✍ Scribed by Rudolf Hopmann
No coin nor oath required. For personal study only.
N‐Acetyl‐proline‐methylamide (APMA) was synthesized by the mixed anhydride method and investigated by IR. spectroscopy and chemical relaxation measurements. The temperature‐induced variation of the IR. absorption bands of the internally hydrogen bonded (b) and of the extended, unbonded (e) species at 3330 and 3450 cm^−1^ respectively, were used to evaluate the molar absorptivities, a(b) = 280 and a(e) = 50 l/mol · cm, the equilibrium constant K = 0.70, and the molar enthalpy of reaction Δ__H__ = − 2280 ± 60 cal/mol. The entropy was estimated to be in the range − 8 to − 9 e.u. The reaction rates of this conformational transition were measured by the chemical dipole field effect. The relaxation time of the rate process is τ = 2.7 · 10^−9^s, the rate constant for the formation of the hydrogen bond k(b) is 2.2 · 10^8^ s^−1^, and that for the unfolding accompanied by the breakage of the amide hydrogen bond k(e) is 1.5 · 10^8^s^−1^.
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