Polymorphs of oxindole as the core structures in bioactive compounds

Abstract

A new polymorph of oxindole (termed as “δ-form”) has been found and characterized by single-crystal X-ray diffraction.

Solubility Measurement and Correlation of 2-Oxindole in 12 Pure Organic Solvents

“…However, in the rest of the solvents [1-propanol (Figure d), 2-propanol (Figure e), DCM (Figure g), EtOAc (Figure i) and acetonitrile (Figure j)], the characteristic peaks at 17° and 26° are very weak whereas other characteristic peaks at 15° and 23° become stronger, which means another polymorph is obtained. After searching the literature, we found that this phenomenon had been reported . There are four polymorphs for 2-oxindole, that is, α, β, γ, and δ.…”

“…After searching the literature, we found that this phenomenon had been reported. 35 There are four polymorphs for 2-oxindole, that is, α, β, γ, and δ. As Hachuła et al had pointed, 35 the α-form was the most available form and the β-form is the most theoretically stable form.…”

“…35 There are four polymorphs for 2-oxindole, that is, α, β, γ, and δ. As Hachuła et al had pointed, 35 the α-form was the most available form and the β-form is the most theoretically stable form. They obtained the δ-form only once when cooling crystallization in pure ethanol.…”

“…By the way, there are only two parameters in the λh equation, in which λ and h are always considered to relate to the nonideality and enthalpy of the solution. 35 The fact that the λ value ranges from 0.06 to 2.91 demonstrated that the solutions are far from ideal. The APRD of the λh equation is from 0.39 to 5.39%, which means that this equation could correlate the solubility data with acceptable results.…”

“…As stated above, the Δ p and Δ C p are neglected, which might result in a less correlation result. By the way, there are only two parameters in the λ h equation, in which λ and h are always considered to relate to the nonideality and enthalpy of the solution . The fact that the λ value ranges from 0.06 to 2.91 demonstrated that the solutions are far from ideal.…”