Differential Scanning Calorimetry and Thermogravimetric Analysis
In an effort to evaluate the reactivity of the 1,2-diethynylbenzenes upon heating, the
thermal properties of 1 were investigated using differential scanning calorimetry (DSC).
The trace in Fig.S1 shows a sharp endothermal peak at 44 °C associated with the melting
point of the sample, and a broad exothermal feature centered around 120 °C characteristic
for a thermally induced cyclization process (29). Repeated cycles of heating and cooling
indicate that the latter peak is coupled to an irreversible transformation of 1.
4
Thermogravimetric analysis (TGA) of the same sample indicates only a < 1% mass loss
in the temperature range between 100 and 150 °C. We thus conclude that the exothermal
peak is not associated with the thermal decomposition of 1.