HCCH + CO + H2O → CH2=CHCO2H
|Ozonolysis of Alkenes|
Reaction type: Electrophilic Addition
• Overall alteration: C=C to 2 x C=O
• Ozonolysis suggests that ozone will cause the alkene to break (-lysis)
• Reagents used: ozone followed by:
o a reducing work-up, either Zn in dimethyl sulfide (CH3)2S or acetic acid
o an oxidizing work-up, typically H2O2
• It is suitable to understanding the process as cleaving the alkene into two carbonyls
o The substituents on the C=O rely on the substituents on the original C=C.
o The work-up regulates the oxidation state of the produces
|Carbonation of Grignards|
The reaction usually in Et2O or THF followed by H3O+ work-up
Type of reaction: Nucleophilic Addition
Grignard reagents react with dry ice (solid CO2) followed by aqueous acid work-up to produced carboxylic acids.
Carbon dioxide CO2 can be thought of as a being a di-carbonyl compound: O=C=O
Remember that the carboxylic acid has one extra C molecules compared to the original halide from which the Grignard reagent was made.
Oxidation of 1o Alcohols
|Type of reaction: Oxidation-reduction|
Primary alcohols1o, RCH2OH, can be oxidized to carboxylic acids, RCO2H, under aqueous conditions.
Usual reagents are based on aqueous Cr (VI):
Chromate salts, e.g. Na2CrO4, chromic acid, H2CrO4, dichromate salts, e.g. K2Cr2O7
The oxidation goes first to the aldehyde followed by the carboxylic acid.
R can be alkyl or aryl.
Oxidation of Aldehydes
Type of reaction: Oxidation-reduction
Aldehydes, RCHO, oxidized to carboxylic acids, RCO2H, under aqueous conditions.
Usual reagents are based on aqueous
Crchromic acid, H2CrO4, chromate salts, e.g. Na2CrO4
The oxidation essentially proceeds on the hydrate, RCH(OH)2, is formed by the reaction of water with the aldehyde.
R can be aryl or alkyl
Oxidation of Alkyl Benzene
Type of reaction: Oxidation
When reacted under strongly oxidizing conditions, benzylic-H are oxidized all the way to the carboxylic acid.
Basic reagents: Hot, acidic KMnO4
The alkyl substituent can be methyl-, primary 1o or secondary 2o alkyl.3o alkyl is not oxidized because they lack a benzylic-H.
Simple alkane C-H cannot be oxidized in this manner.
This gives a potential route to aromatic carboxylic acids
|2500 - 3500 (very wide)||OH stretch|
|10 -12 (exchangeable)||-COOH proton|
|2 – 3||H-C-COOH|