Observation of aliphatic C-H X hydrogen bonds in imidazolium ionic liquidsElectronic supplementary information (ESI) available: Details regarding the synthesis of the sequentially deuterated [C4mim]PF6 and [C4mim]BF4 isotopologues and the preparation of the IL samples used in the NMR experiments, and 1H, 19F, 31P, and 11B NMR data employed in all the Δ(H,D) estimations. See DOI: 10.1039/c4cc09783a

Measurement of H/D isotope effects on the 19 F resonances of sequentially deuterated 1- n -butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate isotopologues reveals the formation of aliphatic C-H X hydrogen bonds between the fluorinated anions and protons along the N -alkyl sidechains of the cations. Measurement of H/D isotope effects on the 19 F resonances of sequentially deuterated 1- n -butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate isotopologues reveals the formation of aliphatic C-H X hydrogen bonds between the fluorinated anions and protons along the N -alkyl sidechains of the cations.