Conformation and the unique H-Bond of 2-(N,N-dimethylamino) benzoic acid in gas phase

Only a few examples on strong neutral hydrogen bonds are known in the chemical literature. this computational organic chemistry study illustrates that the most stable conformer of the title amino acid in gas phase is (i). the conformational analysis of (i) around the o1-c1 bond leads to destabilizing the structure due to breaking the n h1-o1 hydrogen bond. however,this could not be used to estimate the hydrogen bond strength due to an unexpected interfering destabilizing factor that could not be quantified. therefore,the hydrogen bond strength was estimated using a simulation model and the second order perturbation analysis. the b3lyp and the mp2 calculations predict the hydrogen bond in the gas phase to be stronger than 10 kcal/mol,which allows classifying it as a strong neutral hydrogen bond. to the best of our knowledge,this is the strongest neutral hbond encountered that it is not a resonance assisted h-bond (rahb). from a fundamental point of view,this example is a new addition to the hydrogen bond theory.