10.1021/jp200760p.s001 Fuwei Pi Fuwei Pi Fumitoshi Kaneko Fumitoshi Kaneko Makio Iwahashi Makio Iwahashi Masao Suzuki Masao Suzuki Yukihiro Ozaki Yukihiro Ozaki Solid-State Low Temperature → Middle Temperature Phase Transition of Linoleic Acid Studied by FTIR Spectroscopy American Chemical Society 2011 transition MT FTIR progression bands LT linoleic acid CH 2 group 2011-05-19 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Solid_State_Low_Temperature_Middle_Temperature_Phase_Transition_of_Linoleic_Acid_Studied_by_FTIR_Spectroscopy/2651335 Temperature-dependent FTIR spectra of linoleic acid were measured over a temperature range of −80 to −30 °C to explore solid-state low-temperature (LT) → middle-temperature (MT) phase transition of linoleic acid. Band assignments were made mainly for the 900–760 cm<sup>–1</sup> region, where the bands due to <i>cis</i>-olefin group’s C–H out-of-plane mode and the progression bands due to CH<sub>2</sub> rocking–CH<sub>2</sub> twisting modes are expected to appear. The structural evolutions during the LT → MT phase transition of linoleic acid were investigated by analyzing the progression bands with the simple-coupled oscillator model to elucidate the features of acyl chain influenced with two <i>cis</i>-CC bonds linked through one CH<sub>2</sub> group. Structure changes in the LT → MT transition of linoleic acid were compared with those in the γ → α transition of oleic acid. It has been found that the former is rather localized around the <i>cis</i>-diene group, while the latter occurs in the larger portion between the <i>cis</i>-olefin group to the methyl end. It is also suggested that the conformational change in the <i>cis</i>-olefin group on the LT → MT transition is on a lesser scale than that on the γ → α transition.