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Acting as a nucleophile, the carbanion attacks the carboxyl carbon of a second molecule of ester.ģ.

An α hydrogen on the ester is removed by a base, which leads to the formation of a carbanion that is resonance stabilized.Ģ. The Claisen condensation reaction occurs by a nucleophilic addition to an ester carboxyl group, which follows these steps:ġ. Upon heating, the β ketoacid becomes unstable and decarboxylates, leading to the formation of the methyl ketone.Ī Claisen condensation of ethyl acetate prepares acetoacetic ester. Concentrated sodium hydroxide is strong enough to hydrolyze both the ester functional group and the ketone functional group and, therefore, forms the substituted acid rather than the ketone.Ī reaction between a disubstituted acetoacetic ester and dilute sodium hydroxide forms the following products:

This ketone occurs because dilute sodium hydroxide has sufficient strength to hydrolyze the ester functional group but insufficient strength to hydrolyze the ketone functional group. If dilute sodium hydroxide were used instead of concentrated, the product formed would be a methyl ketone. The acid formed has a methyl and an ethyl group in place of two hydrogens of acetic acid and is therefore often referred to as a disubstituted acetic acid. Hydrolysis using concentrated aqueous sodium hydroxide leads to the formation of the sodium salt of the disubstituted acid.Īddition of aqueous acid liberates the disubstituted acid. This carbanion can participate in a typical S N reaction, allowing the placement of a second alkyl group on the chain. To accomplish this conversion, the reaction product in step 2 above would be reacted with a very strong base to create a carbanion. The second hydrogen on the methylene unit of acetoacetic ester can also be replaced by an alkyl group, creating a disubstituted acid. Hydrolysis of the resulting product with concentrated sodium hydroxide solution liberates the sodium salt of the substituted acid.Īddition of aqueous acid liberates the substituted acid. The resulting carbanions can participate in typical S N reactions that allow the placement of alkyl groups on the chain. Either or both of these hydrogens can be removed by reaction with strong bases. The hydrogens on the methylene unit located between the two carbonyl functional groups are acidic due to the electron withdrawing effects of the carbonyl groups. Synthesis of substituted acetic acids via acetoacetic esterĪcetoacetic ester, an ester formed by the self‐condensation of ethyl acetate via a Claisen condensation, has the following structure: Grignard reagents react with carbon dioxide to yield acid salts, which, upon acidification, produce carboxylic acids. An electron pair on one of the oxygens displaces the ammonium group from the molecule. A water molecule is attracted to the carbocation.ĩ. The amide is protonated by the acid, forming a carbocation.Ħ. The enol tautomerizes to the more stable keto form.ĥ. The oxonium ion loses a proton to the nitrogen atom, forming an enol.Ĥ. The carbocation generated in Step 1 attracts a water molecule.ģ. The nitrogen atom of the nitrile group is protonated.Ģ. The mechanism for these reactions involves the formation of an amide followed by hydrolysis of the amide to the acid. These hydrolysis reactions can take place in either acidic or basic solutions. The hydrolysis of nitriles, which are organic molecules containing a cyano group, leads to carboxylic acid formation. In the above example, t‐butylbenzene does not contain a benzylic hydrogen and therefore doesn't undergo oxidation. Remember: Mild oxidizing agents such as manganese dioxide (MnO 2) and Tollen's reagent are only strong enough to oxidize alcohols to aldehydes.Īlkyl groups that contain benzylic hydrogens-hydrogen(s) on a carbon α to a benzene ring-undergo oxidation to acids with strong oxidizing agents. All strong oxidizing agents (potassium permanganate, potassium dichromate, and chromium trioxide) can easily oxidize the aldehydes that are formed. The oxidation of primary alcohols leads to the formation of alde‐hydes that undergo further oxidation to yield acids. The oxidation of primary alcohols and aldehydes The ozonolysis of alkenes produces aldehydes that can easily be further oxidized to acids.