Thiophenoxide ion

The trichloro derivative reacts rapidly at room temperature with sulfide, hydrosulfide, alkylmercaptide, or thiophenoxide ions in the solid phase, in water, or in organic solvents. 

As expected, the addition of arenediazonium ions to thiophenols does not involve the thiophenol molecule, but rather the thiophenoxide ion (Price and Tsunawaki, 1963). Dediazoniation with the formation of a diarylsulfide (6.16) is competitive with the formation of the diazo thioether 6.15 (Scheme 6-9 van Zwet et al., 1970). Whereas the early investigators detected only one isomer, (Z)- and (ii)-forms were... 

Since both reactions form phenol, Bunnett coined the phrase ad eundem competition, from the Latin, meaning (leading) to the same (product, singular). As such, a product ratio cannot allow the determination of h2oAoh However, if one adds thiophenoxide ion, PhS-, as a third competing reagent for benzyne, then diphenyl sulfide is formed,... 

The drastic change in the reactivity of oxygen nucleophiles is also found in several other examples. Thiolate anions are classified as stronger nucleophiles than their oxyanionic counterparts (DeTar and Coates, 1974 Williams and Donahue, 1978). It was found, however, that towards PNPA in dimethyl-formamide the nucleophilic reactivity of thiophenoxide ion exceeds that of phenoxide ion when [H20] = ca. 1000 mM but the relative reactivity was sharply reversed below [H20] = 300 mM (Shinkai et al., 1979a). Therefore, phenoxide ion can be a much stronger nucleophile than thiophenoxide ion in very dry aprotic solvents. 

C. P. Andrieux, P. Hapiot, J. Pinson, J.-M. Saveant. Determination of Formal Potentials of Chemically Unstable Redox Couples by Second-Harmonic Alternating Current Voltammetry and Cyclic Voltammetry. Application to the Oxidation of Thiophenoxide Ions. J.Am. Chem. Soc. 1993,115, 7783-7788. 

Westaway and co-workers (Westaway and Lai, 1988 Lai and Westaway, 1989 Fang and Westaway, 1991) found that the secondary a-deuterium KIE in the Sn2 reaction between butyl chloride and thiophenoxide ion (reaction (26)) was concentration dependent. 

Table 26 The secondary a-deuterium KIEs for the SN2 reactions between butyl chloride and thiophenoxide ion when the nucleophile is a contact ion-pair, a solvent-separated ion-pair complex and a free ion at 200C.0...

Table 27 The secondary a-deuterium and primary nitrogen KIEs for the free ion and ion-pair SN2 reactions between benzyldimethylphenylammonium nitrate and p-substituted thiophenoxide ions in methanol at 2Q°C.a...

Fig. 14 The relative transition state structures for the SN2 reactions between benzyldimethylphenylammonium ion and free p-substituted thiophenoxide ions in methanol at 20°C. Reproduced, with permission, from Westaway (1996).

The nucleophile in the S.v2 reactions between benzyldimethylphenylammonium nitrate and sodium para-substituted thiophenoxides in methanol at 20 °C (equation 42) can exist as a free thiophenoxide ion or as a solvent-separated ion-pair complex (equation 43)62,63. The secondary alpha deuterium and primary leaving group nitrogen kinetic isotope effects for these Sjv2 reactions were determined to learn how a substituent on the nucleophile affects the structure of the S.v2 transition state for the free ion and ion-pair reactions64. 

Attention may now be directed to the reactions of aromatic thiols with epoxides. Mu tz,IH for example, haa investigated the course of addition of thiophenol to propylene oxide, both in alkaline and in acidic solutions. Significantly lower yields obtained in acid tended to confirm the premise that thiophenoxide ion rather than undissociated thiophenol is the attacking nucleophile. Likewise predictable was the isolation of two isomeric phenylthioprcpanois under add conditions, hut of only one in base (Eq. 663). 

For example, the rate of displacement of bromide by thiophenoxide ion in l-bromo-2-chloroethane is slowed down by a factor of 5 compared to substitution in the structurally similar 1-bromopropane (Equations 4.13 and 4.14).33 But the... 

Another reason for the apparent inconsistencies in experimental data is that, depending on the nature and position of the substituent, steric and conjugative effects often outweigh polar influences. In order to study pure polar effects, Holtz and Stock have carried out rate studies of displacements by thiophenoxide ion on 4-Z-bicyclo-[2.2.2]-octylmethyl toluenesulfonate (Equation 4.17).37... 

Table 4.3 Relative Rates of 4-Z-Bicyclo[2.2.2]ocTYLMETHYL Toluenesulfonate with Thiophenoxide Ion...

Thiophenoxide ion reacts with PhC=CC02Me in DMF containing 0.5% MeOH to give a mixture of ( )- and (Z)-products PhC(SPh)=CHC02Me. The rate constant depends on the MeOH concentration, indicating a third-order reaction. The plot of log 3 vs Hammett a constants varies from 0.42 to 0.77, depending on the temperature. The activation parameters and p values are consistent with a concerted mechanism.79... 

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