On Frank Weinhold

20 March 2015 - Controversy

Frank Weinhold is Professor Emeritus at the University of Wisconsin. A chemist with a talent for attracting controversy so it seems. He recently found himself in hot scientific debate on two occasions. Last year together with Roger Klein, Weinhold introduced the concept of the "anti-electrostatic hydrogen Bond" (AEHB) (DOI). Is the well-known hydrogen-bond purely based on an electrostatic attraction? (accepted theory) or is something else going on? The alternative AEHB theory claims that a short-range donor-acceptor covalent interaction between two atoms of same charge outperforms the long-range electrostatic repulsion between them. This theory was tested by Weinhold on a hypothetical hydrogen bond between a fluoride (donor) and a bicarbonate anion (acceptor) and calculations did confirm an attractive interaction. According to Weinhold The AEHB bond can be found in other ionic interactions.

Controversial?. Frenking and Caramori represent the members of the opposition. In their comment (DOI) they argue that "it takes much chutzpah to use an energy-minimum structure with a well depth of 0.05(!) kcal per mol" to identify a bond and "it takes a still higher degree of flippancy when the electrostatic interactions between the fragments are estimated with a formula that was proven already in 1927 not to be suitable for calculating Coulombic forces between atoms at shorter region". They are not done yet when they write that "coulombic interactions are calculated with the correct formula for electronic charges rather than using hand-waiving arguments and a wrong equation". What the dispute of course boils down to is that Weinhold is a natural bond orbital guy and that Frenking lives by energy decomposition analysis

The other debate Weinhold has dragged himself into is all about rabbit ears. In 2014 ( DOI) he argued that the two lone pairs on water are not symmetrical (as per conventional theory, resembling rabbit ears, backed by NBO) but asymmetrical with different degrees of s-p mixing based on symmetry arguments. Not an entirely novel idea , others went before him, so where is the controversy you may ask. Here it is: in a recent comment Hiberty et al. counter that notion (DOI) but in an unusual way. Their research in their words "shows that the equivalent lone-pair picture is an equivalent and a valid alternative to the nonequivalent one; neither is superior to the other or anachronistic with respect to the other". This is totally unconvincing: it is like the Pope and Galilei happily agreeing that "the sun may revolve around earth or earth may revolve around the sun, both views are equally valid". What makes Hiberty say such a thing? Hiberty lives by localized molecular orbitals.

And so who is right? and who is wrong? Depends on your computational beliefs. I do not have any but I do know retired professors are usually right.