THE DISSOCIATION CONSTANTS OF SOME ALKYL AND ACYL HYDROPEROXIDES
THE DISSOCIATION CONSTANTS OF SOME ALKYL AND ACYL HYDROPEROXIDES
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DOI：
10.1039/tf9534900410
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发表时间：
1953-01-01
影响因子：
--
通讯作者：
MINKOFF, GJ
中科院分区：
文献类型：
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作者：
EVERETT, AJ;MINKOFF, GJ
用电位滴定法测定了有机过酸的解离常数；它们在pK 7-8的范围内。U.-v。氢过氧化物的吸收光谱用于评估其（经典）解离常数，其对数介于11-5和12.8之间。这些数据与通常归因于过氧化物的结构一致。然而，在过氧化物系列中，甲基取代的作用比通常要小：其原因根据Walsh的过氧化物键理论进行了讨论。众所周知，有机过氧化物在碱中溶解时会形成盐，但在文献中（但见表2的脚注）没有表明它们比过氧化氢更弱还是更强。这种化合物的解离常数在1912年由乔伊纳测出，最近由埃文斯和乌里测出；后两位作者对介质的离子强度作了修正，并研究了温度的影响。20”处pK修正值为11.75。由于甲基的诱导作用，可以预期有机过氧化物会弱一些。另一方面，过酸盐有羰基键，这应该会增加酸强度。现有的唯一证据是一份未经证实的报告，即有机过氧化物的强度与硫酸一样（Emte，私人通讯）。鉴于过氧化物的结构，这似乎是不可能的。因此，决定测量相关的pK，看看是否可以根据已知的电子效应来解释观察到的效应，或者是否应该修改某些过酸盐的结构式。由于此目的所需的精度满足了极限：0-1单位pK，因此没有对活度或离子强度进行修正。正如Evans和Uri所示，后一种修正的幅度与我们预期的误差相同。
The dissociation constants of organic peracids have been determined by potentiometric titrations; they lie in the range of pK 7-8. U.-v. absorption spectra of hydroperoxides were used to assess their (classical) dissociation constants, the logarithms of which lie between 11-5 and 12.8. These data agree with the structure generally ascribed to the peracids. In the peroxide series, however, methyl substitution has less effect than usual: the reasons for this are discussed in terms of Walsh's theory of the peroxide bond.It is well known that organic peroxides form salts when dissolved in alkali, but there is no indication in the literature (but see footnote to table 2) as to whether they are weaker or stronger than hydrogen peroxide. The dissociation constant of this compound has been measured by Joyner 1 in 1912, and more recently by Evans and Uri; 2 the latter authors made corrections for ionic strength of the medium, and investigated the effect of temperature. The corrected value of pK was 11.75 at 20". Owing to the inductive effect of the methyl groups it would be expected that the organic peroxides would be somewhat weaker. The peracids, on the other hand, have a carbonyl bond, which should increase the acid strength. The only evidence which was available was an unconfirmed report that the organic peracids were as strong as sulphuric acid (Emte, private communication). This did not seem probable, in view of the structure of the peracids. It was therefore decided to measure the relevant pK's and to see whether the observed effects could be accounted for on the basis of known electronic effects, or whether the structural formulae of some peracids should be revised. As the accuracy required for this purpose was satisfied by the limits If: 0-1 unit of pK, no correction was made for activity or for ionic strength. As shown by Evans and Uri, the magnitude of the latter correction was of the same order as our expected error.