Quality of Microscale Laboratory Synthesis of Organic Crystalline Solids by DSC and Capillary Melting

摘要

Microscale laboratory synthesis of organic crystalline compounds is an integralrnpart of undergraduate organic chemistry and industrial research and development.rnCollege students numbering from 10 to 20 per laboratory prepare various organicrncompounds and verify their products with capillary melting temperatures.rnImplementation of Differential Scanning Calorimetry is in order to better qualify therncrystalline products. The following chemicals were prepared in an undergraduaternlaboratory: 9-bromoanthracene, Diels-Alder reaction product, 9-flurone, the derivative ofrn9-fluorone with 2,4-dinitrophenylhydrizone and SalenH2. The student capillary meltrntemperatures were compared to the DSC, melting temperature, peak temperature and heatrnof fusion. The DSC protocols called for measurement of the melt and in some casesrnquench cooling and examining the sample a second time. The DSC study included tworndifferent DSC apparatus and operators. The observed DSC properties were reproduciblernand repeatable. The DSC can reveal varying qualities of the reaction products. A highrnquality Diels Alder product melted at 300-305C [DSC]. A less pure Diels Alder samplernmelted at a significantly lower temperature and one of the reactants, a melting endothermrn, was noted.