Design of Neutral Organic Superacids and Superbases Ex Machina

Zvonimir Maksić 

RUDJER BOSKOVIĆ INSTITUTE, BIJENIČKA C. 54, Zagreb 10 000, Croatia

Abstract

Recent advances in studying Brønsted (organic) superbases and superacids, attained by the modern computational chemistry methods, will be presented. It will appear that, by following a simple strategy developed by us [1], one can tailor a dense ladder of neutral organic superbases up to the proton affinity (PA) of 300 kcal/mol [2-4]. Since the PA of the archetypal DMAN (1,8-bis-dimethylaminonaphthalene) superbase in the gas phase (GP) is 245.7 kcal/mol, it follows that the most powerful designed superbases are stronger by 40 orders of magnitude than the reference compound. Their pKa in acetonitrile is about 50 units implying that they retain superbasic properties in solutions too. Analogously, it is possible to construct a dense scale of organic superacids with ΔHacid as low as 245 kcal/mol in the GP by using a concept of the anionic resonance in deprotonated polycyano substituted hydrocarbons [4-8]. Taking into account that pKa of sulphuric acid (H2SO4) in DMSO is 1.99, it turns out that the designed superacids are stronger by some 40 orders of magnitude than this molecule taken as a standard of superacidity. Some aspects of syntheses of organic superbases and superacids and possible applications will be discussed.

[1] B. Kovačević, Z. B. Maksić, Proceedings of NIC 2004, 20, 71-80.

[2] B. Kovačević, Z. B. Maksić, Chem. Comm. 2006, 1524-1526.

[3] B. Kovačević, Z. B. Maksić, Tetrahedron Lett. 2006, 47, 2553-2555.

[4] Z. B. Maksić, B. Kovačević, Chem. Eur. J. 2002, 8, 1694-1702.

[5] R. Vianello, Z. B. Maksić, Eur. J. Org. Chem. 2004, 5003-5010.

[6] Z. B. Maksić, R. Vianello, Tetrahedron Lett. 2004, 45, 8663-8666.

[7] R. Vianello, J. F. Liebman, Z. B. Maksić, Chem. Eur. J. 2004, 10, 5751-5761.

[8] R. Vianello, Z. B. Maksić, Chem. Comm. 2005, 3412-3414.

 

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Presentation: invited lecture at 18th Conference on Physical Organic Chemistry, Plenary session, by Zvonimir Maksić
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-04-26 09:42
Revised:   2009-06-07 00:44