The sodium ions were introduced into the acrylic fibers by post-treating the fibers with hydrazine hydrate and aqueous sodium hydroxide to improve the flame resistance of the fibers. The molecular structure of the modified acrylic fibers was characterized by FTIR spectra. The flame resistance of the acrylic fibers was significantly increased after post-treatment and was relied mostly on the content of sodium ions. The flame-retardant mechanism of the modified fiber was studied in details. The micro calorimeter tests showed that the total heat release and the peak heat release rate were largely reduced after post-treatment. Photographs of the char residues and the results of TGA and TG-IR technique revealed that the flame retardance of the modified acrylic fiber was provided through the combination effect of the gas phase and condensed phase.
The photoredox-neutral catalyzed cyclopropanation of 1,1-disubstituted alkenes via radical addition-anionic cyclization cascade has been successfully developed. Another new protocol based on photocatalytic allylation and cyclopropanation cascade was also described between allylic halide and halomethyl radical. In addition to the successful use of bis-catecholato silicates as the alkyl radical precursors, the acyl and alkyl radicals derived from 1,4-dihydropyridines were also engaged in this radical-polar crossover process. The competing experiments displayed that the 3-exo-tet mode of cyclization preferred over 4-exo and 5-exo cyclization modes, allowing for the selective 3-exo-tet cyclization. The superior nucleofuge character of bromide over chloride and tosylate has been demonstrated in the reaction of bromomethyl radical with homoallylic (pseudo)halides. This new protocol is characterized by its redox-neutral process, broad substrate scope, mild conditions, and good functional-group compatibility.
Three novel lanthanide sulfate fluorides of formulae [C(4)H(16)N(3)](6)[Sm(4)F(2)(SO(4))(14)] 1 and LnFSO(4).H(2)O (Ln = Tb 2; Nd 3) have been synthesized solvothermally and structurally characterized by single-crystal X-ray diffraction, IR, TGA, SEM, and ICP. Single crystal X-ray diffraction reveals that compound 1 crystallizes in the triclinic crystal system, with space group P-1 and cell dimensions: a = 11.1988(9), b = 11.4073(9), c = 16.2666(13) A, alpha = 89.9010(10) degrees, beta = 82.4060(10) degrees, gamma = 67.7570(10) degrees, V = 1903.9(3) A(3), Z = 1. Both compounds 2 and 3 crystallize in the monoclinic crystal system, with the space group P2(1)/n and cell dimensions: a = 5.0014(7), b = 7.3769(11), c = 11.6508(17) A, beta = 96.692(2) degrees, V = 426.93(11) A(3), Z = 4 for 3; a = 4.9948(5), b = 7.3684(7), c = 11.6366(12) A, beta = 96.6720(10) degrees, V = 425.37(7) A(3), Z = 4 for 3. The structure of 1 consists of a novel isolated large Z-type heteropolyanion [Sm(4)F(2)(SO(4))(14)](18-) and full protonated organic amine cations. The chains are held together by hydrogen bond interactions involving the hydrogen of the amine and the framework oxygen. The compounds 2 and 3 are isostructural and their structures feature a three-dimensional network constructed from the left-handed and the right-handed helical channels which are connected by SO(4)(2-) groups using 6-membered rings and 4-membered rings.
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