Figure 3A represent the evolution of the conversion of EDC into 1a (red plot) as a function of time. The slope of the corresponding second-order plot (Figure , red plot) indicates that the second-order rate constant k1,EDC of the ring-opening reaction of EDC is equal to 0.75 L mol -1 s -1 . To our knowledge, very few kinetic rate constants have been measured at 25 °C for the aminolysis of 5-membered cyclic carbonate, because these ring-opening additions are usually very slow close to room temperature. Only 5-membered CC activated by very strong electron withdrawing substituent can display a significant aminolysis rate at room temperature. Our group measured a kinetics rate constant, kester, of about 0.42×10 -4 L mol -1 s -1 at 25 °C for the ring opening addition of HA onto a strongly activated CC with an ester as 𝛽𝛽-substituent (DMSO, 1 mol L -1 ). The kinetics rate constant of the first ring opening of EDC is much larger, k1,EDC ~ 10 4 ×kester, illustrating once again the strong mutual activation of the vicinal CC units. In order to study the subsequent ring-opening aminolysis of the in-situ generated monocarbonate 1a, an additional equivalent of HA was added to the reaction mixture. Again, the reaction progress was monitored by H NMR spectroscopy at 25 °C by monitoring the progress of the integral of signal y. The green plot of Figure indicates that the conversion of CC is much slower this time. The second-order rate constant k2 was calculated to be 0.064 L mol -1 s - 1 , i.e., k2,EDC ~ k1,EDC/10. The reaction was brought to completion by increasing the temperature to 60 °C for a total of 4 hours. The NMR analysis of the crude indicate that both the 2a and 2a' compounds are formed (Figure and Figure to S9). Indeed, 16% of the overall hydroxyl groups in the crude are (OH)I, indicating that 2a' was formed. The ratio of the two regioisomers can be calculated to be 2a:2a' = 68:32. Thus, the second ring opening addition is not regiospecific, however there is a significant orientation of the regiocontrol in favor of (OH)II formation. In their work dedicated to the polymerization of EDC with various diamines, Schmidt et al. measured (OH)I : (OH)II ~ 35 : 65 for PHUs synthetized in DMSO at 100°C, i.e. a regioselectivity oriented towards the formation of (OH)II as well. The ratio measured in our study, for model molecules and at 25 °C -60 °C, indicates a higher orientation of the regioselectivity towards the formation of (OH)II. This might suggest that the regioselectivity is dependent on the nature of the substrates and the reaction conditions. However, it is worth noting that the assignments of the NMR signals of erythritol PHUs are not consistent with ours and were not confirmed by COSY, HSQC and HMBC NMR analysis.