TY - JOUR
T1 - Evidences for a Null Molar Volume Contribution by Hydroxyl Groups in Ammonium Bistriflimide-Based Ionic Liquids
AU - de Ferro, André Mão
AU - Reis, Patrícia M.
AU - Freitas, Adilson A.
AU - Lopes, José N. Canongia
AU - Rebelo, Luís Paulo N.
AU - Shimizu, Karina
AU - Esperança, José M. S. S.
N1 - info:eu-repo/grantAgreement/FCT/5876/147270/PT#
info:eu-repo/grantAgreement/FCT/3599-PPCDT/127013/PT#
The authors thank Fundação para a Ciência e Tecnologia, FCT/MCTES (Portugal) for financial support through Investigator contracts (IF/00355/2012 to J.M.S.S.E. and IF/00621/2015 to P.M.R.), CEEC contracts (IST-ID/93/2018 to A.A.F. and IST-ID/100/2018 to K.S.) and through projects IF/00621/2015, UID/Multi/04551/2013, PTDC/QEQ-EPR/5841/2014, PTDC/QUI-QFI/29527/2017, Lisboa/01/0145/FEDER/028367, PTDC/CTM-CTM/30326/2017 and PTDC/EQU-EQU/32050/2017. This work was also partially supported by the Associate Laboratory for Green Chemistry—LAQV, by the CQE which are financed by national funds from FCT/MCTES (UID/QUI/50006/2019 and UID/QUI/00100/2019, respectively). The NMR spectrometers are part of The National NMR Facility, supported by FCT/MCTES (RECI/BBB-BQB/0230/2012).
PY - 2019/11/14
Y1 - 2019/11/14
N2 - In this work, we report on the thermophysical and transport properties of seven ammonium bistriflimide ionic liquids. Aiming to study the effect of the manipulation of the ammonium cation on distinct properties of ionic liquids, we have considered two sets of bistriflimide-based ionic liquids with (i) three quasi-similar molar weight cations with distinct functional groups, [N2 1 1 3OH]+, [N2 1 1 2O1]+, and [N2 1 1 4]+ (ii) four cations with increasing number of 2-hydroxyethyl groups and/or alkyl side chain, [N2 1 2OH 2OH]+, [N1 2OH 2OH 2OH]+, [N2 2OH 2OH 2OH]+, and [N4 2OH 2OH 2OH]+. The most relevant result is the strong evidence that the replacement of a methyl group by a hydroxymethyl group in the cation has an almost-null contribution to the overall molar volume of the ionic liquid. Molecular dynamics simulations have been performed to explain from a structural perspective the obtained results. Most of the effect comes from the fact that the intrinsic van der Waals volumes of -CH3 and -CH2OH are not that different (14.7 and 17.8 cm3·mol-1); the remainder of the effect comes from the fact that hydrogen bonding between hydroxyl groups or between them and the charged moieties of the ionic liquid can lead to further contractions of the free volume that annuls the modest intrinsic volume contribution of the OH group.
AB - In this work, we report on the thermophysical and transport properties of seven ammonium bistriflimide ionic liquids. Aiming to study the effect of the manipulation of the ammonium cation on distinct properties of ionic liquids, we have considered two sets of bistriflimide-based ionic liquids with (i) three quasi-similar molar weight cations with distinct functional groups, [N2 1 1 3OH]+, [N2 1 1 2O1]+, and [N2 1 1 4]+ (ii) four cations with increasing number of 2-hydroxyethyl groups and/or alkyl side chain, [N2 1 2OH 2OH]+, [N1 2OH 2OH 2OH]+, [N2 2OH 2OH 2OH]+, and [N4 2OH 2OH 2OH]+. The most relevant result is the strong evidence that the replacement of a methyl group by a hydroxymethyl group in the cation has an almost-null contribution to the overall molar volume of the ionic liquid. Molecular dynamics simulations have been performed to explain from a structural perspective the obtained results. Most of the effect comes from the fact that the intrinsic van der Waals volumes of -CH3 and -CH2OH are not that different (14.7 and 17.8 cm3·mol-1); the remainder of the effect comes from the fact that hydrogen bonding between hydroxyl groups or between them and the charged moieties of the ionic liquid can lead to further contractions of the free volume that annuls the modest intrinsic volume contribution of the OH group.
UR - http://www.scopus.com/inward/record.url?scp=85071869902&partnerID=8YFLogxK
U2 - 10.1021/acs.jced.9b00442
DO - 10.1021/acs.jced.9b00442
M3 - Article
AN - SCOPUS:85071869902
VL - 64
SP - 4932
EP - 4945
JO - Journal of Chemical and Engineering Data
JF - Journal of Chemical and Engineering Data
SN - 0021-9568
IS - 11
ER -