The synthesis of di-p-tolylsulfane from the reaction of 4-bromo-1-methylbenzene (BMB) with sodium sulfide was carried out using a multi-site phase-transfer catalyst (MPTC) viz., 1,4-dihexyl-1,4-diazoniabicyclo[2.2.2]octanium dibromide and ultrasonic irradiation in a liquid-liquid reaction condition. The overall reaction rate is greatly enhanced when catalyzed by multi-site phase-transfer catalyst (MPTC) combined with sonication (40 kHz, 300 W) in a batch reactor than catalyzed by MPTC without sonication. Effects on the reaction due to various operating conditions, such as agitation speed, different ultrasound frequencies, different phase-transfer catalysts, different organic solvents, the amount of MPTC, temperature, amount of sodium sulfide, effect of sodium hydroxide, volume of n-hexane and the concentration of 4-bromo-1-methylbenzene. The reaction obeys a pseudo first-order rate law and a suitable mechanism was proposed based on the experimental observation.

No abstract

The ultrasound assisted preparation of 1-(benzyloxy)-4-nitrobenzene from the reaction of 4-chloronitrobenzene (CNB) and benzyl alcohol was carried out successfully using potassium hydroxide and catalyzed by a new multi-site phase-transfer catalyst (MPTC) viz., 1,3,5-triethyl-1,3,5-trihexyl-1,3,5-triazinane-1,3,5-triium trichloride in a solid-liquid reaction condition (SL-MPTC). The advantage of using SL-MPTC is to avoid a serious hydration of potassium salt of benzyl alcohol in the reaction between 4-chloronitrobenzene (CNB) and benzyl alcohol. The reaction is greatly enhanced in the solid-liquid system, catalyzed by multi-site quaternary ammonium salt (MPTC) and ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction greatly enhanced with ultrasound irradiation than without ultrasound. The reaction mechanism is proposed and verified by examining the experimental evidence. A kinetic model is proposed in which a pseudo first-order rate law is sufficient to describe the results, such as the effects of agitation speed, ultrasound, different phase transfer catalysts and the effect of organic solvents, the amount of newly prepared MPTC, the effect of temperature, the amount of water, the concentration of 4-chloronitrobenzene (CNB) and potassium hydroxide concentrations. The apparent rate constant (kapp) were investigated in detail. Rational explanations to account for the phenomena on the results were made.

In this paper, the synthesis of ethyl 2-(naphthalen-2-yloxy)acetate from β-naphthol and ethyl 2-bromoacetate under ultrasound and catalyzed by quaternary ammonium salt in solid-liquid heterogeneous condition was described. Trace amount of water play a major role in this solid-liquid reaction. The reaction follows pseudo first order rate law. The apparent rate constant of the organic phase reaction was obtained form the experimental data. The combination of small amount of tetrabutylammonium bromide (TBAB) and ultrasound (kapp = 25.22×10 -3 min -1 ) shows several fold enhanced rate of the reaction than the conventional operation (kapp = 6.42×10 -3 min -1 for TBAB only). The rate constant increases (0.05 to 0.3 g) with increase in the concentration of catalyst (from kapp = 10.12×10 -3 min -1 to kapp = 34.46×10 -3 min -1 ). The other kinetic effects such as, effect of agitation speed, kind of frequency of ultrasound, kind of various quantity of K2CO3, quantity of water, temperature, different quaternary ammonium salts, solvents and volume of organic solvents on the conversion of ethyl 2-bromoacetate and apparent rate constant were investigated in detail and rational explanations are provided.

No abstract