The chemical compositions of four low-pressure premixed flames of iso-butanol are investigated with an emphasis on assessing the predictive capabilities of an automatically generated combustion chemistry model. This kinetic model had been extensively tested against earlier experimental data [S.S. Merchant, E.F. Zanoelo, R.L. Speth, M.R. Harper, K.M. Van Geem, W.H. Green, Combust. Flame (2013), http://dx.doLorg/10.1016/j.combustflame.2013.04.023.] and also shows impressive capabilities for predicting the new flame data presented here. The new set of data consists of isomer-resolved mole fraction profiles for more than 40 species in each of the four flames and provides a comprehensive benchmark for testing of any combustion chemistry model for iso-butanol. Isomer-specificity is achieved by analyzing flames, which are burner-stabilized at equivalence ratios of phi = 1.0-1.5 and at pressures between 15 and 30 Torr, with molecular-beam mass spectrometry and single-photon ionization by tunable vacuum-ultraviolet synchrotron radiation. Predictions of the C2H4O, C3H6O, and C4H8O enol-aldehyde-ketone isomers are improved compared to the earlier work by Hansen et al. [N. Hansen, M. R. Harper, W. H. Green, Phys. Chem. Chem. Phys. 13 (2011) 20262-20274] on similar n-butanol flames. A reaction path analysis identifies prominent fuel-consumption and oxidation sequences. Almost all of the species mole fraction data reported here are predicted within the measurement uncertainties of a factor of two to three. Some significant differences with previous published models are highlighted. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.