Trichloromethane, hydrolysis

Trapping of intermediates (contd.) carbenes, 50,267 dienones, 356 internal, 266 peroxyzwitterions, 193 Trichloromethane hydrolysis, 42, 267 T riphenylmethane acidity, 271... 

The amount of residual sulfonate ester remaining after hydrolysis can be determined by a procedure proposed by Martinsson and Nilsson [129], similar to that used to determine total residual saponifiables in neutral oils. Neutrals, including alkanes, alkenes, secondary alcohols, and sultones, as well as the sulfonate esters in the AOS, are isolated by extraction from an aqueous alcoholic solution with petroleum ether. The sulfonate esters are separated from the sultones by chromatography on a silica gel column. Each eluent fraction is subjected to saponification and measured as active matter by MBAS determination measuring the extinction of the trichloromethane solution at 642 nra. (a) Sultones. Connor et al. [130] first reported, in 1975, a very small amount of skin sensitizer, l-unsaturated-l,3-sultone, and 2-chloroalkane-l,3-sultone in the anionic surfactant produced by the sulfation of ethoxylated fatty alcohol. These compounds can also be found in some AOS products consequently, methods of detection are essential. 

Where we have reason to suspect the involvement of a particular species as a labile intermediate in the course of a reaction, it may be possible to confirm our suspicions by introducing into the reaction mixture, with malice aforethought, a reactive species which we should expect our postulated intermediate to react with particularly readily. It may then be possible to divert the labile intermediate from the main reaction pathway—to trap it—and to isolate a stable species into which it has been unequivocally incorporated. Thus in the hydrolysis of trichloromethane with strong bases cf. p. 46), the highly electron-deficient dichlorocarbene, CClj, which has been suggested as a labile intermediate (p. 267), was trapped by introducing into the reaction mixture the electron-rich species cis but-2-ene (11), and then isolating the resultant stable cyclopropane derivative (12), whose formation can hardly be accounted for in any other way ... 

Modern carbene chemistry started, however, in a rather unusual way when Hine (1950) conducted a kinetic study of the alkaline hydrolysis of trichloromethane (chloroform). He proposed a two-step a-elimination involving CCI2 as an intermediate. The result of this mechanistic study was unusual because it opened a new field of synthetic organic chemistry, whereas, in general, such studies improve our understanding of fields already known from synthetic work. Mine s dichlorocarbene was subsequently applied to a cyclopropane synthesis by Doering and Hoffmann (1954, see later in this section). 

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