Sodium cinnamate, production

Cinnamic acid is usually prepared by Perkin s reaction, benzaldehyde being heated with sodium acetate in the presence of acetic anhydride. It is probable that the benzaldehyde and the acetic anhydride combine under the catalytic action of the sodium acetate, and the product then readily loses water to give mono-benzylidene acetic anhydride (. ). The latter, when subsequently... 

The mi.xtuie of benzaldehyde, sodium acetate, and acetic anhydride is heated to 180 m a sir.all round flask with upright condenser in an oil-bath for about eight houis. The mass is poured out whilst hot into a large round flask (i litre), sodium carbonate added until alkaline, and any unchanged benzaldehyde distilled off with steam. After filtering from undissolved resinous by-products, hydrochloric acid is added, which precipitates the free cinnamic acid in white crystalline flakes. It may be purified by recrystallisation from hot water. Yield, 15—20 grams. 

The addition of stabilized nucleophiles to activated ir-systems is one of the oldest and most useful constructive methods in organic synthesis, dating back more than a hundred years. In 1887 Michael, after whom the most well-known example of this reaction was named, published the first of a series of papers on this reaction describing the addition of the sodium salt of both diethyl malonate (1) and ethyl ace-toacetate (2) to ethyl cinnamate (3) to give the products (4) and (5), respectively (equation 1).1 This Mi-... 

Grignard solution is added dropwise over a period of 40-50 min, so that the temperature of the reaction mixture remains below -60°C. The addition funnel is removed from the setup, with the septum/nitrogen inlet connected directly to the flask. After the cold mixture is stirred for 15 min more, ethyl cinnamate (10.32 g, 0.0586 mol) (Note 7) is added via syringe over a 2-3 min period. Stirring is continued as the flask is allowed to warm slowly to room temperature (Note 8). The off-white to beige reaction mixture is cooled to <5°C (ice-water bath) and quenched by the portion-wise addition of chilled 1 M hydrochloric acid (200 mL), so that the internal temperature remains below 20°C (Note 9). The layers are separated, and the aqueous phase is extracted twice with ethyl ether (100 mL each). The combined organic layers are washed with saturated sodium bicarbonate solution (Note 10), dried over sodium sulfate, and the solvents are removed at a rotary evaporator (25°C/60 mm). The residual oil is transferred to a 100-mL, round-bottomed flask and distilled bulb-to-bulb (Note 11). The product (9.69-9.85 g. 76.5-78%) (Note 12) is collected at an air bath temperature of 110-112°C, 0.20 mm. 

In a 200-cc. round-bottom flask, fitted with a reflux condenser, are placed 50 g. (0.33 mole) of m-nitrobenzaldehyde (Note 1), 40 g. (0.48 mole) of freshly fused sodium acetate, and 70 g. (0.68 mole) of acetic anhydride. The contents of the flask are well mixed and the mixture heated in an oil bath held at 1800 for about thirteen hours. After the reaction product has been allowed to cool slightly, it is poured into 200-300 cc. of water and then filtered by suction (Note 2). After the solid has been washed several times with water, it is dissolved in a solution of 20 cc. of ammonium hydroxide (sp. gr. 0.9) in about 200 cc. of water. The solution of the ammonium salt, after filtering, is poured into a solution of 15 cc. of sulfuric acid (sp. gr. 1.84) in about 200 cc. of water (Note 3). The precipitated m-nitro-cinnamic acid is filtered, redissolved in ammonium hydroxide, and again precipitated by pouring the solution into dilute sulfuric acid (Note 4). 

A hot solution of sodium ethoxide is prepared, in a 3-1. round-bottomed flask, from 46 g. (2 gram atoms) of sodium and 1.6 1. of absolute ethyl alcohol. With shaking, a solution of 139 g. (2 moles) of hydroxylamine hydrochloride in 100 cc. of hot water is added. The resulting suspension is cooled Quickly by placing the flask in an ice-water mixture and is then filtered with suction through a Buchner funnel. The residue of sodium chloride is washed with small portions (total 200 cc.) of absolute ethyl alcohol. The filtrate is returned to the 3-1. flask, and to it is added 148 g. (1 mole) of cinnamic acid, whereupon a voluminous precipitate forms. The mixture is refluxed on a steam bath for nine hours (Note 1). The amino acid begins to separate after five to six hours the suspended solid causes the mixture to bump (Note 2). The suspension is allowed to remain overnight at room temperature, and the crystals are then collected on a Buchner funnel (Note 3). The product is washed with 300 cc. of absolute ethyl alcohol, then with some ice-cold water to remove all the sodium chloride, and finally with 300 cc. of absolute ethyl alcohol, always in small portions. The colorless crystals of amino acid are dried in a vacuum desiccator over flake sodium hydroxide. The yield is 56 g. (34 per cent of the theoretical amount). 

In the mercuration of cinnamic acid and its esters, CsHg.CHg.CHa. CO OH, the mercury residue always attaches itself to the a-carbon atom, and the solvent takes part in the reaction, attacking the -carbon atom, alkyloxy groups becoming linked to the latter (I.). When the mercurated esters are saponified by sodium hydroxide, and the resulting product treated with sulphuric acid, water is eliminated between the hydroxy-mercuri and carboxyl groups, and an anhydride results (II,). 

Benzalacetone has been obtained in small yield by drv distillation of a mixture of calcium acetate and calcium cinnamate (1) by heating the sodium derivative of cinnamaldehyde with methyl iodide (2) by heating cinnamaldehyde and methyl alcohol with zinc chloride (2) by heating acetone and benzaldehyde with acetic anhydride or zinc chloride (3). It is also formed when styrene and acetyl chloride are condensed by means of stannic chloride and the product is treated with diethylaniline (4) and when the vapors of cinnamic acid and acetic acid are passed together over ferric oxide at 470-490° (5). The only practical method, however, consists in condensing benzaldehyde and acetone by means of dilute aqueous alkali (6). 

A hot solution of 2 moles of hydroxylamine hydrochloride in 100 ml. of hot water is added to a hot solution prepared from 2 gram atoms of sodium and 1.61. of absolute ethanol and, after cooling, the sodium chloride formed is removed by suction filtration. Addition of 1 mole of cinnamic acid produces a voluminous precipitate of (2), which dissolves at the reflux temperature. After 5-6 hrs. the amino acid (3) begins to separate and in 9 hrs. the reaction is complete. The crystallized product is washed alternately with water to remove sodium chloride and with absolute alcohol for drying. 

---