EASILY POLARIZABLE HYDROGEN-BONDS IN AQUEOUS-SOLUTIONS OF ACIDS - PERCHLORIC-ACID AND TRIFLUOROMETHANE SULFONIC-ACID
EASILY POLARIZABLE HYDROGEN-BONDS IN AQUEOUS-SOLUTIONS OF ACIDS - PERCHLORIC-ACID AND TRIFLUOROMETHANE SULFONIC-ACID
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DOI：
10.1039/f29787402256
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发表时间：
1978-01-01
期刊：
影响因子：
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通讯作者：
ZUNDEL, G
中科院分区：
文献类型：
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作者：
LEUCHS, M;ZUNDEL, G
用红外光谱研究了高氯酸和三氟甲烷磺酸水溶液的浓度变化规律。光谱学。解离程度是由酸分子特征带的吸光度确定的。易极化的氢键由IR表示。康涅瓦。在高浓度溶液(水：酸比n<；1)中，形成了易极化的酸水氢键AH[图略]OH2⇌A-[图略]H+OH2。质子限制结构的重量表明，这些氢键的能面是不对称的双极小值，水分子处的深井。水分子的振动受质子的影响很大，或多或少具有H3O+的性质。随着n的增加，在n=1.8(HCIO4)或n=1.6(CF3SO3H)时发生完全解离。首先，质子限制结构II的重量增加，然后形成H5O+2，具有H3O+性质的振动消失。连续体源于H5O+2中易极化的氢键，而宽谱带来源于这些基团中的水分子。H5O+2连续谱的吸光度随该基团与其环境(氢键受体的性质、阴离子强度或附加水分子)的相互作用而变化。虽然两种酸的解离行为相似，但CF3SO-3对阴离子的氢键受体强度比ClO-4强得多。
Aqueous perchloric acid and trifluoromethane sulphonic acid solutions have been studied as a function of concentration by i.r. spectroscopy. The degree of dissociation was determined from the absorbance of bands characteristic of the acid molecules. Easily polarizable hydrogen bonds are indicated by i.r. continua. In highly concentrated solutions (water: acid ratio n < 1) easily polarizable acid–water hydrogen bonds AH [graphic omitted] OH2⇌ A– [graphic omitted] H+OH2 are formed. The weights of the proton limiting structures demonstrate that the energy surface for these hydrogen bonds is an asymmetric double minimum with the deeper well at the water molecule. The vibrations of the water molecules are strongly influenced by the proton, i.e., they have more or less H3O+ character. With increasing n, complete dissociation occurs at n= 1.8 (HCIO4) or n= 1.6 (CF3SO3H). First, the weight of proton limiting structure II increases; then H5O+2 is formed and vibrations with H3O+ character vanish. The continuum stems from the easily polarizable hydrogen bond in H5O+2 and the broad bands originate in the water molecules in these groupings. The absorbance of the H5O+2 continuum changes with the interaction of this group with its environment (nature of hydrogen bond acceptors strength of anions or additional water molecules). While the dissociation behaviour of both acids is similar, the hydrogen bond acceptor strength of the anions is much stronger with CF3SO–3 than with ClO–4.