Lapworth

In one of the earliest mechanistic investigations m organic chemistry Arthur Lapworth discovered m 1904 that the rates of chlorination and brommation of acetone were the... 

Lapworth was far ahead of his time in understanding how organic reactions occur For an account of Lapworth s contributions to mechanistic organic chemistry seethe November 1972 issue of the Journal of Chemical Educa tion pp 750-752... 

Both parts of the Lapworth mechanism enol formation and enol halogenation are new to us Let s examine them m reverse order We can understand enol halogenation by analogy to halogen addition to alkenes An enol is a very reactive kind of alkene Its carbon-carbon double bond bears an electron releasing hydroxyl group which makes it electron rich and activates it toward attack by electrophiles... 

LAPWORTH (BENZOIN) Condensation Condensation of two molecules of aryl aldehydes fo an alpha-hydroxy ketone catalysed by CN (via cyanohydnns). 

Although the catalysis of the dimerization of aldehydes to acyloins by thiazolium ion has been known for some tlrae, the development of procedures using anhydrous solvents which give satisfactory yields of acyloins on a preparative scale was first realized in the submitters laboratories. The mechanism proposed by Breslow - for the thiazolium ion-catalyzed reactions is similar to the Lapworth mechanism for the benzoin condensation with a thiazolium ylide replacing the cyanide ion. Similar mechanisms are involved... 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or allyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propane tricarboxylic acid by oxidation of /3-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog. nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of oi-methyl-o -oxalosuccinic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-succinaldehyde dioxime from the ammonium salt of a-methyl-butyric acid by oxidation with. hydrogen peroxide from /9-methyllevulinic acid by oxidation with dilute nitric acid or hypobromite from /J-methyladipic acid and from the decomposition products of glyceric acid and pyruvic acid. The method described above is a modification of that of Higginbotham and Lapworth. ... 

In a study of the nitrosation of camphor-3-glyoxylic acid (89), Chorley and Lapworth isolated a compound whose structure (90) has recently been clarified by Hatfield and Huntsman. Decarboxylation and ring expansion occur and the reaction is rationalized in the sequence 89 90. The buttressing effect of a methyl group on... 

Arthur Lapworth (1872-1941) was born in Galashiels, Scotland, and received a D.Sc. at the City and Guilds Institute, London. He was professor of chemistry at the University of Manchester from 1909 until his retirement in 1937. 

Lapworth, Arthur, 707 Lard, composition of, 1062 Latex, rubber from, 245 vulcanization of, 245-246 Laurene, synthesis of, 875 Laurie acid, structure of, 1062 LDS0, 25 table of, 26... 

The idea that the properties of many organic compounds, especially the aromatic compounds, cannot be simply correlated with a single valence-bond structure, but require the assignment of a somewhat more complex electronic structure, was developed during the period 1923 to 1926 by a number of chemists, including Lowry, Lapworth, Robinson, and Ingold in England, Lucas... 

These ideas have arisen through the combined efforts of a large number of different workers, among whom may be mentioned Fry, Stieglitz, Lapworth, Lewis, Lucas, Lowry, Robinson, and especially Ingold. For details the reader is referred to the excellent review articles of the last named author.2... 

The addition is nucleophilic and the actual nucleophile is CN , so the reaction rate is increased by the addition of base. This was demonstrated by Lapworth in 1903, and consequently this was one of the first organic mechanisms to be known. The reaction has been carried out enantioselectively optically active cyanohydrins were prepared with the aid of optically active catalysts. ... 

The following is the accepted mechanism, which was originally proposed by Lapworth in 1903 ... 

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