Why are Hydrogen Bonds Directional?

Hydrogen Bonds

Directional O...F halogen bonds.

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Hydrogen and halogen bonds are ruled by the same mechanisms.

Hydrogen and halogen bonds are compared on the basis of ab initio calculations performed for complexes linked through these interactions. The Quantum Theory of Atoms in Molecules (QTAIM) and the Natural Bond Orbitals (NBO) method are applied for a deeper understanding of the nature of interactions. Both interactions are ruled by the same effects of hyperconjugation and rehybridization. In gener...

Why are tax-exempt bonds issued at a premium?*

I derive the optimal timing strategy for an investor taking tax gains and losses on tax-exempt bonds (up to a 7% gain over buy-and-hold). I then derive the issuer’s optimal coupon rate, which maximizes the tax benefit for a tax-timing investor (up to a 3.5% gain over issuing at par, potentially more than the cost of issuance itself). All these gains are transfers from the U.S. Treasury to local...

Hydrogen bonds in liquid water are broken only fleetingly.

Although it is widely accepted that the local structure of liquid water has tetrahedral arrangements of molecules ordered by hydrogen bonds, the mechanism by which water molecules switch hydrogen-bonded partners remains unclear. In this mechanism, the role of nonhydrogen-bonded configurations (NHBs) between adjacent molecules is of particular importance. A molecule may switch hydrogen-bonding p...