Replacement s. a. Substitution Trans

Removal s. Elimination, Protective groups, removal Replacement (s. a. Substitution, Trans...)... 

Kumakov s test (1893) is generally applicable to cis- and trans-ammine dihalides. Addition of thiourea (tu, (H2N)2CS) to the cA-complex leads to successive replacement of all the ligands (Figure 3.29) here the lability of the Pt—Cl bond (see section 3.8.9) causes substitution of a chloride. 

In the first step of scheme (7.31 -7.32), L replaces Y from the cis isomer to form an ionic intermediate [PtLjXJ X . In the second step, X replaces L to produce the trans-xsomex (or revert to the c/s-form). The two steps are required to get around the fact that substitution at Pt(ll) is stereospecific (Sec. 4.6). It appears to operate in a variety of conditions but may be more complicated than indicated in Scheme (7.31) and (7.32). ... 

In 1893 a third important regularity was observed by Nikolai Semenovich Kumakov (1860—1941).107 While investigating the substitution of ligands by thiourea and thioacetamide, Kumakov found that replacement occurs with all the ligands of the cis compound but only with the acid radicals of the trans compound (Scheme 2). Since the two isomers yield different products, this reaction, known as Kumakov s reaction or Kumakov s test, may be used to differentiate cis from trans isomers of dipositive platinum or palladium. Kumakov s classic reaction played a crucial role in Werner s proof of the square planar configuration of Pt11 and in Chemyaev s formulation of the trans effect. 

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