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EN
Nucleophiles add to electron-deficient arenes, also those containing halogens, initially in positions occupied by hydrogen to form óH adducts. This addition is faster than addition in similarly activated positions occupied by halogens. Formation of the óH adducts is a reversible process, thus they dissociate and slower addition in positions occupied by halogens results in formation of óH adducts followed by fast departure of X– to form products of nucleophilic substitution of halogen, SNAr. In the review it is shown that there are a few ways for fast further conversion of initially formed óH adducts into products of nucleopilic substitution of hydrogen such as oxidative substitution, vicarious substitution, etc. Since formation of óH adducts is faster than óH adducts and the former undergo fast transformations into products of nucleophilic substitution of hydrogen we should accept than this is the major, primary reaction whereas conventional nucleophilic substitution of halogens, SNAr reaction “ipso” substitution is just a secondary process. In modern textbooks only SNAr reactions are discussed whereas nucleophilic substitution of hydrogen is not mentioned, thus it is necessary to introduce proper corrections in textbooks and teaching of this chapter of chemistry of arenes.
EN
Relative electrophilic activities of substituted nitroarenes in the vicarious nucleophilic substitution (VNS) reaction with carbanion of chloromethyl p-chlorophenyl and bromo - methyl phenyl sulfones, 1 and 2, were determined via competitive experiments. The results are in good agreement with relative activities determined earlier in the competitive experiments with carbanion of chloromethyl phenyl sulfone 3 confirming reliability of these data. On the other hand, analogous competitive experiments with tertiary carbanions of chloroform and 1-chloroethyl phenyl sulfone gave results much affected by steric effects thus the VNS reaction with these carbanions can not be used for evaluation of electrophilic activities of nitroarenes.
EN
Recent results of oxidative nucleophilic substitution of hydrogen in nitroarenes with carbon, nitrogen, oxygen etc. nucleophiles and discussion of oxidants used in these reactions are presented.
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