Heating-induced phase transition of bupropion hydrobromide polymorphs

Area of Science:

• Solid-state chemistry
• Materials science
• Pharmaceutical sciences

Background:

• Bupropion hydrobromide exists in two stable polymorphic forms: form I and form II.
• Understanding polymorphic transitions is crucial for drug production and stability.

Purpose of the Study:

• To investigate the crystal phase transition of bupropion hydrobromide.
• To determine the isothermal crystallization kinetics of the phase transition.

Main Methods:

• Thermal analysis (e.g., DSC, TGA)
• X-ray powder diffractometry (XRPD)
• Scanning electron microscopy (SEM)

Main Results:

• Form II of bupropion hydrobromide transforms into form I upon thermal treatment.
• The Avrami exponent (n ≈ 2.0) suggests a one-dimensional nucleation and growth mechanism for the phase transition between 170°C and 190°C.
• Microscopic morphology studies confirmed the 1D growth.
• The activation energy for the phase transition was calculated to be 239.4 kJ/mol, indicating a high energy barrier.

Conclusions:

• Bupropion hydrobromide undergoes a thermally induced phase transition from form II to form I.
• The transition follows a one-dimensional nucleation and growth pathway.
• A substantial energy input is necessary to initiate this polymorphic transformation.