I do not play poker,‡ and so I had to look up a 5-4-3-2-1(A), which Wikipedia informs me is a 5-high straight flush, also apparently known as a steel wheel. In previous posts I have suggested acids which can be ionised by (probably) 5, 4, 3 or 1 discrete water molecules in the gas phase; now to try to track down a candidate for ionisation by the required two water molecules to form that straight flush.
As the counter-anion to quaternary ammonium cations, bis(trifluoromethylsulfonyl)imide is a component of some ionic liquids. Its conjugate acid is thought[cite]10.1524/zkri.1998.213.4.217[/cite],[cite]10.5517/CC3ZYWW[/cite] to protonate on the nitrogen.
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My first obvious attempt was to place two waters near that N-H to see if it would ionise from that position.[cite]10.14469/ch/191136[/cite] The proton remains attached to the nitrogen(-:
Next, how about re-locating the waters so that they are closer to the sulfonyl oxygens? This time we do have the characteristic hydronium cation forming.[cite]10.14469/ch/191137[/cite] However, the free energy of this isomer is +6.7 kcal/mol higher relative to the NH form. So not a 5-high straight flush in a strict sense, but it perhaps does give a hint of how one might design the missing card.
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‡Confession time. I did spend many a Wednesday afternoon as an undergraduate playing the card game bridge.
Tags: free energy, gas phase, steel wheel