Oxalates, methyl

Note. Methyl oxalate, unlike most other esters, hydrolyses very rapidly in aqueous solution hence it will evolve CO in the above test, owing to the formation of methanol and free oxalic acid. 

Most are very sparingly soluble in water note however that methyl formate, methyl oxalate, methyl succinate, methyl and ethyl tartrate, methyl and ethyl citrate are soluble in water. 

Hydrolysis. Place 2 ml. of the ester in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, or use the reflux-distillation apparatus shown in Fig. 38, p. 63. Add about 20 ml. of 10% aqueous NaOH solution, and some fragments of unglazed porcelain, and reflux gently for 20-30 minutes. (Note that methyl oxalate is hydrolysed rapidly by water alone. Phenyl esters on the other hand hydrolyse comparatively slowly even with hot NaOH solution, and should be heated... 

Hydrolysis of methyl oxalate. The exceptionally rapid hydrolysis of rnethyl oxalate can be followed thus Dissolve 0 2 g. of finely powdered methyl oxalate in 10 ml. of water, and add i drop of phenolphthalein. Then add very dil. NaOH solution (1%) drop by drop until the solution just turns pink it will be noticed that the colour rapidly fades, but is restored on the Further addition of 1-2 drops of NaOH solution. The colour fades again and the addition can be repeated until hydrolysis is complete. Oxalic acid (with which methyl oxalate may be confused) gives a precise end-point when treated with NaOH solution in this way. 

Dissolve 0 2 g. of methyl oxalate in 10 ml. of water, add without delay 1 ml. of ammonia (d, o 88o) and shake a fine white precipitate of the insoluble oxamide is produced. A precipitate of oxamide is similarly produced when 2-3 drops of ammonia are added directly to 0 5 ml. of ethyl oxalate. 

Ethyl oxalate is the only liquid ester which gives this rapid separation of the amide, which is therefore characteristic. Methyl and ethyl formate react rapidly with ammonia, but the soluble formamide does not separate methyl succinate gives crystalline succinamide after about I hour s standing, other esters only after a much longer time. The solid esters, other than methyl oxalate, are either soluble in water and remain so when treated with ammonia, or alternatively are insoluble in water and hence clearly not methyl oxalate. 

COj liberated. All acids esters which hydrolyse easily, e.g., methyl oxalate (p. 357) salts of amines nitrophenols. 

Of the common esters, methyl oxalate (solid, m.p. 54°) and ethyl oxalate (liquid) give amides almost immediately upon shaking with concentrated ammonia solution. The resulting oxamide, m.p. 417°, is valueless as a derivative. The esters may, however, be easily hydrolysed and identified as above. 

Methyl oxalate (p. loi) Cet l palmitate (Spermaceti). .. Myricyl palmitate (Bees... 

Methyl malonatc, 13, 100 Methyl 0-naphthyl ketone, 17, 65 Methyl nitrite, 16, 44 Methyl oxalate, 10, 70 3-Methylpentanoic acid, 11, 76 Methyl 0-phenylethyl ketone, 16, 49... 

Methylene bromide, 112 Methyl ethyl ketone, 23 a-Methyl d-glucoside, 112 Methyl Oxalate, 70 Myristyl alcohol, 64... 

The methanol used is the commercial (almost acetone-free) grade known as Columbian Spirits. This material is redistilled for recrystallizing the methyl oxalate. 

Methyl oxalate has been prepared by distilling a mixture of oxalic acid, methyl alcohol and sulfuric acid 1 by dissolving anhydrous oxalic acid in hot methyl alcohol 2 by esterifying oxalic acid with methyl alcohol, using anhydrous hydrogen... 

Several total syntheses of antirhine (11) and 18,19-dihydroantirhine (14) have been developed during the last decade. Wenkert et al. (136) employed a facile route to ( )-18,19-dihydroantirhine, using lactone 196 as a key building block. Base-catalyzed condensation of methyl 4-methylnicotinate (193) with methyl oxalate, followed by hydrolysis, oxidative decarboxylation with alkaline hydrogen peroxide, and final esterification, resulted in methyl 4-(methoxycar-bonylmethyl)nicotinate (194). Condensation of 194 with acetaldehyde and subsequent reduction afforded nicotinic ester derivative 195, which was reduced with lithium aluminum hydride, and the diol product obtained was oxidized with manganese dioxide to yield the desired lactone 196. Alkylation of 196 with tryptophyl bromide (197) resulted in a pyridinium salt whose catalytic reduction... 

Figure 3. Methyl group of methyl oxalate was derived from methoxyl group of the B-ring of >3-0-4 lignin model dimer 1-D.

Only a few of such reactions of these rings have been reported since CHEC-II(1996). However, Weaver and Tennant <1999TL8157, 2000TL9319> have demonstrated that imidazo[4,5-f]isoxazoles such as 19 undergo thermally driven reactions with acetylenic diesters (such as 22) to yield, rather than the expected bridged bicyclic compound 20 or the pyridine Woxide 21, the 2-pyrrol-2-ylimidazole 24 which the authors suggest proceeds via loss of a methyl oxalate unit. The proposed pathway is outlined in Scheme 1. 

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