CuLi
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.