Application of Differential Scanning Calorimetry in an Organic Chemistry Laboratory Course: Development of a Binary Phase Diagram of Cis/Trans-1, 2-Dibenzoylethylene

Abstract

In organic chemistry lab it is important to give students hands-on experiences to help them further their understanding of important chemistry topics. Binary phase diagrams incorporate many of these topics into a single graph. Differential Scanning Calorimetry (DSC) has been shown to produce data to make binary phase diagrams for alloys; however, it is more difficult to produce these diagrams using non-metal organic compounds. The purpose of this experiment was to determine if the DSC could be used to give students a challenging, yet doable experiment to prepare a binary phase diagram and determine the eutectic composition for the mixture of cis/trans-1,2-dibenzoylethylene. The conclusions from this work are: (i) The eutectic composition for cis/trans-1,2-dibenzoylethylene is at the weight percent of 30% cis and 70% trans which corresponds to an onset melting temperature of 93.5°C; (ii) as the cis increased from a weight percent of 30% the melt temperature also increased; (iii) as the trans increased from a weight percent of 70% the melt temperature also increased; (iii) the DSC produced sufficient data necessary to develop a binary phase diagram of peak melt temperatures vs the weight percent of the cis isomer; (iv) the DSC could be incorporated into an organic chemistry lab to enhance student’s knowledge of important topics while giving them an experience working with advanced laboratory thermal instruments.