*2.3. Synthesis and Characterization of Venetoclax Hydrate*

Venetoclax (100 mg) was placed into an Erlenmeyer flask and 100 mL of ACN-NH4HCO<sup>3</sup> (10 mM solution) = 8:2 solvent mixture was added. The obtained suspension was sonicated in an ultrasonic bath for 5 minutes. The obtained turbid solution was left to stand at ambient temperature for 2 hours and then filtered through a polytetrafluoroethylene (PTFE) filter. The obtained yellow solution was placed into a glass laboratory bottle and left to stand unclosed at ambient temperature for 60 days. During this time, the solvent evaporated affording agglomerated crystals on the bottom of the bottle and needle-shaped crystals that were deposited on the walls of the glass bottle. The agglomerated crystals on the bottom of the glass bottle were discarded while the needle-like crystals suitable for the single crystal X-ray analysis obtained from the walls of the glass bottle were collected for further analysis. DSC (10 ◦K/min): 49 ◦C onset, 64 ◦C peak (endothermic transition) and 168 ◦C onset, 182 ◦C peak (endothermic transition); ATR-FTIR: 565, 663, 734, 760, 816, 831, 865, 902, 985, 1098, 1125, 1141, 1171, 1231, 1244, 1255, 1346, 1410, 1434, 1521, 1569, 1578, 1607, 1677, 2842, 2917, 3303, 3364 cm−<sup>1</sup> ; Raman: 796, 838, 1068, 1142, 1161, 1172, 1232, 1272, 1363, 1427, 1496, 1607, 1678, 2847, 2892, 2919, 2941, 2961, 3065, 3083 cm−<sup>1</sup> ; *p*-XRD (Cu-Kα): 6.5, 7.0, 7.7, 9.8, 10.8, 11.4, 11.7, 12.6, 13.1, 14.3, 15.6, 16.7, 16.8, 17.3, 17.7, 18.2, 18.5, 19.9, 20.0, 20.5, 21.4, 21.9, 22.5, 23.0, 23.4, 24.3, 24.9, 26.1, 26.4, 28.7, 29.2, 29.5◦ 2θ.
