Fridman Natalya, Kapon Moshe, Sheynin Yana, Kaftory Menahem
Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Acta Crystallogr B. 2004 Feb;60(Pt 1):97-102. doi: 10.1107/S0108768103026284. Epub 2004 Jan 21.
2,4,6-trimethoxy-1,3,5-triazine was found to exhibit three different polymorphs. The alpha-polymorph undergoes reversible phase transformation to the beta-polymorph at 340 K with an enthalpy of 3.9 kJ mol(-1). The heat of fusion of the beta-polymorph at 404 K is 18.1 kJ mol(-1). The low-temperature phase (alpha-polymorph) crystallizes in the orthorhombic space group Pnma. The high-temperature phase (beta-polymorph) can be obtained from the melt and crystallizes in the monoclinic space group P2(1). The gamma-polymorph is obtained by crystallization from a 1:1 mixture of methanol and methylenechloride from hydrolyzed 2,4-dimethoxy-6-oxybenzophenone-1,3,5-triazine. The gamma-polymorph melts at 409 K with an enthalpy of 11.4 kJ mol(-1). The gamma-polymorph crystallizes in the trigonal space group R3c. The molecules occupy a crystallographic threefold axis. Molecules of 2,4,6-trimethoxy-1,3,5-triazine are planar in all three polymorphs. The major difference between the three polymorphs is the mode of packing of the molecules in the crystal.
发现2,4,6 - 三甲氧基 - 1,3,5 - 三嗪呈现出三种不同的多晶型物。α - 多晶型物在340 K时会发生可逆的相转变成为β - 多晶型物，焓变为3.9 kJ mol⁻¹。β - 多晶型物在404 K时的熔化热为18.1 kJ mol⁻¹。低温相（α - 多晶型物）在正交晶系空间群Pnma中结晶。高温相（β - 多晶型物）可从熔体中获得，并在单斜晶系空间群P2(1)中结晶。γ - 多晶型物是由水解的2,4 - 二甲氧基 - 6 - 氧基二苯甲酮 - 1,3,5 - 三嗪在甲醇和二氯甲烷的1:1混合物中结晶得到。γ - 多晶型物在409 K时熔化，焓为11.4 kJ mol⁻¹。γ - 多晶型物在三方晶系空间群R3c中结晶。分子占据一个晶体学三重轴。2,4,6 - 三甲氧基 - 1,3,5 - 三嗪的分子在所有三种多晶型物中都是平面的。这三种多晶型物之间的主要区别在于晶体中分子的堆积方式。
