Oxygen analogy

Various sulfonium and carbosulfonium ions show remarkably enhanced reactivity upon superelectrophilic activation, similar to their oxygen analogs so do selenonium and telluronium ions. The alkylating ability of their trialkyl salts, for example, is greatly increased by protosolvation. 

Dipolar reactivity of 5-mercapto-THISs has only been demonstrated for 16 (X = S), which, like its oxygen analog, produces with dimethylfumarate, 17. and with phenylisothiocyanate, 21 (25). Compound 16 (X = S) does not react with other typical dipolarenophiles (25). 

Sulfur IS more nucleophilic than oxygen (Section 8 7) and sulfides react with alkyl halides much faster than do ethers The products of these reactions called sulfonium salts, are also more stable than the corresponding oxygen analogs... 

The tautomerism of 2-substituted 1,3-azoles (154 155) is summarized in Table 39. Whereas amino compounds occur Invariably as such, all the potential hydroxy derivatives exist in the 0x0 form, and in this series the sulfur compounds resemble their oxygen analogs. There is a close analogy between the tautomerism for all these derivatives with the corresponding 2-substltuted pyrldines. 

In contrast to the compounds 37, which undergo rapid equilibration in solution, the isomers 38a and 38b of their sulfur and oxygen analogs 38 (Scheme 20) interconvert less rapidly and can be separated (89JOC6022 91HCA1924), as can some A(A-bis(benzotriazolylmethyl)arylamines 37 (R = aryl, R = benzotriazolylmethyl) (90CJC446). 

The differenees in behavior of the eation 145 and its oxygen analog 139 are eaused by differenees in the degree of stabilization of the eharge in the C-1... 

Like their oxygen analogs, 1,3,4-thiadiazines have been reported mainly as their 6H derivatives 115 (X = S). However, Trkovnik et al. (85OPP206) showed that. 

The chemistry of pyrans and their heteroanalogs has developed significantly since 1983, when it was first reviewed by one of the authors (83AHC145). To avoid undue length to this article, only the titled hetero-pyrans are treated and the discussion of the 1-oxygen analogs will be published in the future. 

The chemistry is dependent on the particular substituents. Oxygen analogs of 31, ot-alkoxyacylates (32), do not inhibit polymerization but readily polymerize and copolyrnerize with reactivity ratios similar to methacrylate esters.191"194... 

Sulfur compounds " are better nucleophiles than their oxygen analogs (p. 439), so in most cases these reactions take place faster and more smoothly than the corresponding reactions with oxygen nucleophiles. There is evidence that some of these reactions take place by SET mechanisms. ... 

This reaction is reversible and suitable p-hydroxy alkenes can be cleaved by heat (17-34). There is evidence that the cleavage reaction occurs by a cyclic mechanism (p. 1351), and, by the principle of microscopic reversibility, the addition mechanism should be cyclic too. Note that this reaction is an oxygen analog of the ene... 

The methyl parathion released to the atmosphere can be transported back to surface water and soil by wet deposition. Methyl parathion that is released to the atmosphere can also be transformed by indirect photolysis to its oxygen analog, methyl paraoxon, by oxidation with photochemically produced oxygen radicals. However, methyl parathion is not expected to undergo significant transformation to methyl paraoxon. 

Air samples collected in the Sacramento Valley area of California near sites where methyl parathion was heavily used on rice were analyzed by Seiber et al. (1989). Methyl parathion concentrations ranged from 0.2 (minimum detectable level) to 25.67 ng/m depending on the location and time of sampling. Methyl paraoxon, the oxygen analog of methyl parathion, was also detected at a maximum of 3.07 ng/m. The highest concentrations of both compounds were found at sites near locations of heaviest use. 

Because phenol is cheaper than nitrophenol, it might cost less to condense phenol with this chloro intermediate, followed by nitration with nitric acid. This method of preparing the oxygen analog can be used as shown in Equation 40. Still another method of preparation is shown in Equation 41. 

The colorimetric method of Averell and Norris (3) for estimation of parathion is also applicable to the oxygen analog, which gives a magenta color of identical absorption peak (16). The polarographic method of Bowen and Edwards (6) is also applicable to the analysis of this ester. 

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