Propionic anhydride

Pieces of Japanese cypress (Chamaecyparis obtuse) (Yamani, Co., Ltd., Nagano, Japan) with dimensions of 5.0 mm (longitudinal direction, L) × 20 mm (radial direction, R) × 20 mm (tangential direction, T) were used as wood specimens. The specimens were cut from a larger piece with a transverse section of 20 mm (R) × 20 mm (T). The initial mass of these specimens was ~0.7 g. Methanol, propionic anhydride (PA), trifluoroacetic anhydride (TFAA), propionic acid, 4-dimethylaminopyridine (DMAP), N-methyl pyroridone, sodium hydrogen sulfate, and sulfuric acid (SA) were purchased from FUJIFILM Wako Pure Chemical Corp. (Osaka, Japan) and utilized as obtained.

Hydroxypropyl cellulose (HPC) was purchased from Tokyo Chemical Industry Co., Ltd. (TCI) and the molecular parameters are as follows: number- and weight-average molecular weights, 9.9 × 10⁴ and 1.5 × 10⁴ respectively; degree of substitution, DS = 1.4 and MS = 3.9,^{28 (link)} where DS and MS denote an average number of substituted hydroxyl group and that of introduced hydroxypropyl group, respectively. Methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), ethyl methacrylate (EMA), isopropyl methacrylate (iPMA), and 4-acryloylmorpholine (ACMO) were obtained from TCI and used after passing through a column packed with activated alumina (Wako Pure Chemical Industries, Ltd. (Wako)). Dehydrated pyridine (Wako), propionic anhydride (TCI), 4-dimethylaminopyridine (DMAP) (Wako), 2-hydroxy-2-methylpropiophenone (HMPPh) (Sigma Aldrich Co. LCC.) were used without further purification.