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首页> 外文期刊>The Journal of Organic Chemistry >Polycyano derivatives of some organic tri- and hexacyclic molecules are powerful super- and hyperacids in the gas phase and DMSO: Computational study by DFT approach
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Polycyano derivatives of some organic tri- and hexacyclic molecules are powerful super- and hyperacids in the gas phase and DMSO: Computational study by DFT approach

机译：一些有机三环和六环分子的多氰基衍生物在气相和DMSO中是强酸和高酸：DFT方法的计算研究

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摘要

B3LYP/6-311+G(2df,p)//B3LYP/6-31+G(d) calculations convincingly show that tricyclic organic compounds 1 and 2 offer scaffolds suitable for tailoring powerful neutral organic acids. Their cyanation at all C(sp~2)-H positions provide superacids as evidenced by their enthalpies of deprotonation ΔH_(acid)(1b_(CN)) = 257.2 and ΔH _(acid)(2b_(CN)) = 250.9 kcal mol~(-1), which are close to the threshold of hyperacidity of 245 kcal mol~(-1). On the other hand hexacyclic system 3 cyanated at all possible substitution sites along the perimeter except the acidic C(sp~3)-H position provides a true hyperacid with ΔH_(acid)(3a_(CN)) = 242.8 kcal mol ~(-1). The reason behind the dramatic acidifying effect is a vigorous anionic resonance effect in the corresponding conjugate bases assisted by a cooperative substituent effect of the CN groups. It is convincingly shown that compounds 1 and 2 represent rigid antiaromatic quasi-[12]annulene and aromatic quasi-[14]annulene par excellence, respectively, conforming to Hückel's (4n + 2)π electron count rule in the bridged polycyclic systems. Calculations of the pK_a values in DMSO show that the polycyano derivatives are powerful superacids in solutions too.
机译：B3LYP / 6-311 + G（2df，p）// B3LYP / 6-31 + G（d）的计算令人信服地表明，三环有机化合物1和2提供了适合剪裁强力中性有机酸的支架。它们在所有C（sp〜2）-H位置的氰化反应提供了超强酸，其去质子化焓为ΔH_（酸）（1b_（CN））= 257.2和ΔH_（酸）（2b_（CN））= 250.9 kcal mol 〜（-1），接近于245 kcal mol〜（-1）的高酸度阈值。另一方面，六价环系3在除酸性C（sp〜3）-H位置以外的所有可能的取代位置处氰化，提供了真正的高酸，ΔH_（acid）（3a_（CN））= 242.8 kcal mol〜（- 1）。显着的酸化作用背后的原因是在相应的共轭碱中剧烈的阴离子共振作用，并由CN基团的协同取代作用所辅助。令人信服地表明，化合物1和2分别代表优异的刚性抗芳族准[12]环戊烯和芳族准[[14]环戊烯]，符合桥联多环系统中的Hückel（4n + 2）π电子计数规则。 DMSO中pK_a值的计算表明，多氰基衍生物在溶液中也是强大的超酸。

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