Soybean oil was modified in two steps: (1) conjugation of soybean oil and (2) Diels-Alder addition with 3-(trimethoxysilyl) propyl methacrylate, 2,2,2-trifluoroethyl methacrylate and triallyl ether acrylate. The structures were characterized using H-1 NMR, C-13 NMR, C-13-H-1 gradient heteronuclear single quantum coherence (gHSQC) NMR spectroscopy, and MALDI-TOF mass spectrometry. The C-13-H-1 gHSQC NMR spectra helped confirm the formation of a cyclohexene ring in all reactions, indicating a Diels-Alder addition. The diluent efficiency of modified soybean oil was evaluated in long oil alkyd formulation. Triallyl ether functionalized soybean oil resulted in the highest reduction in the viscosity of the alkyd formulations. (c) 2014 Wiley Periodicals, Inc.