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

Ilnaz T Rakipov,Aydar A Akhmadiyarov,Artashes A Khachatrian,Timur A Mukhametzyanov,Boris N Solomonov,Artem A Petrov

doi:10.3390/molecules26051411

Ilnaz T Rakipov, Aydar A Akhmadiyarov + Show 4 more

Open Access

https://doi.org/10.3390/molecules26051411

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Journal: Molecules (Basel, Switzerland)	Publication Date: Mar 5, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Kazan Federal University

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.

Highlights

Cyclic amides and their derivatives demonstrate elastase inhibition [1], profound antihistaminic activity [2], and a hepatoprotective effect [3]; they are researched as components of anticancer drugs [4], electrolytes for batteries [5], and as ligands for catalytic reactions [6]
The solution enthalpies of N-methylbutyrolactam, δ-valerolactam, N-methylvalerolactam, ε-caprolactam, and N-methylcaprolactam were measured at standard conditions (298.15 ± 0.01 K, 0.1 MPa) using the semi-adiabatic solution calorimeter constructed in Kazan Federal University and TAM III (TA Instruments, New Castle, PA, USA) isothermal solution calorimeter
The proton donor and proton acceptor properties were studied in the range of the linear amides

Summary

Introduction

Cyclic amides (lactams) and their derivatives demonstrate elastase inhibition [1], profound antihistaminic activity [2], and a hepatoprotective effect [3]; they are researched as components of anticancer drugs [4], electrolytes for batteries [5], and as ligands for catalytic reactions [6]. The intermolecular interactions of cyclic amides were studied by different experimental and theoretical methods [7,8,9,10,11,12,13,14]. The intermolecular interactions of linear and cyclic amides in the solutions were studied following the approach based on solvation thermochemistry [15,16,17]. The thermochemistry of hydrogen bonding of linear and cyclic amides with proton acceptor solvents was studied in [16]. The intermolecular interactions of proton acceptors in the linear and cyclic amides media were researched [17]. The solution enthalpies of δ-valerolactam, N-methylvalerolactam and ε-caprolactam, N-methylcaprolactam in proton acceptor and proton donor solvents were measured at 298.15 K. Detailed information about studied samples, their purity, and water content are presented in Supplementary Materials (Table S1)

Solution Calorimetry

Conclusions