| http://www.w3.org/ns/prov#value | - All the chemicals, such as hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), thionyl chloride (SOCl2), tetrahydrofuran (C4H8O), ethylenediamine [C2H4(NH2)2] and formic acid (HCOOH) were of analytical grade with >99.9% purity were obtained from Sigma-Aldrich (Shanghai, China).
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