Dissociation constants and structures of glutamic acid and its esters.
Dissociation constants and structures of glutamic acid and its esters.
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DOI：
10.1042/bj0302085
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发表时间：
1936-01-01
影响因子：
4.1
通讯作者：
Neuberger, A
中科院分区：
文献类型：
--
作者：
Neuberger, A
结果在表I中记录了电位测量的结果。第1列给出了针对大气压校正的电势;在第2列中，记录了针对液体接界校正后的电势。在第3栏中，a表示中和度，第4栏中的c给出存在的酸或碱的总浓度。离子强度随KCl的加入而变化。表观解离常数如所述测定;值通常在± 0-01范围内准确。在pK非常低的情况下（谷氨酸和γ-乙基谷氨酸氢盐的pK 1），大空白校正导致误差幅度更高。在γ-乙基谷氨酸氢酯的pK 2和谷氨酸乙酯的pK的情况下，由于水解和/或内酰胺形成，测量也不太可靠。谷氨酸的pK 14值也仅精确到± 0-03，因为离子强度的校正较大。谷氨酸的离解常数。在谷氨酸的解离过程中涉及到几种平衡，有必要对这些平衡作一些详细的考虑。谷氨酸可以被认为是一种三元酸，其最酸性的形式是阳离子。第一步是H+从阳离子上解离，根据三个反应之一：HOOC。CH（NH，+）CH 2。CH2。酷毙了CH（NH3+）CH2。CH 2。COOH+ H+.......（1 a）、a b1
Results. In Table I the results of the potentiometric measurements are recorded. Column 1 gives the potentials corrected for barometric pressure; in column 2 the potentials are recorded after correction for liquid junction. In column 3, a denotes the degree of neutralization, c in column 4 gives the total concentration of the acid or base present. The ionic strength was varied by additionof KCI. The apparent dissociation constants were determined as described; the values are generally accurate within+ 0-01. In the case of a very low pK (pK1 of glutamic acid and of y-ethyl hydrogen glutamate) the large blank correction causes the margin of error to be higher. In the cases ofpK2 of y-ethyl hydrogen glutamate and pK of ethyl glutamate measurements are also less reliable owing to hydrolysis and/or lactam formation. The value of pK14 of glutamic acid is also only accurate+ 0-03, since the correction for ionic strength is larger.DISCuSSION. The dissociation constants of glutamic acid. Several equilibria are involved in the dissociation of glutamic acid and it is necessary to consider these in some detail. Glutamic acid can beregarded as a tribasic acid of which the most acidic form is a cation. The first step consists in the dissociation of H+ from the cation according to one of the three reactions: HOOC. CH (NH,+) CH2. CH2. COOH-OOC. CH (NH3+) CH2. CH2. COOH+ H+.......(1 a), a b1