| Abstract
| - A new approach for calculating bond dissociation energies(BDEs) from ES-MS/MS measurements has been developed. The new method features a “derived effectivereaction path length” that has been applied to measureBDEs of alkali metal (Li+) adducts and halide (Cl-)adducts of monoacylglycerol, 1,2-diacylglycerol, and 1,3-diacylglycerol lipids. Also studied were lithium-bounddimers of monoacylglycerols, 1,2-diacylglycerols, and 1,3-diacylglycerols. BDEs for the adducts and dimers of thelipids were derived from collision-induced dissociationexperiments using a triple quadrupole mass spectrometerwith electrospray as the ionization source. Mass spectraldata were used to empirically derive a single-exponentialgrowth equation that relates product cross section tocollision energy. From these single-exponential equations,a general second-order polynomial was derived using amultivariate growth curve model that enables predictionof BDEs of unknown complexes. Mass spectral resultswere compared to computer-generated bond dissociationenergies using Becke-style three-parameter density functional theory (B3LYP, employing the Lee−Yang−Parrcorrelation functional), with excellent agreement betweenexperimental and theoretical energy values. The newlydeveloped method is general in nature and can be usedfor the measurement of metal or halide ionic adduct bonddissociation energies and for the measurement of bondenergies of noncovalent interactions such as dimer dissociation energies. The validity of the method has beenrigorously established using a triple quadrupole, but itmay also be applied to other mass spectrometers thatallow user control of the collision cell potential.
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