Carboxylic acid ester hydrolyzes to form carboxylic acid

Reaction example

Reaction description: This reaction is the hydrolysis of carboxylic acid ester under alkaline conditions, and then acidic post-treatment to generate the corresponding carboxylic acid and alcohol.

reaction mechanism

A: Hydroxide ions attack the ester carbonyl group to form a tetrahedral intermediate

B: Under the promotion of oxygen anions, a methoxy group is eliminated to form the corresponding carboxylic acid.

C: Carboxylic acid removes its proton under alkaline conditions to form carboxylate

D: Acidification gives carboxylic acid

carboxylic acid

1Carboxylic acid forms a two-association body through hydrogen bonding, and its boiling point is higher than that of alcohols of similar molecular weight.

Comparison of the acidity of common acids: inorganic acid>carboxylic acid>carbonic acid>phenol>water>alcohol>alkyne.​

The acidity of carboxylic acid depends on the relative stability of the carboxylate anion (i.e. conjugate base) formed after ionization. The more stable the negative ion is, the more acidic the corresponding compound is.

Factors affecting the stability of negative ions

① The electronegativity of the central atom (the greater the electronegativity of the central atom, the stronger the ability to attract electrons and the greater the binding of electrons, the more stable the negative ions are, and the stronger the acidity of the compound.

For example, acidic H3C-H< H2N-H<HO-H< H-F)

②Atomic radius of the central atom (the larger the radius of the central atom, the better the dispersion of negative charges, the more stable the negative ions, and the stronger the acidity. For example, acidic HO-H< HS-H<HSe-H)

③Substituent (the acidity increases when it is connected with an electron-withdrawing group, and the acidity is weakened when it is connected with an electron-donating group)

④Hybridized state of the central atom (the electron pair of the negative ion is in the hybrid orbital with more s components, the closer it is to the nucleus, and the more bound it is to the nucleus, the more stable the negative ion is and the stronger the acidity. For example, acidity: acetylene > ethylene > ethane.)

⑤Type of solvent (Protic solvents have a solvation effect on negative ions, which is beneficial to the stability of negative ions and enhances acidity. For example, when there is a large group in the ortho position of the phenolic hydroxyl group, the solvation of oxygen negative ions will be hindered and the acidity will be weakened)

Effect of substituents on the acidity of carboxylic acids