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Such reactions give alkenes in the case of vicinal alkyl dihalides: [2] R 2 C(X)C(X)R 2 + M → R 2 C=CR 2 + MX 2. Most desirable from the perspective of remediation are dehalogenations by hydrogenolysis, i.e. the replacement of a C−X bond by a C−H bond. Such reactions are amenable to catalysis: R−X + H 2 → R−H + HX
In it, Zaytsev proposed a purely empirical rule for predicting the favored regiochemistry in the dehydrohalogenation of alkyl iodides, though it turns out that the rule is applicable to a variety of other elimination reactions as well. While Zaytsev's paper was well referenced throughout the 20th century, it was not until the 1960s that ...
Dehydrohalogenation to give an alkene In chemistry , dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate . The reaction is usually associated with the synthesis of alkenes , but it has wider applications.
Using a carboxylate-to-iodine ratio of 1:1 leads to an alkyl iodide product, in line with Borodin's findings and the modern understanding of the Hunsdiecker reaction. However, a 2:1 ratio favours the formation of an ester product that arises from decarboxylation of one carboxylate and coupling the resulting alkyl chain with the other. [9] [10]
The iodide anion is a good nucleophile and will displace chloride, tosylate, bromide and other leaving groups, as in the Finkelstein reaction. Alcohols can be converted to the corresponding iodides using phosphorus triiodide. Illustrative is the conversion of methanol to iodomethane: [15] PI 3 + 3 CH 3 OH → 3 CH 3 I + "H 3 PO 3 "
The classic Finkelstein reaction entails the conversion of an alkyl chloride or an alkyl bromide to an alkyl iodide by treatment with a solution of sodium iodide in acetone. Sodium iodide is soluble in acetone while sodium chloride and sodium bromide are not; [ 3 ] therefore, the reaction is driven toward products by mass action due to the ...
However, if an unreactive alkylating agent is used (e.g. an alkyl chloride) then the rate of reaction can be greatly improved by the addition of a catalytic quantity of a soluble iodide salt (which undergoes halide exchange with the chloride to yield a much more reactive iodide, a variant of the Finkelstein reaction).
The scope of the Corey-House synthesis is exceptionally broad, and a range of lithium diorganylcuprates (R 2 CuLi, R = 1°, 2°, or 3° alkyl, aryl, or alkenyl) and organyl (pseudo)halides (RX, R = methyl, benzylic, allylic, 1°, or cyclic 2° alkyl, aryl, or alkenyl and X = Br, I, OTs, or OTf; X = Cl is marginal) will undergo coupling as the nucleophilic and electrophilic coupling partners ...