Formation and characterization of melam, melam hydrate, and a melam-melem adduct.
Formation and characterization of melam, melam hydrate, and a melam-melem adduct.
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DOI：
10.1002/chem.201203340
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发表时间：
2013-02
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影响因子：
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通讯作者：
Eva Wirnhier;Maria B. Mesch;J. Senker;W. Schnick
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文献类型：
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作者：
Eva Wirnhier;Maria B. Mesch;J. Senker;W. Schnick
直到最近，三聚氰胺[C(3)N(3)(NH(2))(2)](2)NH一直被认为是三聚氰胺缩合过程中的短寿命中间体，由于其高反应活性，只能在特殊反应条件下检测到。一种新的合成方法通过在高压灭菌器中使用升高的氨压力，可以更近距离地观察三聚氰胺的形成和冷凝行为。而在450°C和0.2 MPa氨条件下对双氰胺进行热处理可以产生大量的三聚氰胺，在这些条件下长时间处理（9天）可以形成三聚氰胺-melem加合物，从而使人们第一次了解三聚氰胺缩合成melem的过程。三聚氰胺在300℃（24 h）下水热处理得到三聚氰胺水合物，[C(3)N(3)(NH(2))(2)](2)NH⋅2 h (2)O(空间群P2(1)/ C；A =676.84(2), b=1220.28(4), c=1394.24(4) pm；β= 98.372(2)°;V = 1139.28(6)×10(6)点(3);Z=4)，结晶为由几乎平面的三聚氰胺分子组成的层状结构，从而形成椭球状的玫瑰状图案。由此产生的空隙被四个水分子填满，从而形成一个致密的氢键网络。
Until recently, melam, [C(3)N(3)(NH(2))(2)](2)NH, has been regarded as a short-lived intermediate in the condensation process of melamine that is only detectable under special reaction conditions owing to its high reactivity. A new synthetic approach has allowed a closer look at the formation and condensation behavior of melam by using elevated ammonia pressure in autoclaves. Whereas the thermal treatment of dicyandiamide at 450 °C and 0.2 MPa ammonia yielded melam in large amounts, prolonged treatment under these conditions (9 days) led to the formation of a melam-melem adduct, thus enabling the first insight into the condensation process of melam into melem. The hydrothermal treatment of melam at 300 °C (24 h) yields melam hydrate, [C(3)N(3)(NH(2))(2)](2)NH⋅2 H(2)O (space group P2(1)/c; a=676.84(2), b=1220.28(4), c=1394.24(4) pm; β=98.372(2)°; V=1139.28(6)×10(6) pm(3); Z=4), which crystallizes as a layered structure that is composed of almost-planar melam molecules, thereby forming ellipsoidal rosette-like motifs. The resulting voids are filled with four water molecules, thus forming a dense network of hydrogen bonds.