Isothermal titration calorimetry (ITC) and potentiometric titration (PT) methods were used to study the interactions of cobalt(II) and nickel(II) ions with buffer substances 2-(N-morpholino)ethanesulfonic acid (Mes), dimethylarsenic acid (Caco), and piperazine-N,N 0 -bis (2-ethanesulfonic acid) (Pipes). Based on the results of PT data, the stability constants were calculated for the metal-buffer complexes (T = 298.15 K, ionic strength I = 100 mM NaClO 4 ). Furthermore, calorimetric measurements (ITC) were run in 100 mM Mes, Caco, and Pipes solutions with pH 6, at 298.15 K. The enthalpies (DH) of the metalbuffer complexation reactions were calculated indirectly by displacement titration using nitrilotriacetic acid (H 3 NTA) as a strong-binding, competitive ligand. Finally, to verify obtained results, the number of protons released by H 3 NTA due to complexation of the cobalt(II) and nickel(II) ions was determined from calorimetric data and compared with results of calculations.
Benzotriazole ( BtH) reacts easily with aliphatic primary amines and formaldehyde in aqueous media to give one or more of three types of product: (i) (BtCH,),NR(5), (ii) (BtCH,NR),CH, (6), and/or (iii) BtCH,NHR (7). The product formed depends on the molar ratio of the substrates, and on the degree of steric hindrance in the amine, and is also influenced by the nature of the solvent. Primary aliphatic 1,2or 1,3-diamines yield cyclic aminals which are imidazolidine (8a) and hexahydropyrimidine (8b) derivatives. Reactions of these aminals with Grignard reagents, and with cyanide anion as nucleophiles, are also described.
Eine neue Methode zur N‐Alkylierung von Imidazolen und Benzimidazolen
Die N‐Alkylierung von Imidazolen und Benzimidazolen in Zwei‐Phasen‐Systemen (flüssig/flüssig und flüssig/fest) wird beschrieben.
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