Thermochemistry of Solution, Solvation, and Hydrogen Bonding of Cyclic Amides in Proton Acceptor and Donor Solvents. Amide Cycle Size Effect

Abstract

In the present work, the thermochemistry of solution, solvation, and hydrogen bonding of cyclic amides in proton acceptor (B) and proton donor (RXH) solvents were studied. The infinite dilution solution enthalpies of δ-valerolactam, N-methylvalerolactam, ε-caprolactam, and N-methylcaprolactam were measured at 298.15 K. The solvation enthalpies of cyclic amides were calculated based on the measured solution enthalpies and sublimation/vaporization enthalpies from literature. The enthalpies of hydrogen bonding between cyclic amides and proton acceptor and donor solvents were then calculated as a difference between the total solvation enthalpy and the non-specific contribution. The latter was estimated via two different approaches in proton donor and proton accepting solvents. The effect of the cycle size on the strength of hydrogen bonding of the cyclic amides in solution is discussed.

Enthalpies of Adduct Formation between Boron Trifluoride and Selected Organic Bases in Solution: Toward an Accurate Theoretical Entry to Lewis Basicity

“…The calculated values were almost always too high as compared to the experimental ones. A part of this discrepancy was attributed to a specific solvent effect of DCM, which is known to be a weak hydrogen bond donor (HBD) [50][51][52][53][54]. It may be considered that the interactions of DCM with the bases and BF 3 adducts were primarily dipole/dipole, but the structure of the interacting species (Figure 2) indicates an enhancement by directional hydrogen bonding, through the appropriate orientation of the DCM molecule.…”

Enthalpies of Adduct Formation between Boron Trifluoride and Selected Organic Bases in Solution: Toward an Accurate Theoretical Entry to Lewis Basicity

“…The calculated values are almost always too high as compared to the experimental ones. A part of this discrepancy was attributed to a specific solvent effect of DCM, which is known to be a weak hydrogen bond donor (HBD) [50][51][52][53][54]. It may be considered that the interactions of DCM with the bases and BF3 adducts are primarily dipole/dipole, but the structure of the interacting species (Figure 2) indicates an enhancement by directional hydrogen bonding, through the appropriate orientation of the DCM molecule.…”

The Solvation Effect of C=O Group of Cyclic Anhydrides in Solution

“…In this case, studies on associated solvents, including water, are of particular interest. Earlier, our group actively studied the intermolecular interactions of structural fragments of dipeptides and proteins (linear and cyclic amides) [ 12 , 13 , 14 , 15 , 16 ]. The effect of the number of active proton donor centers of linear amides on their proton donor properties in solution was shown [ 12 ].…”

“…The case when amides are solvent agents was considered, and the formation of hydrogen bonds of proton acceptors in amides was evaluated. Cooperativity and reorganization effects between amides and organic molecules in multi-particle complexes were discussed [ 14 , 15 ]. The realization of the interaction of protein structural fragments through N-H∙∙∙O=C hydrogen bonds was of particular interest, since it is these bonds that determine the stability of proteins [ 17 , 18 , 19 ].…”