Researchers from IQFR (J. Dávalos, A. Guerrero, J. Gonzalez, A. Chana) in collaboration of Prof. T. Baer (University of North Carolina-USA) have determined the acidity GA -in the gas phase- of the hydroxyl and carboxyl local groups of the hydroxycinnamic acids, applying the kinetic method (EKM) in a mass spectrometer with electrospray (ESI)-source. Hydroxycinnamic acids are natural compounds found in several biological sources mostly in the plant kingdom either as esters of organic acids or glycosides, bound to proteins or as free acids.

The most important contribution of this work has been to show that is possible to determine gas-phase acidities (GAs) or basicities (GBs) of different deprotonation or protonation sites of a same molecule, only by a careful control of the ESI-experimental conditions; since the measurement of GA or GB of monofunctional molecules not offer a new scientific challenge.

This work opens the implementation of new experimental methodologies (e.g. using ESI-MS) to extract and quantify reliable thermodynamic properties, such as GA or GB, of different local groups within a multifunctional molecule.

Reference: Gas phase acidity measurement of local acidic groups in multifunctional species: Controlling the binding sites in hydroxycinnamic acids, A. Guerrero, T. Baer, A. Chana, F.J. González, and J.Z. Dávalos, J. Amer. Chem. Soc. (2013) DOI:10.1021/ja400571r