Chlorosuccinic acid

In 1896, the German chemist Paul Walden made a remarkable discovery. He found that the pure enantiomeric (+)- and (-)-malic acids could be intercon-veited through a series of simple substitution reactions. When Walden treated (-)-malic acid with PCl5, he isolated (4-)-chlorosuccinic acid. This, on treatment with wet Ag20, gave (+)-malic acid. Similarly, reaction of (+)-malic acid with... 

PC15 gave (-)-chlorosuccinic acid, which was converted into (-)-nialic acid when treated with wet Ag20. The full cycle of reactions reported by Walden is shown in Figure 11.1. 

At this point, it is desirable for us to see just how it was originally proved that a given substitution reaction proceeds with inversion of configuration, even before the mechanism was known. Walden presented a number of examples in which inversion must have taken place. For example, (+)-malic acid could be converted to ( + )-chlorosuccinic acid by thionyl chloride and to (— )-chlorosuccinic acid by phosphorus pentachloride ... 

The student may wonder just what the mechanism is in cases where retention of configuration is involved since it certainly is not simple Sn2. As we shall see later, the reaction between malic acid and thionyl chloride is an SNi process (p. 420), while a neighhoring-group mechanism (p. 404) is involved in the treatment of chlorosuccinic acid with silver oxide. 

But the fact that a change of configuration occur on the path II —> III —> IV or III —> IV —> I is clear since by a two stage process an optically active compound (+)-. chlorosuccinic acid in COOH COOH COOH... 

Chlorosalicylic acid, see MCPA Chlorosuccinate, see 2,4,5-T Chlorosuccinic acid, see 2,4,5-T... 

In the conversion of malic acid to chlorosuccinic acid, an inversion of configuration at C-2 was presumed. This point is immaterial, however, since chirality is finally lost at this position. The (2/ )-[2-2H]succinic acid, 89, had a plain negative ORD curve. The configurational assignment rests on the correctness of that for malic acid. 

The addition of ammonia to these substrates occurs via A-attack at the S7-face of C-3, with protonation occurring from the 7 e-face of C-2, yielding the functionalized aspartic acid having the (27 ,3S)-configuration40 b. The absolute configuration of the chloroaspartic acid was determined by reduction (H2/Pd - C) to L-aspartic acid ([a]D + 21.5), and by two-step conversion to (Z)-2-chloro-2-butenedioic acid (diazotization in the presence of the bromide ion with retention of configuration, followed by elimination of hydrobromic acid from the intermediate 2-bromo-3-chlorosuccinic acid). 

If the products of a reaction are capable of existing in more than one stereoisomeric form, the form that is obtained may give information about the mechanism. For example, (+)-malic acid was discovered by Walden to give (—)-chlorosuccinic acid when treated with PCI5 and the (+) enantiomer when treated with SOCI2,... 

Kryger, L., Rasmussen, S. E., and Danielsen, J. Walden inversion. I. The crystal structure and absolute configuration of (-)-chlorosuccinic acid. Acta Chem. Scand. 26, 2339-2348 (1972). 

In 1899, Centnerszwer [16] observed that (+)-chlorosuccinic acid and (—)-bromosuccinic acid form what was then termed a molecular compound . In fact, the same behavior had been noted by Pasteur in one of his earliest papers on optical activity [17]. In general, one would not expect cocrystallization of two different compounds. A and A, unless there is a strong, specific interaction (e.g. hydrogen bond formation) between them [18]. However, if A and A are very similar in shape (isosteric), then special situations can arise. The like-handed compounds, e.g. (R)-A and (i )-A, could... 

Addition of beryllium sulphate does not effect rotatory power of dextrose, or chlorosuccinic acid. 

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