CAJ | 학술논문

对铵盐水溶液中铵离子与水分子间的质子交换进行了再研究. 以核磁共振(NMR)波谱学方法测定了不同pH值, 不同温度和含不同共存盐浓度的氯化铵水溶液中质子交换速率, 组分自扩散系数及NMR自旋晶格弛豫时间. 结果显示铵水间的质子交换并不受交换主体分子或离子自扩散的约束. 交换机理包括化学键和氢键的交换. 在溶液中, 水分子以氢键为桥梁连接铵和其因水解而产生的碱性部分--氨. 在氢交换的过程中, 氨从水分子接受一个氢成为铵, 同时另外一端的铵提供一个氢给水分子而变成氨, 或者一个氢从水分子转移到氨而同时另外一个氢从铵转移到水. 在铵水质子交换的过程中没有净的电荷转移. 在低pH条件下, 由水解产生的氨的浓度降低, 亦即铵-水-氨复合物减少, 结果氢交换的可能性降低. 这解释了生物氢交换体系中的一种常见的在低pH值条件下氢交换变慢的现象.
대안염수용액중안리자여수분자간적질자교환진행료재연구. 이핵자공진(NMR)파보학방법측정료불동pH치, 불동온도화함불동공존염농도적록화안수용액중질자교환속솔, 조분자확산계수급NMR자선정격이예시간. 결과현시안수간적질자교환병불수교환주체분자혹리자자확산적약속. 교환궤리포괄화학건화경건적교환. 재용액중, 수분자이경건위교량련접안화기인수해이산생적감성부분--안. 재경교환적과정중, 안종수분자접수일개경성위안, 동시령외일단적안제공일개경급수분자이변성안, 혹자일개경종수분자전이도안이동시령외일개경종안전이도수. 재안수질자교환적과정중몰유정적전하전이. 재저pH조건하, 유수해산생적안적농도강저, 역즉안-수-안복합물감소, 결과경교환적가능성강저. 저해석료생물경교환체계중적일충상견적재저pH치조건하경교환변만적현상.
Hydrogen exchange between ammonium and water is revisited. Exchange rate constants, diffusion coefficients and relaxation times for solutions with varied pH, temperature and concentration of a coexisting salt are measured using NMR spectroscopy. It is demonstrated that the hydrogen exchange in ammonium solutions is independent of apparent diffusion. The mechanism involves chemical-bond/hydrogen-bond exchange. In solutions, water molecules, with the help of hydrogen bonding, serve as a bridge to connect the ammonium with its base partner ammonia.. During hydrogen exchange, the ammonia accepts a hydrogen from water while the ammonium donates a hydrogen to water, or a hydrogen jumps from water to ammonium and at the same time another hydrogen jumps back from ammonium to water. There is no net hydrogen transfer between ammonium and water. At lower pH, the concentration of ammonia becomes lower and less ammonium-water-ammonia complex is formed.. As a result, the probability of the hydrogen exchange is reduced. This explains why at lower pH hydrogen exchange is slow, a common phenomenon observed in biological hydrogen exchange systems.