Nilsson Emelie J, Alfredsson Viveka, Bowron Daniel T, Edler Karen J
Physical Chemistry, KILU, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
ISIS, Science and Technology Facilities Council Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, UK.
Phys Chem Chem Phys. 2016 Apr 28;18(16):11193-201. doi: 10.1039/c6cp01389a.
We have investigated the properties in water of two tetraalkylammonium bromides (tetramethylammonium, TMA(+), and tetrapropylammonium, TPA(+)), at 0.4 M, using neutron scattering coupled with empirical potential structure refinement to arrive at an atomistic description. Having both a polar and an apolar moiety, it is of interest to determine the strength of each moiety as a function of the alkyl chain length. TMA(+) and TPA(+), having different impact as structure directors in zeolite synthesis, were chosen for this study. Water arranges tetrahedrally around TMA(+) and in an almost featureless manner around TPA(+). TMA(+) and TPA(+) show an apolar hydration with TPA(+) being slightly more apolar. TPA(+) has a tendency to form small clusters of 2-4 molecules and to fold into a compact configuration. Both molecules correlate similarly with the bromide ion but do not dissociate completely at this concentration.
我们使用中子散射结合经验势结构精修，在0.4M浓度下研究了两种溴化四烷基铵（四甲基铵，TMA(+)，和四丙基铵，TPA(+)）在水中的性质，以获得原子尺度的描述。由于同时具有极性和非极性部分，确定每个部分的强度如何随烷基链长度变化很有意义。在沸石合成中作为结构导向剂具有不同影响的TMA(+)和TPA(+)被选用于本研究。水在TMA(+)周围呈四面体排列，而在TPA(+)周围几乎呈无特征的排列方式。TMA(+)和TPA(+)表现出非极性水合作用，其中TPA(+)的非极性稍强。TPA(+)有形成2 - 4个分子的小聚集体并折叠成紧密构型的倾向。两种分子与溴离子的相关性相似，但在此浓度下不会完全解离。
