The aerobic and peroxide-induced coupling of aqueous thiols—I. Kinetic results and engineering significance

Giles, David W.; John, Anu K.; Lim, Phooi K.

doi:10.1016/0009-2509(86)85050-3

Cited by 13 publications

(4 citation statements)

References 13 publications

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“…Reactions that may be advantageously conducted in an O-W interfacial mode include reactions that are potentially useful for materials synthesis and waste treatment, such as oxidative coupling reactions (Hay, 1962;Bach, 1968; Giles et al, 1986;Chin et al, 1985) and photocatalytic degradation reactions (Hackman, 1978;Sittig, 1985). The latter are of particular interest in light of the fact that the two commonly used photocatalysts, titanium dioxide and cadmium sulfide (MacKay, 1981;Henglein, 1984), are surface-active; see Table I.…”

Section: Resultsmentioning

confidence: 99%

Segregation of metals at the oil-water interface: results and implications

Lloyd¹,

Ganesan²,

Lim³

1989

Ind. Eng. Chem. Res.

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Experimental evidence and theoretical consideration are presented to draw attention to the adsorptive power of the oil-water interface and the promising potential it provides for the development of an interfacial emulsion technique that can be useful to metal recovery and materials conversion. It is shown that dissolved and suspended metals can be segregated into a compact emulsion in between water and an immiscible oil phase and that such segregation facilitates metal recovery and interfacial catalytic reactions. On account of its property range being wider than that of solid-water and gas-water interfaces, the oil-water interface could provide a flexibility and versatility that would make the envisioned interfacial technique more useful than packed-bed and foam techniques. Other possible advantages include high capacity and high enrichment and the availability of surface variation as a convenient process parameter. Specific applications of the proposed interfacial technique are considered with reference to metal recovery and photocatalytic waste treatment.

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Section: Resultsmentioning

confidence: 99%

Segregation of metals at the oil-water interface: results and implications

Lloyd¹,

Ganesan²,

Lim³

1989

Ind. Eng. Chem. Res.

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“…A stir bar, which was controlled by the magnetic stirrer, was placed in the reactor to provide mixing and dispersion of the reaction mixture. The middle neck contained an oxygen line that led to an oxygen reservoir and a constant-pressure manometric unit that has been described elsewhere (Giles et al, 1986). The manometric unit provided a convenient and continuous monitoring of the reaction by oxygen uptake.…”

Section: Methodsmentioning

confidence: 99%

“…Before the catalyst addition, the stirring speed was increased to the maximum stable level, which was about 800 rpm. The reaction was monitored by following the oxygen uptake, which was measured using a manometric technique that has been described elsewhere (Giles et al, 1986).…”

Section: Methodsmentioning

confidence: 99%

Biphasic synthesis of poly(2,6-dimethyl-1,4-phenylene oxide) using a surface-active coupling catalyst

Dautenhahn¹,

Lim²

1992

Ind. Eng. Chem. Res.

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“…The alternate strategy of adding the catalyst last did not work in this case because the side reactions were found to occur in the absence of the catalyst. The carbonylation reaction was followed by monitoring the carbon monoxide uptake with the help of a constant-pressure manometric unit …”

Section: Methodsmentioning

confidence: 99%

Biphasic Synthesis of 2-Phenylpropionic Acid and Ester by Interfacial Carbonylation of α-Methylbenzyl Bromide

Norman

Wilhite

Pham

et al. 1998

Org. Process Res. Dev.

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An interfacial synthesis technique has been successfully extended to the carbonylation of r-methylbenzyl bromide in an organic-aqueous sodium hydroxide mixture at 35-60 °C and 1 atm using surface-active palladium-(4-dimethylaminophenyl)diphenylphosphine complex as the catalyst and dodecyl sodium sulfate as the emulsifier. Depending on the reaction conditions, 2-phenylpropionate in the form of sodium salt and an ester was obtained in 0-83% yield, along with varying amounts of side products that included r-methylbenzyl alcohol, 2,3-diphenylbutane, di(r-methylbenzyl)ether, and an asymmetric ether derived from the substrate and an alcoholic medium. When 2-methyl-1-butanol or 2-ethyl-1-hexanol was used as the organic phase, 2-phenylpropionate ester and sodium salt were obtained in 40-83% yield, with a maximum yield obtained at an optimal aqueous base concentration of about 5 M. At a lower aqueous base concentration, more of r-methylbenzyl alcohol was formed, whereas at a higher aqueous base concentration, more of 2,3-diphenylbutane and asymmetric ether were formed. When toluene was used as the organic phase, 2-phenylpropionate salt was obtained in less than 13% yield, and the major side product was r-methylbenzyl alcohol at a low aqueous base concentration and 2,3-diphenylbutane at a high aqueous base concentration. In all cases, the formation of 2,3-diphenylbutane was accompanied by a stoichiometric formation of carbonate. The latter implicates the involvement of an oxidative intermediatestentatively identified as hypobromous acidsthat could deactivate the catalyst complex through ligand degradation. Along with the carbonylation reaction, carbon monoxide also underwent a slow, base-induced hydrolysis reaction to form formic acid. With 2-ethyl-1-hexanol as the organic phase, the carbonylation of r-methylbenzyl bromide showed an apparent temperature-dependent activation energy, a first-order dependence each on the substrate, catalyst, and ligand concentrations up to the catalyst concentration of 0.0020 M and a ligand:catalyst ratio of 3:1, and a variableorder dependence on the carbon monoxide pressure that switched from first to zeroth order as the carbon monoxide pressure was increased above 450 mmHg. A reaction mechanism is proposed which yields model rate and yield expressions in accord with the experimental findings. Results of control experiments with r,r-dibromotoluene in a toluene-aqueous sodium hydroxide mixture indicate that replacement of the r-methyl group in r-methylbenzyl bromide by a second bromo group suppressed the formation of substituted benzyl alcohol and coupled product. They suggest that the broad product distribution in the carbonylation of r-methylbenzyl bromide relative to the carbonylation of benzyl chloride and r,rdibromotoluene is attributable to the electron-releasing r-methyl group making the substrate susceptible to hydrolysis and coupling reactions.

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The aerobic and peroxide-induced coupling of aqueous thiols—I. Kinetic results and engineering significance

Cited by 13 publications

References 13 publications

Segregation of metals at the oil-water interface: results and implications

Segregation of metals at the oil-water interface: results and implications

Biphasic synthesis of poly(2,6-dimethyl-1,4-phenylene oxide) using a surface-active coupling catalyst

Biphasic Synthesis of 2-Phenylpropionic Acid and Ester by Interfacial Carbonylation of α-Methylbenzyl Bromide

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