[497-19-8] · CNa2O3 · Sodium Carbonate · (MW 105.99)
(widely used base)
Physical Data: mp 851 °C; d 2.532 g cm-3.
Solubility: sol glycerol, water.
Form Supplied in: white powder.
Handling, Storage, and Precautions: moderately toxic; severe irritant; noncombustible; stable; decomposition occurs slowly above 400 °C to give carbon dioxide and sodium oxide; incompatible with strong acids and aluminum; hygroscopic.
Cyanoethylated b-keto esters can be hydrolyzed with aqueous sodium carbonate to the corresponding d-keto nitrile (eq 1).1 The use of sodium hydroxide in this reaction leads to hydrolysis of the nitrile, affording the keto acid.
The selective hydrolysis of esters in the presence of acetyl-protected amines can be achieved with aqueous sodium carbonate (eq 2).2
The decomposition of sulfonylhydrazines to aldehydes was achieved using sodium carbonate as base. The sulfonylhydrazine was heated in ethylene glycol to 150 °C, and 4-6 equiv of sodium carbonate added. The reaction is complete in approximately 30 s. This reaction has been applied to the formation of aromatic,3 heterocyclic,3 and aliphatic aldehydes (eq 3).4
The reaction of b-keto esters with a,b-unsaturated aldehydes in the presence of sodium carbonate and a phase-transfer catalyst afforded the Michael addition product (eq 4).5 The use of sodium hydroxide in this reaction led to substantial decomposition.
This methodology was used to prepare 3-oxo-5-phenyl-1-cyclohexene from ethyl acetoacetate and cinnamic acid (eq 5).5 Under the same conditions, b-cyano esters and a,b-unsaturated aldehydes undergo Knoevenagel condensation (eq 6).5
Sodium carbonate is an effective acid scavenger for hydrogenations. The hydrogenation of m-nitro-O-benzoylmandelate with Raney Nickel and sodium carbonate in ethanol at 180 °C afforded the ethyl ester of m-aminophenylacetic acid (eq 7).6 Other bases were found to be less effective in removing the benzoic acid, resulting in slow and incomplete reactions. Sodium carbonate is also used in the sodium hydrophosphite hydrogenations of many functional groups.7
b-Diketones react with (Diacetoxyiodo)benzene in the presence of sodium carbonate to afford phenyliodonium b-diketonates (eq 8).8 Ozonolysis of the phenyliodonium b-diketonates provides an efficient synthesis of triketones.
Sodium carbonate is used in the alkylation of amines,9 debromination,10 hydrolysis,11 imidazoline synthesis,12 as a buffer,13 and a neutralization agent.14
Giba-Geigy, Summit, NJ, USA