Thiirane structure

Fig. 7-25. Main reactions of the phenolic /8-aryl ether structures during alkali (soda) and kraft pulping (Gierer, 1970). R = H, alkyl, or aryl group. The first step involves formation of a quinone methide intermediate (2). In alkali pulping intermediate (2) undergoes proton or formaldehyde elimination and is converted to styryl aryl ether structure (3a). During kraft pulping intermediate (2) is instead attacked by the nucleophilic hydrosulfide ions with formation of a thiirane structure (4) and simultaneous cleavage of the /3-aryl ether bond. Intermediate (5) reacts further either via a 1,4-dithiane dimer or directly to compounds of styrene type (6) and to complicated polymeric products (P). During these reactions most of the organically bound sulfur is eliminated as elemental sulfur.

EtO)PS ) give 3-0- or 3-S- substituted thietanes, respectively. Thiirane structures reported as the products of several reactions have been shown to be thietanes. The acrylate adducts undergo Diels-Alder cycloadditions with butadiene, isoprene, and cyclopentadiene. ... 

Under photolytic conditions, (19) gives benzil as the main product together with tolan and trans-dibenzoylstilbene. In contrast, the 1,4-dithiin analogue (20), under both thermal and photochemical conditions, is simply converted into tetraphenylthiophene. Sulfur extrusion of this type is very common with substituted 1,4-dithiins. Thus, thermolysis of 2,6-diaryl-1,4-dithiin (23) is found to give 2,5-diarylthiophenes (24) predominantly over 3,4-diarylthiophenes (25) in various solvents. The predominant formation of (24) and (25) provides evidence that the thermal extrusion of sulfur occurs by way of a zwitterionic thiirane structure the major products are rationalized as arising from the thiirane compound, which is the more stabilized by the substituents (Scheme 1) <85H(23)1907). 

Ions having a thiiran structure have been reported to occur in the mass spectra of various sulphur-containing compounds."... 

The results of efforts to elucidate the structure of a compound derived from thioacetic acid, for which dithietan or thiiran structures once were considered and which is now established as a thioadamantane, have been... 

To summarize under favorable conditions the acidity of a-hydrogens facilitates the generation of a-sulfoxy and a-sulfonyl carbanions in thiirane and thiirene oxides and dioxides as in acyclic sulfoxides and sulfones. However, the particular structural constraints of three-membered ring systems may lead not only to different chemical consequences following the formation of the carbanions, but may also provide alternative pathways not available in the case of the acyclic counterparts for hydrogen abstraction in the reaction of bases. 

Suggest a structure for the complex. Note Thiirane is thiacyclopropane... 

Carbon-13 shift values of parent heterocycloalkanes [408] collected in Table 4.61 are essentally determined by the heteroatom electronegativity, in analogy to the behavior of open-chain ethers, acetals, thioethers, thioacetals, secondary and tertiary amines. Similarly to cyclopropanes, three-membered heterocycloalkanes (oxirane, thiirane, and azirane derivatives) display outstandingly small carbon-13 shift values due to their particular bonding state. Empirical increment systems based on eq. (4.1) permit shift predictions of alkyl- and phenyl-substituted oxiranes [409] and of methyl-substituted tetrahydropyrans, tetrahydrothiapyrans, piperidines, 1,3-dithianes, and 1,3-oxathianes [408], respectively. Methyl increments of these heterocycloalkanes are closely related to those derived for cyclohexane (Table 4.7) due to common structural features of six-membered rings. 

Alkoxide-Type Initiators. Using the guide that an appropriate initiator should have approximately the same structure and reactivity as the propagating anionic species (see Table 1), alkoxide, thioalkoxide, carboxylate, and silanolate salts would be expected to be useful initiators for the anionic polymerization of epoxides, thiiranes, lactones, and siloxanes, respectively (106—108). Thus low molecular weight poly(ethylene oxide) can be prepared... 

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