Polymorphic Forms of Lamivudine: Characterization, Estimation of Transition Temperature, and Stability Studies by Thermodynamic and Spectroscopic Studies

Table 4

The enthalpy of transition (ΔH(T)), free energy of transition (ΔG(T)), entropy of transition (ΔS(T)), and transition temperature (𝑇_𝑡) of different polymorphic pairs at 25°C and 37°C.

	ΔHtrans (kJ/mol)		ΔGtrans (kJ/mol)		ΔStrans (J/mol)		𝑇𝑡 (K)
	25°C	37°C	25°C	37°C	25°C	37°C	25°C	37°C
Form IL→II	−0.49	−0.72	−0.18	−0.26	−1.05	−1.52	467.6	468.5
Form IIIL→IIIH	−1.26	−1.13	−0.45	−0.41	−2.72	−2.42	464.3	465.8
Form IIIH→II	−4.69	−3.87	−0.57	−0.64	−13.84	−10.83	339.4	340.4