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Lithium C1–C12 n‑Alkanoates: Thermal Behavior from −30 °C to 600 °C

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journal contribution
posted on 2016-02-19, 11:59 authored by Huong Ly Bui, Arno de Klerk
The lithium C1–C12 n-alkanoates (Li-carboxylates) were synthesized, and their thermal behavior was studied over the temperature range t/°C = (−30 to 600). Infrared and Raman spectroscopy indicated that the C3–C12 Li-carboxylates exist in two different configurations and that these configurations persisted after melting. In both configurations the equivalence of the C–O bonds were retained. Evidence for covalent character of the Li–O bond was found only for lithium methanoate. Solid–solid phase transitions were observed for all C1–C12 Li-carboxylates, with the exception of lithium butanoate, hexanoate, and octanoate. No liquid crystal phases were found for any of the C1–C12 Li-carboxylates. These observations were consistent with literature. A previously unreported solid–solid transition at temperature t/°C = (41.3 ± 0.3) with enthalpy ΔH/kJ·kg–1 = (2.8 ± 0.1) was observed for lithium dodecanoate. The melting points of the C1–C2 Li-carboxylates were t/°C = (272 and 283) respectively. For the other Li-carboxylates, the melting points decreased monotonically from t/°C = (331) for lithium propanoate, to t/°C = (227) for lithium dodecanoate. The experimental values for melting point temperature and enthalpy of melting were consistent with literature. Thermal decomposition produced lithium carbonate (Li2CO3) as solid residue and took place at t/°C = (380 to 390) for C1–C2 Li-carboxylates and t/°C = (450 to 485) for C3–C12 Li-carboxylates.