Pinacolone-Alcohol Gas-Phase Solvation Balances as Experimental Dispersion Benchmarks

Abstract

The influence of distant London dispersion forces on the docking preference of alcohols of different size between the two lone electron pairs of the carbonyl group in pinacolone was explored by infrared spectroscopy of the OH stretching fundamental in supersonic jet expansions of 1:1 solvate complexes. Experimentally, no pronounced tendency of the alcohol to switch from the methyl to the bulkier tert-butyl side with increasing size was found. In all cases, methyl docking dominates by at least a factor of two, whereas DFT-optimized structures suggest a very close balance for the larger alcohols, once corrected by CCSD(T) relative electronic energies. Together with inconsistencies when switching from a C4 to a C5 alcohol, this points at deficiencies of the investigated B3LYP and in particular TPSS functionals even after dispersion correction, which cannot be blamed on zero point energy effects. The search for density functionals which describe the harmonic frequency shift, the structural change and the energy difference between the docking isomers of larger alcohols to unsymmetric ketones in a satisfactory way is open.

Sniffing out camphor: the fine balance between hydrogen bonding and London dispersion in the chirality recognition with α-fenchol

“…This often energetically subtle isomerism for complexation can be used as an experimental benchmark for the predicted energy difference of electronic structure methods and can be tuned by modification of the donor or the acceptor molecule. [15][16][17] Here, we will also explore whether the preference might be influenced by simple mirroring of either interaction partner. Unlike chemical modifications, this does not change the intrinsic hydrogen bond acceptor or donor quality of the docking sites, therefore exposing geometric consequences from secondary interactions.…”

The Structures of ZnCl2-Ethanol Mixtures, a Spectroscopic and Quantum Chemical Calculation Study

“…The H-bonded networks in alcohols are readily susceptible to disruption and reformation by chemical perturbations [ 9 , 10 , 11 ]. Structural properties of alcohols in pure state or mixed with cosolvents and their relationship with H-bonds have been the subject of numerous experimental and computational studies [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. When it comes to electrolytes, their solvation in alcohols and aqueous alcohol solutions are of great significance in many industrial and natural processes [ 22 , 23 , 24 ].…”

Halogens in Acetophenones Direct the Hydrogen Bond Docking Preference of Phenol via Stacking Interactions

“…A hydrogen bond donor docks onto a divalent hydrogen bond acceptor and its docking preference between the two binding sites reflects not only the local bonding situation but also the interaction between more distant parts of the two molecules, which may come close to each other. Ketones as acceptors offer an important advantage [ 10 , 11 , 12 ]. They have two locally almost equivalent docking sites, the two lone electron pairs at the carbonyl oxygen, between which the donor molecule can switch easily.…”