Spectroscopic and dynamic NMR study, X-ray crystallography and DFT calculations of two phosphoramidates: (C4H3O2)P(O)(Cl)C6H14N and (C4H3O2)P(O)(C6H11NH)2

Synthesis and exploration of configurational dynamics in equilibratingE/Z2-aryliminothiazolidin-4-ones using NMR and estimation of thermodynamic parameters

“…The first-order rate constant k c was calculated for all the thiazolidin-4-one derivatives at coalescence temperature T c by employing the Gutowsky–Holm equation (eqn 4): 10,31–33 …”

“…This process also provides the rates of internal rotation and corresponding rotational barrier for several chemical systems such as amides, 6,7 [n]cumulenes, 8 metal-coordinated olefins, 2 twisted CQC bonds 9 and phosphoramidates. 10 Analyzing the dynamic equilibrium using VT DNMR helps in distinguishing coalescence temperature and in exploring the rotational energy barrier between two conformations using the Eyring equation. The correct interpretation of the spectrum is not possible when the signals approaching coalescence at room temperature give rise to broad and featureless lumps.…”

“…3) where [DG EZ ] ‡ is the free energy of activation for E to Z conversion; [DG ZE ] ‡ is the free energy of activation for Z to E conversion; X is calculated from [(X 2 -2)/3] 3/2 .1/X = DP; T c is the coalescence temperature; DP = P Z -P E (P Z 4 P E ) and P Z + P E = 1; P Z and P E stand for the populations of both conformers and Dn is the chemical shift difference (in Hz) between specific duplicated signals without exchange.The first-order rate constant k c was calculated for all the thiazolidin-4-one derivatives at coalescence temperature T c by employing the Gutowsky-Holm equation (eqn 4):10,[31][32][33] …”