Measurement of octanol–air and air–water partition coefficients of isopropyl and isobutyl nitrate

Abstract

This work provides the first experimental determination of Henry's law solubility constants (H^cp_S ≡ H) in n-octanol (H_oct) for isopropyl and isobutyl nitrate (IPN and IBN) over the 284.65 K to 309.65 K temperature (T) range. The H constants were measured by dynamic gas stripping using a bubble column apparatus and gas chromatography with electron capture detection (GC-ECD). The H_oct data are best described by ln(H^cp_S(IPN)_oct/[M atm⁻¹]) = −(10.60 ± 1.54) + (4214 ± 459)/T and ln(H^cp_S(IBN)_oct/[M atm⁻¹]) = −(12.01 ± 0.85) + (4937 ± 253)/T, where T is in kelvin. In addition, their H constants in deionized water (H_aq) were measured to corroborate literature H_aq values. The H_aq and H_oct data were combined to calculate octanol–water partition coefficients (K_OW = H_oct/H_aq), obtaining average values of (33 ± 5) for IPN and (1.3 ± 0.1) × 10² for IBN. The experimental data were compared to predictions of H_oct, H_aq and K_OW by structure–activity relationship models (SARs).