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The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
According to calculations, ortho-diethynylbenzene dianion is the strongest superbase and has a proton affinity of 1,843.987 kJ/mol (440.723 kcal/mol). [1] The meta isomer is the second-strongest, and the para isomer is the third. All three are readily able to accept any proton to its ethynyl tails, from almost any compound.
The aromatization of an additional ring in 4,12-Dihydrogen-4,8,12-triazatriangulene is utilized by Al-Yassiri and Puchta to get a representative for a new class of Δ-shaped proton sponges. [8] This compound has a calculated proton affinity of 254 kcal/mol (B3LYP/6-311+G**) and is therefore between 1,8-Bis(dimethylamino)naphthalene and HMPN.
It was the strongest known base until 2008, when the isomeric diethynylbenzene dianions were determined to have a higher proton affinity. The methanide ion CH − 3 was the strongest known base before lithium monoxide anion was discovered. [2] LiO − has a proton affinity of ~1782 kJ/mol. [3]
Proton affinity: a measure of basicity in the gas phase. Stability constants of complexes: formation of a complex can often be seen as a competition between proton and metal ion for a ligand, which is the product of dissociation of an acid.
For a proton transfer reaction, this is just the difference in proton affinity between the neutral reagent molecule and the neutral analyte molecule. [8] This results in significantly less fragmentation than does 70 eV electron ionization (EI). The following reactions are possible with methane as the reagent gas.
The electron affinity of molecules is a complicated function of their electronic structure. For instance the electron affinity for benzene is negative, as is that of naphthalene, while those of anthracene, phenanthrene and pyrene are positive. In silico experiments show that the electron affinity of hexacyanobenzene surpasses that of fullerene. [5]
If the mobile phase contains solvents with a higher proton affinity than water, proton-transfer reactions take place that lead to protonated the solvent with higher proton affinity. For example, when methanol solvent is present, the cluster solvent ions would be CH 3 OH 2 + (H 2 O) n (CH 3 OH) m. [2] Fragmentation does not normally occur inside ...