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1 结构特征分析正卤酸的化学式可表示为HORO_2,其结构为:,卤素原子采用SP~3杂化,形成一种变形的四面体结构。其中羟基氧一个,非羟基氧两个,电子偏离表示为:由于同卤素R成键的非羟基氧有两个,使分子中电子偏移程度较大,H—O极性较强,易离解出H~+,故所有卤酸均为强酸。又因原子半径ClBr>I,根据Pauling规则,中心原子R对H—O吸引电子能力的强弱顺序为HClO_3>HBrO_3>HIO_3,造成酸强度顺序为HClO_3>HBrO_3>HIO_3。氢卤酸结构式为H—R,在水中电离时,酸强度主要决定于H—R键能和R的电子亲合能。H—R键越弱,越易释放出H~+;亲合能越大,HR分子极性越大,在水中越易电离。由氢卤酸的键能、电子亲合能数据可知,H—R键能相差较大,而电子亲合能较接近,故键能对HR的电离的影响是主要的,使得从HF→HCl→HBr→HI电离能力逐渐增强,酸性增强。
Structure analysis The chemical formula of the orthohalogen acid can be expressed as HORO_2, its structure is: the halogen atom adopts SP 3 hybridization, forming a deformed tetrahedron structure. One of the hydroxyl oxygen, two non-hydroxy oxygen, electronic deviation is expressed as: with the halogen R bonding non-hydroxy oxygen there are two, so that the molecular electronic migration greater degree of H-O polarity is strong, easy to dissociate H ~ +, so all halogen acid are strong acid. Due to the atomic radius Cl
Br> I, according to Pauling’s rule, the order of the central atom R to H-O attracting electrons is HClO_3> HBrO_3> HIO_3, HClO_3> HBrO_3> HIO_3. Hydrohalic acid structural formula H-R, ionization in water, the acid strength mainly depends on the H-R bond and R electron affinity. H-R bond is weaker, the more easy to release H ~ +; Affinity, the greater the polarity of HR molecules, the more easily ionized in the water. From the bond energies and electron affinity data of hydrohalic acid, it can be seen that the H-R bonds can be quite different and the electron affinity is close, so the influence of bond energy on the ionization of HR is the main one, → HBr → HI Ionization capacity gradually increased, acidity increased.
Br> I, according to Pauling’s rule, the order of the central atom R to H-O attracting electrons is HClO_3> HBrO_3> HIO_3, HClO_3> HBrO_3> HIO_3. Hydrohalic acid structural formula H-R, ionization in water, the acid strength mainly depends on the H-R bond and R electron affinity. H-R bond is weaker, the more easy to release H ~ +; Affinity, the greater the polarity of HR molecules, the more easily ionized in the water. From the bond energies and electron affinity data of hydrohalic acid, it can be seen that the H-R bonds can be quite different and the electron affinity is close, so the influence of bond energy on the ionization of HR is the main one, → HBr → HI Ionization capacity gradually increased, acidity increased.