C−H⋅⋅⋅O Hydrogen‐Bond‐Assisted Carboxylate⋅⋅⋅Carboxylate Interactions in a Prevented Decarboxylation of N ‐Acetate Isonicotinamide Betaine

Two acetic acid functionalized isonicotinamide (or 4‐carbamoyl‐1‐(carboxymethyl) pyridin‐1‐ium) salts with Br − and BPh 4 − anions have been prepared. The hydrophilic Br − and hydrophobic BPh 4 − anions result in two salts having different solubilities in water and acetone. Further recrystallizations of Br − and BPh 4 − salts from protic H 2 O/THF and aprotic acetone/ether solvents gave single crystals of a non‐decarboxylated zwitterion (a isonicotiamide betaine) and a decarboxylated isonicotiamides salt at room temperature respectively. A carboxylate−carboxylate dimer motif was observed in the zwitterion crystal structure. Theoretical calculations by using the PBE1PBE method at the cc‐pVDZ level indicate the carboxylate−carboxylate dimer motif was stabilized by the C−H⋅⋅⋅O hydrogen bonding assisted carbonyl⋅⋅⋅carbonyl interaction.