Structure and activity relationship studies of N-heterocyclic olefin and thiourea/urea catalytic systems: application in ring-opening polymerization of lactones was written by Zhou, Li;Wang, Zhenyu;Xu, Guangqiang;Lv, Chengdong;Wang, Qinggang. And the article was included in Polymer Chemistry in 2021.HPLC of Formula: 2387-23-7 This article mentions the following:
A highly efficient and controllable ring-opening polymerization of lactones (δ-valerolactone, ε-caprolactone and rac-lactide) has been achieved by using N-heterocyclic olefin (NHO) and thiourea/urea (TU/U) catalytic systems. This catalytic system showed high ring-opening activity and stereoselectivity, delivering biodegradable polyesters with high chain-end fidelity, controlled mol. weights and narrow molar mass dispersities. A detailed investigation of the structure-activity relationship was performed by exploring five NHOs and fourteen TUs/Us. For a fixed NHO, when the acidity of TUs/Us decreases, the polymerization mechanism changes from the (thio)urea anion to the neutral cooperative activation mode, and the catalytic activity first increases and decreases, displaying a highly effective interval. For a given TU or U, as the basicity of NHOs increases, the catalytic performance improves correspondingly. Besides, highly isoselective ROP of rac-LA (Pm = 0.93) at -78° has been also achieved, highlighting the versatility of the NHO/TU(U) system. These findings enrich the type of TU/U and base organocatalyst. In the experiment, the researchers used many compounds, for example, 1,3-Dicyclohexylurea (cas: 2387-23-7HPLC of Formula: 2387-23-7).
1,3-Dicyclohexylurea (cas: 2387-23-7) belongs to amides. In primary and secondary amides, the presence of N–H dipoles allows amides to function as H-bond donors as well. Thus amides can participate in hydrogen bonding with water and other protic solvents; the oxygen atom can accept hydrogen bonds from water and the N–H hydrogen atoms can donate H-bonds. Amides can be recrystallised from large quantities of water, ethanol, ethanol/ether, aqueous ethanol, chloroform/toluene, chloroform or acetic acid. The likely impurities are the parent acids or the alkyl esters from which they have been made. The former can be removed by thorough washing with aqueous ammonia followed by recrystallisation, whereas elimination of the latter is by trituration or recrystallisation from an organic solvent.HPLC of Formula: 2387-23-7
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics