Organonitrogen compounds identified in degraded wheat straw by oxidation in a sodium hypochlorite aqueous solution

摘要

Wheat straw (WS) was oxidized in a sodium hypochlorite (NaOCl) aqueous solution at 40 ℃ followed by sequential extraction of the water-soluble fraction (WSF) with petroleum ether, carbon disulfide (CDS), diethyl ether and ethyl acetate (EA). The EA-inextractable solution was acidized and filtrated. The filtration was also sequentially extracted with the same series of solvents. In total, 38 organonitrogen compounds (ONCs) were identified by GC/MS analysis from the extracts. The ONCs can be classified into amides, sulfonamides, amines, an amino acid, nitriles, an isocyanatoethane, chloro(nitro)methanes, an oxime, N-heterocyclic compounds (NHCCs, most of them are pyrrolidones) and a benzohydrazide, indicating the diversity of ONCs in WS. NHCCs, amides and nitriles are the most abundant among the ONCs, implying that these types of species might be main existing forms of nitrogen in the oxidized WS and even in WS itself to some extent. Most of the ONCs, especially amides and pyrrolidones, were enriched in the CDS-extractable fraction from the WSF because of the strong π-π interaction between C=S bond in CDS and C=O bonds in the ONCs. This investigation provides an effective approach for understanding the modes of ONC occurrences in WS.