Preparing 4-Ethoxyphenylurea Using Microwave Irradiation: Introducing Students to the Importance of Artificial Sweeteners and Microwave-Assisted Organic Synthesis (MAOS)

Abstract

In today's world of instant coffee, instant meals, and instant messaging, undergraduate students prefer not to have to wait 30−60 min for an organic reaction to take place. Heating with microwaves is rapidly becoming more commonplace due to dramatically reduced reaction times and higher product yields. Students appreciate the short reaction times and like working with advanced technology by means of the commercial microwave reactors available today. Furthermore, undergraduate organic students like being able to relate an experiment to something that they see every day. For these reasons, the synthesis of pharmaceuticals, extracting caffeine from tea, and isolating trans-cinnamaldehyde from cinnamon sticks are popular experiments. One such experiment is the synthesis of the artificial sweetener dulcin (4ethoxyphenylurea), which can be prepared from the reaction of p-phenetidine and urea. Artificial sweetening agents are extremely important to the food industry because of the national concern with diet and weight control. The synthesis of this particular sweetener typically takes at least 30 min to reach completion. However, using microwave irradiation, the reaction reached completion in 5 min using a temperature of 125 °C. This procedure was implemented into the second semester undergraduate organic chemistry laboratory curriculum where students successfully prepared dulcin with reported yields ranging from 10% to 86% and an average yield of 39% after recrystallization.

Microwave-Aided Reactions of Aniline Derivatives with Formic Acid: Inquiry-Based Learning Experiments

“…Microwave irradiation appears in various forms in a wide range of human activities. The application of microwaves has also found its place in chemistry, as well as in chemistry education (e.g., Diels-Alder cyclisation, Wittig reaction, Williamson ether synthesis) [32][33][34][35][36][37][38][39][40][41][42]. Microwaves can also be found in other chemical fields, such as pre-treatment of samples in analytical chemistry replacing classical mineralisation [43].…”

Updating the Benzoin Condensation of Benzaldehyde Using Microwave-Assisted Organic Synthesis and N-Heterocyclic Carbene Catalysis

“…The 60 °C method also uses a thermostated water or oil bath, which is a significant expenditure of energy when every student requires space in the bath. We proposed that the energy expenditure and reaction times could be dramatically lessened by using microwave-assisted organic synthesis (MAOS) …”

Green Fischer Indole Synthesis Using a Steroidal Ketone in a Conductively Heated Sealed-Vessel Reactor for the Advanced Undergraduate Laboratory

“…1 In terms of the teaching laboratory, the shorter reaction times afforded by microwave-assisted organic synthesis (MAOS) prevent extended waiting periods that are not popular with students, as they can become disengaged. 2 MAOS also allows the study of reactions that would typically not be considered because they are too long to fit into the standard 4 h laboratory period. 2 Finally, state-of-the-art technology in the laboratory is an excellent recruitment tool that can have positive effects on students' decision to pursue research later on.…”

“…2 MAOS also allows the study of reactions that would typically not be considered because they are too long to fit into the standard 4 h laboratory period. 2 Finally, state-of-the-art technology in the laboratory is an excellent recruitment tool that can have positive effects on students' decision to pursue research later on. 3 Recently, a conductively heated sealed-vessel reactor that effectively works as a mock microwave reactor was introduced.…”

“…Apart from using less energy, the practice often results in higher yields and fewer side products . In terms of the teaching laboratory, the shorter reaction times afforded by microwave-assisted organic synthesis (MAOS) prevent extended waiting periods that are not popular with students, as they can become disengaged . MAOS also allows the study of reactions that would typically not be considered because they are too long to fit into the standard 4 h laboratory period .…”