Regioselective nitration of phenol under continuous microwave irradiation

ABSTRACT

This study deals with the nitration of phenol in a multimode MW reaction system operating under continuous microwave (MW) irradiation. Reactions were carried out with two nitric acid (HNO₃)/phenol molar ratios: 1.25 and 1.1, under the following conditions: applied (nominal) MW power, P_nom = 600 W, adsorbed power P = 16.0 kW dm⁻³, reaction temperature, T_R = 68–90 °C, reaction time, t = 5–9 min, heating rate 0.1–0.25 °C s⁻¹. At the end of the synthesis, para/ortho (p/o) isomer distribution of nitrophenol product was determined by high-pressure liquid chromatography (HPLC). Furthermore, conventional (CH) experiments were conducted also under the same conditions. Then, MW and CH methods were compared in terms of product yield and isomer distribution. According to results, yield and para-selectivity of MW-assisted synthesis were higher than the CH counterpart although the reaction temperature of the MW method was lower than that of the CH method.

KEYWORDS:

• Microwave effect
• simultaneous cooling
• ecofriendly
• green nitration
• nitrophenol
• selective nitration
• para-selectivity

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Gebze Technical University (GTU) research fund.

Notes on contributors

Başak Temur Ergan

Başak Temur Ergan received PhD degree in chemical engineering from Gebze Technical University, Turkey, in 2013. She is currently in the department of chemical engineering, Gebze Technical University. Her main research interests are process and reactor design, microwave reactors, chemical kinetics, modelling and analysis of microwave-assisted processes, polymer and biopolymer processes, renewable energy, application of microwave heating.

Mahmut Bayramoğlu

Mahmut Bayramoğlu received PhD degree in chemical engineering from Istanbul University, Turkey in 1983. Currently he is a professor of the Gebze Technical University. His main research interests are process modelling, process analysis and optimization, renewable energy resources, direct alcohol fuel cell, sonochemistry applications, microwave chemistry applications, wastewater treatment.

Elif Şahin

Elif Şahin received master degree in chemical engineering from Gebze Technical University, Turkey, in 2009. She is currently a teacher of Private Enka Schools in Gebze.