Green Synthesis and Crystal Structure of Regioselectively Substituting 6-O-tritylcellulose Derivatives

The tritylation of cellulose was respectively performed in different ionic liquids (ILs) of 1-butyl-3-methylimidazolium chloride (BMIMCI), 1-allyI-3-hexylimidazolium chloride (AHIMCI) and 1-ethyl-3-methylimidazolium phosphorous methyl ester (EMIMMeOPO2H) using catalysts as base. It was found that the catalyst with moderate alkalinity exhibited perfect capability to facilitate the tritylation of cellulose in ILs. The observations between the different ILs demonstrated the large influence of the ILs structure on the trityl group attacking the C6-OH of cellulose. The trityl group attacks both the C6, C2-OH of cellulose backbone, but cannot be removed completely at C6 after detritylation. It was interestingly reported that the establishment of new crystalline structures (pi-pi stacking) was observed at the 6-O-tritylcellulose derivatives with higher Degree of Substitution (DS) value. The introduction of trityl groups onto the cellulose backbone contributes to the improvement of the thermal properties of the 6-O-tritylcellulose derivatives due to more molecular regularity from the sufficient benzene structures.