Different packing in three polymorphs of 2,4,6-trimethoxy-1,3,5-triazine

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Polymorphism is a critical phenomenon influencing the physical and chemical properties of crystalline materials.
• Understanding different solid forms is essential for controlling material behavior in various applications.

Purpose of the Study:

• To investigate and characterize the polymorphic forms of 2,4,6-trimethoxy-1,3,5-triazine.
• To determine the crystallographic and thermodynamic properties of each polymorph.

Main Methods:

• X-ray diffraction analysis to determine crystal structures.
• Differential scanning calorimetry (DSC) to study phase transitions and melting points.
• Crystallization from various solvents to isolate different polymorphs.

Main Results:

• Identified three polymorphs: alpha (orthorhombic, Pnma), beta (monoclinic, P2(1)), and gamma (trigonal, R3c).
• Determined phase transition temperature (340 K) and enthalpy (3.9 kJ mol(-1)) between alpha and beta polymorphs.
• Measured heats of fusion for beta (18.1 kJ mol(-1) at 404 K) and gamma (11.4 kJ mol(-1) at 409 K) polymorphs.
• Confirmed planar molecular geometry across all polymorphs, with differences attributed to molecular packing.

Conclusions:

• 2,4,6-trimethoxy-1,3,5-triazine displays rich polymorphism with distinct crystalline arrangements.
• The observed polymorphism offers opportunities for tuning material properties through controlled crystallization and phase selection.