Determination of Active Hydrogen Atoms

Abstract

This work was done in an endeavor to obtain satisfactory analytical data on certain alkaloids. In Zerewitinoff determinations it was found that the influence of temperature is probably often restricted to promoting solution and liberating occluded gases, that the influence of solvent is relatively unimportant, and that the activity of the hydrogen atoms of active methylene groups varies considerably with environment.

The Role of the Molecular Encapsulation Effect in Stabilizing Hydrogen‐Bond‐Rich Gel‐State Lithium Metal Batteries

“…2-(3-(2,2,2-trifluoroethyl)ureido)ethyl methacrylate (TUEM), a ureido-based precursor with abundant hydrogen-bond donors was synthesized and the corresponding gelstate polymer electrolyte (PolyTUEM-Polymer Electrolyte, abbreviated as PTUEM-PE) was prepared in situ for the first time (Figure S1). The 1 H, 19 F nuclear magnetic resonance spectroscopy (NMR) and optical photograph demonstrate that the white particles of TUEM were synthesized through nucleophilic addition of isocyanate (Figure 2a, S2-S4), and the pristine PTUEM was obtained through free radical polymerization of TUEM monomers (Figure S5, S6). It is observed that the precursors form viscous gel-state electrolytes by in situ polymerization after disassembling the cell, resulting in a homogeneous and semi-transparent membrane (Figure 2b).…”

“…[26] In addition, by calculating the relative change values of chemical shifts of À NH peaks at different FEC concentrations, the optimal FEC concentration is determined to be 5 % (Figure 2f, Table S1). Furthermore, the spatial correlations induced by the addition of FEC and the solvent-PTUEM interactions were further characterized by the 2D 1 HÀ 19 F heteronuclear overhauser effect spectroscopy ( 1 HÀ 19 F HOESY) and 1 HÀ 1 H nuclear overhauser effect spectroscopy ( 1 HÀ 1 H NOESY) experiments. [27] The 1 HÀ 19 F HOESY experiment shows a clear signal of coupling interaction ( 1 H: 5.75 ppm, 19 F: À 123.09 ppm), in which the hydrogen-bonded interaction between H atoms of PTUEM and F atoms of FEC can be observed, [28] indicating the hydrogen-bonded molecular pairs formed by the hydrogen-bond acceptors (δ À F) and hydrogen-bond donors (δ + H) between FEC and PTUEM (Figure 2g, S16).…”

“…[16] One of the overlooked challenges in some of the monomers after polymerization mentioned above lies in the presence of hydrogen-bond donors, such as amino, [14,17] hydroxyl, [15a] and carboxyl groups, [18] where the active hydrogen atoms undergo singledisplacement reactions with LMAs, leading to the decomposition of the polymer, interphase deterioration, and the release of high-risk H 2 . [19] This hinders the generation of stable solid electrolyte interphase (SEI) layers, thereby delaying the further development of in situ polymerized electrolytes in LMBs.…”