N,N-dialkyl perfluoroalkanesulfonamides: Synthesis, characterization and properties

Twenty derivatives of N,N-dialkyl perfluoroalkanesulfonamides, n-CmF2m + 1SO2NRR′ (m = 1, 2, 4, 6, 8; R, R′ = CH3, CH2CH3 or CH2CH2OCH3), have been prepared and characterized. Their fundamental physicochemical properties, including melting point, density, viscosity and dielectric constant, are determined. The influences of structural variations in both the perfluoroalkyl and alkyl chains on the above properties are extensively studied. Among these N,N-dialkyl perfluoroalkanesulfonamides, 14 compounds are liquid at room temperature, and some of them exhibit low melting points, even lower than −40 °C. The empirical solvent polarity scales for these liquid perfluoroalkanesulfonamides, such as ‘energy of transition’ ET(30) values and Kamlet–Taft solvent parameters (π*, α, β), are also determined by solvatochromic measurements, and show good linear temperature dependence. The ET(30) values are in the range of 45.36–55.19 kcal mol−1 at 25 °C, comparable to those of short chain alcohols. The π* parameters for the compounds containing alkyl chain are in the range of 0.550–0.651 at 25 °C, being a little higher than those of short chain alcohols. All these prepared compounds show strong hydrogen-bond donating ability (α values ranging from 0.865 to 1.204 at 25 °C), comparable to that of short chain alcohols. Meanwhile, those containing alkoxyalkyl chain display strong hydrogen-bond accepting ability (β values ranging from 0.71 to 0.82 at 25 °C), comparable to that of short chain alcohols.

A series of 20 N,N-dialkyl perfluoroalkanesulfonamides, n-CmF2m + 1SO2NRR′ (m = 1, 2, 4, 6, 8; R, R′ = CH3, CH2CH3 or CH2CH2OCH3), are prepared and characterized. The influences of structure variation in both the perfluoroalkyl and alkyl chains on their fundamental physicochemical properties are extensively studied. Some of the liquid perfluoroalkanesulfonamides exhibit low melting points, even being lower than −40 °C. Both the dielectric constants and the empirical solvent polarity scales, such as ET(30) values and Kamlet–Taft solvent parameters (π*, α, β), indicate that these liquid perfluoroalkanesulfonamides show relatively high polarity comparable to that of short chain alcohols.Figure optionsDownload as PowerPoint slideHighlights
► A series of N,N-dialkyl perfluoroalkanesulfonamides were synthesized in high quality and good yields.
► The influences of structure variation on their fundamental physicochemical properties were extensively studied.
► These compounds showed relatively low melting points even lower than −40 °C.
► These compounds showed high polarity comparable to that of short chain alcohols.