Abstract
In this work, we have determined the structures of lithium methanesulfonate, Li(CH3SO3), and potassium methanesulfonate, K(CH3SO3), and analysed their vibrational spectra. The lithium salt crystallizes in the monoclinic space group C2/m with two formula units in the primitive cell. The potassium salt is more complex, crystallizing in I4/m with 12 formula units in the primitive cell. The lithium ion is fourfold coordinated in a distorted tetrahedron, while the potassium salt exhibits three types of coordination: six-, seven- and ninefold. Vibrational spectroscopy of the compounds (including the 6Li and 7Li isotopomers) confirms that the correlation previously found, that in the infrared spectra there is a clear distinction between coordinated and not coordinated forms of the methanesulfonate ion, is also valid here. The lithium salt shows a clear splitting of the asymmetric S–O stretch mode, indicating a bonding interaction, while there is no splitting in the spectrum of the potassium salt, consistent with a purely ionic material.
Highlights
Derivatives of methanesulfonic acid, CH3SO3H, which are known as mesylates, occur widely in chemistry as esters or salts
We have previously investigated the vibrational spectroscopy of the parent acid, methanesulfonic acid [11] and some of its salts, M = Na, Cs, Cu, Ag, Cd [12]
The structures of the lithium and potassium salts of methanesulfonic acid have been previously determined; as far as we are aware, neither has been deposited in a recognized database, Figure 1
Summary
Derivatives of methanesulfonic acid, CH3SO3H, which are known as mesylates, occur widely in chemistry as esters or salts. Some of the organic derivatives are important biologically This arises because mesylate is a good leaving group in nucleophilic substitution reactions as a result of the efficient delocalization of negative charge between the three oxygen atoms. Metal methanesulfonate salts (M[CH3SO3]x, e.g. M = Na, K, Mg, Ca) occur naturally via the oxidation of 2 dimethyl sulfide and subsequent reaction with the cations present in the ocean [4]. These may act as condensation nuclei for clouds [5,6]. We examine the lithium and potassium methanesulfonate salts to further test the correlation. As a prerequisite to this, we have determined the crystal structures of the compounds
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