halfapint (Ubiquitous Precursor Medal Winner)
05-05-02 07:49
No 305141
      Decarboxylating Benzoic  Bookmark   

Now JM of Advanced Organic Chemistry sez the way is to heat the aromatic acid with copper in quinoline. Copper I got, but doggone, my quinoline bucket is nigh empty. So if I spot any 2-amino-cinnamaldehyde I'll have a job for it. I get the feeling that activating substituents on the benzoic's ring would greatly help; it wouldn't get too difficult to come up with the m-sulfonate, I gather, and that would become a good leaving group if I wanted just plain benzene.

Heating the salt is what's in my old books for benzoic; I tried benzoic acid intimately mixed with 1 part (molecularly) sodium hydroxide and 1/2 part CaO, tried a couple times, didn't work. Got a few ml of dense orange oil that came over so hot, it might have been biphenyl, after a surprising amount of water.  Later I tried adding metallic copper and dry cupric sulfate to that same mix, and did a little better: got a bit of benzene, but not enough that it was worth the effort. Did spot one goof in the technique: using an open receiver, most of my condensed benzene may have evaporated during the course of the extended dry distillation.

In cleanup I noticed enough heat had been applied to soften the glassware, and in this way determined this wasn't the way to go either. The old book writers wouldn't all lie the same way, so I expect there exists a technique to recover benzene from some benzoic salt. It's just not going to happen in my glass. If a metal reaction vessel manifests itself, I might go on and stick some heat on its ass.

I thought it might bee a little easier than this. Has anyone any thoughts, some literary knowledge, or better yet experience getting benzene from benzoic acid?

Or, if that's too simple to answer, does anybody know any more about quinoline that's more specific than this?

Prepd. by the Skraup synthesis by heating aniline with glycerol and nitrobenzene in presence of sulfuric acid: Clarke, Davis, Org. Syn. coll. vol. I, 478 (2nd ed., 1941) 478;

alternate syntheses: Manske, Chem. Rev. 30, 113 (1942); Bergstrom, ibid. 35, 150 (1944).
Process based on the interaction of aniline with acetaldehyde and a formaldehyde hemiacetal: Cislak, Wheeler, U.S. pat. 3,020,281 (1962 to Reilly Tar and Chem.)

That includes BTW what any of these refs actually say...

a half a pints a half a pound a half a world a half a round
Sidearm n. Flask neck tube.
(Ubiquitous Precursor Medal Winner)
05-05-02 08:29
No 305147
(Rated as: excellent)

OK, Clarke, Davis, Org. Syn. coll. vol. I, 478 (2nd ed., 1941) 478

In a 5-l. round-bottomed flask, fitted with an efficient reflux condenser of wide bore, are placed, in the following order, 80 g. of powdered crystalline ferrous sulfate (Note 1), 865 g. (687 cc., 9.4 moles) of c.p. glycerol (Note 2), 218 g. (213 cc., 2.3 moles) of aniline, 170 g. (141 cc., 1.4 moles) of nitrobenzene, and 400 cc. of concentrated sulfuric acid (sp. gr. 1.84) (Note 3). The contents of the flask are well mixed and the mixture heated gently over a free flame. As soon as the liquid begins to boil, the flame is removed, since the heat evolved by the reaction is sufficient to keep the mixture boiling for one-half to one hour. If the reaction proceeds too violently at the beginning, the reflux condenser may be assisted by placing a wet towel over the upper part of the flask. When the boiling has ceased the heat is again applied and the mixture boiled for five hours. It is then allowed to cool to about 100 and transferred to a 12-l. flask; the 5-l. flask is rinsed out with a small quantity of water.

It goes on:

The 12-l. flask is then connected with the steam-distillation apparatus shown in Fig. 24, a 12-l. flask being used as a receiver (Note 4); steam is passed in (without external heat) until 1500 cc. has distilled (ten to thirty minutes). This removes all the unchanged nitrobenzene (1020 cc.). The current of steam is then interrupted, the receiver is changed, and 1.5 kg. of 40 per cent sodium hydroxide solution is added cautiously through the steam inlet. The heat of neutralization is sufficient to cause the liquids to boil and thus become thoroughly mixed. Steam is then passed in as rapidly as possible until all the quinoline has distilled. In this process, 68 l. of distillate is collected (two and one-half to three and one-half hours are required, unless a very efficient condensing apparatus is used, under which conditions the distillation may be complete in one-half to one and one-half hours). The distillate is allowed to cool, and the crude quinoline separated. The aqueous layer of the distillate is again distilled with steam until all the quinoline has been volatilized and collected in about 3 l. of distillate.

Shows some real neat glass, and then:

This 3 l. of distillate is then mixed with the first yield of quinoline, and 280 g. (150 cc.) of concentrated sulfuric acid is added. The solution is cooled to 05, and a saturated solution of sodium nitrite added until a distinct excess of nitrous acid is present (as shown either by starch-potassium iodide paper or by the odor). This generally requires 50 to 70 g. of sodium nitrite. The mixture is then warmed on a steam bath for one hour, or until active evolution of gas ceases, and is then distilled with steam until all the volatile material has been expelled (4 l. of distillate will result). The receiver is then changed and the mixture in the distillation flask is neutralized, as before, with 700 g. of 40 per cent sodium hydroxide solution. The quinoline is distilled exactly as described above, the aqueous portions of the distillate being distilled with steam until all the quinoline has been isolated. The crude product is then distilled under reduced pressure, and the fraction which boils at 110114/14 mm. is collected. The forerun is separated from any water which may be present, dried with a little solid alkali, and redistilled. The total yield is 255275 g. (8491 per cent of the theoretical amount based on the aniline taken) (Note 5).

a note:

1. In the Skraup synthesis of quinoline the principal difficulty has always been the violence with which the reaction generally takes place; it occasionally proceeds relatively smoothly, but in the majority of cases gets beyond control, with consequent loss of material through the condenser. By the addition of ferrous sulfate, which appears to function as an oxygen carrier, the reaction is extended over a longer period of time. It is thus possible to work with much larger quantities of material when ferrous sulfate is employed.

Finally, org-syn's alternates:

Quinoline can be prepared by heating a mixture of aniline, glycerol, and sulfuric acid1 alone or with an oxidizing agent like nitrobenzene,2 arsenic acid,3 ferric oxide,4 and vanadic acid.5 With the use of nitrobenzene, the reaction, according to the original method, takes place with extreme violence. The procedure followed here gives higher yields than those obtained with the ferric oxide method4 and is the most satisfactory for the preparation of quinoline, but its homologs are preferably prepared by the use of arsenic acid because of the somewhat greater yields. The violence of the original nitrobenzene method may also be moderated by the use of acetic6 or boric7 acid. Copper sulfate has been used as a catalyst in the Skraup synthesis,8 and the iron salt of m-nitrobenzenesulfonic acid has been employed as the oxidizing agent.9 Preliminary experiments on the boric acid method showed that the reaction runs smoothly but gives yields somewhat lower than those reported.7

Aniline all over the place, one of the things I wanted to make from my benzene. m-nitro benzoic acid might not bee too hard to come up with. Wonder if it would decarboxylate easier than benzoic acid. (Oh, that reminds me. I made some aniline the other day from benzoic acid, in polyphosphoric acid with nitromethane.)


US 3020281 is about running aniline and a mixture of methanol and formaldehyde mixed with either acetylene or acetaldehyde, over a catalytic bed of:
alumina, silica, silica-alumina, silica-magnesia, fuller's earth, pumice, zinc chloride, zinc fluoride, zinc phosphate, cadmium chromate, or cadmium fluoride at 450 to 500.

Is this running my own refs, too much like thinking out loud?

Recalling some do have library access, the org-syn refs:
1. Konigs, Ber. 13, 911 (1880); Skraup, Monatsh. 1, 316 (1880).
2. Skraup, Monatsh. 2, 139 (1881); Walter, J. prakt. Chem. (2) 49, 549 (1894).
3. Knueppel, Ber. 29, 704 (1896).
4. Barnett, Chem. News, 121, 205 (1920).
5. Darzens, Delaby, and Hiron, Bull. soc. chim. (4) 47, 227 (1930).
6. Cohn and Gustavson, J. Am. Chem. Soc. 50, 2709 (1928).
7. Cohn, ibid. 52, 3685 (1930).
8. Kirkhgof and Zasosov, Khim. Farm. Prom. 1934, No. 1, 40 [C. A. 28, 5454 (1934)].
9. Mikhailov, Novosti Tekhniki, No. 34, 51 (1940) [C. A. 34, 5847 (1940)].
but it would bee so handy, to spot a jug of o-amino cinnamaldehyde.

a half a pints a half a pound a half a world a half a round
Demimonde, n. Half a world