Ethanol, absolute, preparation mechanism

Solution in ethanol. For preparation of 6-10% solutions of the ethoxide in absolute ethanol, investigators conventionally add sodium to the alcohol in lumps or slices, with or without mechanical stirring, with or without a nitrogen atmosphere, and cool or heat as required until the metal is dissolved. Commercial anhydrous ethanol now available is satisfactory. A glycerol-sealed stirrer has been used, also a magnetic stirrer. The hydrogen liberated should be vented into a hood. Two inverse procedures are described below the second is shorter. 

E. Quench and purification. While the butyllithium addition is taking place, an acidic ethanol quench solution is prepared in a 3-L, two-necked, round-bottomed flask, equipped with a mechanical stirrer and a 250-mL, pressure-equalizing dropping funnel. The flask is charged with 1 L of absolute ethanol and the funnel with 250 mL of acetyl chloride. The ethanol is stirred rapidly and the flask is cooled with an ice bath as the acetyl chloride is added over a 30-40-min period and then the cooling bath is removed and stirring is continued for 20-30 min. After the main reaction mixture has been stirred for 30 min at room temperature, it is cooled with a dry ice-acetone bath. The acidic ethanol solution is cooled with an ice bath and the cold, main reaction mixture is quenched by addition (via a double-ended needle) into the rapidly stirred, cold, acidic ethanol solution over a 3 to 3.5 hr period (Note 16). 

A solution of sodium ethoxide is prepared under nitrogen from 70 g. (3.04 gram atoms) of sodium and 2-1. of absolute ethanol (Note 1) in a 3-1. three-necked flask which is equipped with mechanical stirrer, efficient reflux condenser, dropping funnel, and a thermometer which dips below the level of the liquid in the flask. Chloropicrin (100 g., 0.61 mole) (Note 2) is placed in the dropping funnel, and the stirred solution is heated to 58-60° with a water bath. The chloropicrin is added at a rate of 30-35 drops per minute until the reaction becomes self-sustaining (about 20 minutes), at which point the water bath is removed and the balance of the chloropicrin is added at a rate sufficient to maintain the temperature at 58-60° (Note 3). When the addition, which requires nearly 2 hours, is complete, the stirrer is stopped and the mixture is allowed to stand overnight. 

Reactivity of (HPS)VO(OH). A variety of coordination complexes catalyze the oxidation of bromide by hydrogen peroxide. The first and most studied catalyst is the hydroxooxovanadium(V) complex of hydrox-yphenylsalicylideneamine (H2HPS, shown in Figure 4) (35). The proposed mechanism is shown in Scheme 3. The catalyst precursor is the crystalline (HPS)VO(OEt)(EtOH) compound, which is readily prepared from VO(iOPr)3 and H2HPS (36) in absolute ethanol. Dissolution of this solid in N,N-dimethylformamide (DMF) gives rise to five species (HPS)VO(OEt), the active catalyst (HPS)VO(OH), and three stereochemically distinct di-... 

Ethoxyethylperoxyls were prepared by a variety of methods and react to give ethyl acetate, ethanol, acetaldehyde and ethyl formate. (Table V). There was no evidence for the formation of di-(1-ethoxyethyl) peroxide, a result that is not entirely incompatible with Diaper s work in view of the large difference in the size the peroxy radicals studied by the two groups of workers. The absolute yields of the products were difficult to ascertain with any degree of certainty because of secondary reactions. The high yield of ethyl formate is, however, diagnostic for the intermediacy of alkoxy radicals and indicates that at least 20 of the self-reactions of 1-ethoxyethylperoxyls occur via the radical mechanism. 

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