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Synthesis, structure and proton conductivity of 2,4,5-trimethylbenzenesulfonic acid dihydrate

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Abstract

2,4,5-Trimethylbenzenesulfonic acid dihydrate was isolated in the monocrystalline state. Crystal and molecular structures of the compound were determined by X-ray diffraction analysis and vibrational spectroscopy. The compound crystal system is monoclinic: a =7.7445(3) Å, b = 7.5360(3) Å, c = 9.9477(4) Å, α = γ = 90°, β = 92.123(4)°, V = 580.17(4) Å3, P21, Z = 2, R1 = 0.0323, dcalc. = 1.353 g cm−3, T = 150 K. A 2D hydrogen bond network formed of a dioxonium ion and oxygen atom of a sulfogroup was identified in the crystal structure. IR absorption spectra, Raman spectra and ATR IR spectra of 2,4,5-trimethylbenzenesulfonic acid dihydrate and deuterodihydrate have been obtained in the region 50–4000 cm−1. It was found that the proton and deuterium in the H5O2+ and D5O2+ cations shifted from the midpoint of the strong hydrogen bond toward one of two water molecules according to the scheme O⋯H+⋯O → O⋯H+–O and O⋯D+⋯O → O⋯D+–O. Spectroscopic data concerning dioxonium ion formation show satisfactory agreement with X-ray diffraction analysis. The effect of environment humidity on the state of 2,4,5-trimethylbenzenesulfonic acid dihydrate aggregation was investigated. It was shown that the number of water molecules increases up to 2.5 per sulfogroup in the 7–84 rel.% air humidity interval through additional water molecules adsorption. A further humidity increase led to compound deliquescence. The proton conductivity as measured by impedance spectroscopy is 10−9–10−5 S cm−1 in the 7–58 rel.% humidity interval at 298 K with a [H2O]/[SO3] = 2.2 ratio at maximum conductivity.

Graphical abstract: Synthesis, structure and proton conductivity of 2,4,5-trimethylbenzenesulfonic acid dihydrate

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Publication details

The article was received on 21 Dec 2017, accepted on 02 Apr 2018 and first published on 04 Apr 2018


Article type: Paper
DOI: 10.1039/C7NJ05068B
Citation: New J. Chem., 2018, Advance Article
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    Synthesis, structure and proton conductivity of 2,4,5-trimethylbenzenesulfonic acid dihydrate

    A. V. Pisareva, G. V. Shilov, A. I. Karelin, R. V. Pisarev, I. A. Shilova, Y. A. Dobrovolsky and S. M. Aldoshin, New J. Chem., 2018, Advance Article , DOI: 10.1039/C7NJ05068B

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