Kolbe’s synthesis

Nevertheless, the vitalists were not easily convinced, and it took a few decades before the vis vitalis theory was finally laid to rest. The final nail in its coffin may have been provided by Kolbe s synthesis of acetic acid from its constituent elements in 1845 (Kolbe, 1845). 

The first stage of Kolbe s synthesis is analogous to the well-known aliphatic synthesis of alkyl carbonates from alkoxides and carbon dioxide ... 

Since, in Kolbe s synthesis, as here described, the mono-sodium salicylate reacts to some extent with unchanged sodium phenoxide, producing the di-sodium salt, part of the phenol is liberated and excluded from the reaction. The reaction proceeds to completion if the sodium phenoxide is heated to about 150° for a long time, with carbon dioxide under pressure in the autoclave. This is the technical method of Schmitt. 

Sandmeyer s synthesis of aromatic nitriles is far more elegant than the removal of water from the ammonium salts of carboxylic acids, which latter reaction is also applicable to benzene derivatives. In particular, the former synthesis permits of the preparation of carboxylic acids via the nitriles, and so provides a complete substitute for Kolbe s synthesis (alkyl halide and potassium cyanide), which is inapplicable to aromatic compounds. The simplest example is the conversion of aniline into benzoic add. The converse transformation is Hofmann s degradation (benzamide aniline, see p. 152). 

This is Kolbe s synthesis of phenolic acids. It is capable of very wide application. In all cases the carboxyl group primarily seeks the or o-position if that is occupied, some condensation in the para-position occurs. The following are some examples. 

In connection with his investigation of ketonic acids, Hofer 3 has used the electrosynthetic reaction, previously discovered with Miller,4 which consists in electrolyzing potassium salts of organic acids in mixture with potassium acetate and other lower fatty acids. The general nature of the reaction is that the two anions unite, as in Kolbe s synthesis, carbonic acid being split off, e.g.,... 

Salicylic acid is manufactured by what is known as Kolbe s synthesis, which consists in heating the sodium salt of phenol with carbon dioxide under pressure at 130°. The steps involved in the reaction are those indicated below —... 

In 1845, for instance, Adolph Wilhelm Hermann Kolbe (1818-84), a pupil of Wohler s, succeeded in synthesizing acetic acid, an indubitably organic substance. Furthermore, he synthesized it by a method which showed that a clear line of chemical change could be drawn from the constituent elements, carbon, hydrogen, and oxygen, to the final product, acetic acid. This synthesis from the elements or total synthesis is all that can be asked of the chemist. If Wohler s synthesis of urea did not settle the matter of the vital force, Kolbe s synthesis of acetic acid did. 

Wohler s synthesis of urea (1828) and Kolbe s synthesis of acetic acid (1845) moved from the scientific scene s vis vitalis theory. Kolbe synthesis is presented here because of its historical importance and also as an extraordinary introduction to the ecological issues of industrial organic synthesis (Scheme 1.16). 

In this way, the operational range of the Kolbe-Schmitt synthesis using resorcinol with water as solvent to give 2,4-dihydroxy benzoic acid was extended by about 120°C to 220°C, as compared to a standard batch protocol under reflux conditions (100°C) [18], The yields were at best close to 40% (160°C 40 bar 500 ml h 56 s) at full conversion, which approaches good practice in a laboratory-scale flask. Compared to the latter, the 120°C-higher microreactor operation results in a 130-fold decrease in reaction time and a 440-fold increase in space-time yield. The use of still higher temperatures, however, is limited by the increasing decarboxylation of the product, which was monitored at various residence times (t). 

C Griehl, A Kolbe, S Merkel. Quantitative description of epimerization pathways using the carbodiimide method in the synthesis of peptides. J Chem Soc Perkin Trans 2 2525, 1996. 

These syntlieses give no indication as to the structure of aspartic acid, the constitutional formula of which is based upon Kolbe s work, that it is amino-succinic acid the only synthesis of aspartic acid which confirms this constitution appears to be that by Piutti in 1887. Sodium oxalacetic ester, prepared from oxalic ester and acetic ester in the presence of sodium ethylate —... 

Another example of a Kolbe dimerization reaction is found in Corey s synthesis of a-onoceradiene (14), y6-onceradiene (15) and (+)-pentacyclosqualene (16) each is derived from either the ammonium salt 18, or the acetoxy ammonium salt derived in situ from 20 in the manner portrayed in Eqs. (4) and (5) [6,7]. 

A modification of the Kolbe synthesis which permits the immediate conversion of all the phenol into salicylic acid is known as Schmitt s synthesis. According to this method, as in the other, the sodium phenyl carbonate is first prepared this is then further heated in an... 

Until recently there were few cases in which an alkali nitrite could replace silver nitrite in the synthesis of nitro compounds. Such a case was Kolbe s nitroalkane synthesis, in which an alkali salt of a 2-haloalkanoic acid was treated with a boiling aqueous solution of an alkali nitrite the 2-nitroalkanoic acid formed lost carbon dioxide under the reaction conditions and the nitroalkane distilled over in the steam. The Kolbe synthesis is, however, of practical use only for the preparation of nitromethane (38% yield from chloro-acetic acid648) and nitroethane (about 50% yield from 2-bromopropionic acid649) it is substantially valueless for higher fatty acids.649,650... 

Charles Friedel (Strasbourg, 12 March 1832-Montauban, 20 April 1899) was (1876) professor of mineralogy in the Sorbonne and succeeded Wurtz as professor of organic chemistry in the Sorbonne (1884-99). With James Mason Crafts (Boston, 1839-Ridgefield, Conn., 20 June 1917), professor in and later president of the Massachusetts Institute of Technology, he discovered the use of aluminium chloride in reactions of synthesis, e.g. of homologues of benzene. Friedel prepared a number of artificial minerals (quartz, tridymite, rutile, etc.), often in collaboration with Edmund Sarasin, from 1879. FriedeFs discovery of secondary propyl alcohoF verified Kolbe s prediction of its... 

Curtius began work at Kolbe s suggestion on Dessaignes synthesis of hippuric acid (see p. 315) and at Baeyer s suggestion in Munich he used the ethyl ester of glycocoll, which he prepared. By the action of hydrochloric acid and sodium nitrite on this he discovered diazoacetic ester, the first aliphatic diazo-compound. He discovered hydrazine by the action of hot dilute acids on what he supposed was triazoacetic acid C3H3Ne(COOH)3, the sodium salt of which he obtained by the action of concentrated sodium hydroxide on diazoacetic ester.The starting material was later shown to be bisdiazoacetic... 

Regnault who synthesized vinyl chloride in 1835 was considered by Liebig to be one of the most talented students at Ecole Polytechnic in Paris. Regnault s synthesis, which was used commercially a century later, was based on the dehydrochlorination of the "oil of the Dutch chemists" (Dieman, Trotswyck, Bondt and Laurverenburgh) which was first produced in 1795, by the addition of chlorine to "olefiant gas". Kolbe used the term vinyl radical in 1854 and the term vinyl chloride was used without controversy in the 1860 s. 

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