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在25°及0.10M高氯酸鈉存在下,N-环己烷氨基乙酸(CyG)和N-β-萘氨基乙酸 (βNG)在30％(体积)乙醇中的表观离解常数用pH法測定为:CyG:pK_(COOH)=2.70,pK_(R_2NH_2~+)=9.83;βNG:pK_(COOH)=2.26,pX_(R_2NH_2~+)=4.46。前者(CyG)的酸碱強度均与氨基乙酸(G)的相似,但后者(βNG)的碱性却小于其异构体N-α-萘氨基乙酸(αNG)的碱性約百万倍,而与N-苯氨基乙酸(φG)的碱性相似。这进一步說明αNG上的8位氫原子和1位上羧甲氨基之間的空間效应是导致其碱性增強的主要原因。βNG的酸性較αNG略強,可能是在共軛程度較高的βNG分子中,N的电子密度較低的β-萘氨基对于羧基所产生較大的誘导效应之結果。
Apparent dissociation constants of N-cyclohexanecarboxylic acid (CyG) and N-β-naphthylaminoacetic acid (βNG) in 30% by volume of ethanol in the presence of sodium perchlorate at 25 ° and 0.10 M were determined by the pH method The results were as follows: CyG: pK COOH = 2.70, pK R 2 NH 2 + = 9.83; βNG pK COOH 2.26 pX R 2 NH 2 + 4.46. The former (CyG) has similar acid-base strength to glycine (G) but the latter (βNG) is less basic than its basic N-α-naphthylaminoacetic acid (αNG) , But similar to that of N-phenylaminoacetic acid (φG). This further indicates that the steric effect between the 8-position hydrogen atom on the αNG and the carboxymethylamino group at the 1 position is the main reason for the increase in its basicity. The acidity of βNG is slightly stronger than that of αNG, which may be the result of the greater inducing effect of β-naphthylanine with lower electron density on the carboxyl group in βNG molecules with higher degree of conjugation.