Saturated Vapor Pressure and Sublimation Enthalpy of l-serine and l-cysteine

Abstract

The crystal–vapor equilibrium for the standard amino acids l-serine and l-cysteine was studied by Knudsen effusion mass spectrometry in the temperature ranges of 387–442 and 361–429 K, respectively. At these relatively low temperatures, the surface degradation of the samples was shown to be minor. The vapor pressure obtained by the Knudsen effusion method was used to calibrate the mass spectrometer. The temperature dependence of the vapor pressure in the investigated temperature range is described by a linear equation ln­(p/Pa) = −(18.227 ± 289)/T + (39.828 ± 0.593) for l-serine and ln­(p/Pa) = −(16.658 ± 270)/T + (38.295 ± 0.806) for l-cysteine. The set of thermodynamic functions for l-serine and l-cysteine in the ideal gas state was developed. The sublimation enthalpy was obtained by the methods of the second and third laws of thermodynamics. The values Δsub H°(298.15 K) recommended from the analysis of all available data are 151.4 ± 2.3 and 142.5 ± 1.9 kJ mol–1 for l-serine and l-cysteine, respectively.

Saturated Vapor Pressure and Thermochemical Properties of l- and dl-Threonine

“…Instrument 1 , which has been employed in our previous works − and is described in detail and schematically represented in ref , was used to investigate the molecular composition of the vapor over l - and dl -threonine under electron ionization mode. A cylindrical single-section molybdenum effusion cell with the dimensions of 20 × 10 mm (internal height × diameter) and an effusion hole diameter of 0.5 mm (the ratio of evaporation and effusion areas is about 400; Cell 1) was used.…”

“…In our recent studies, − conducted using Knudsen effusion mass spectrometry (KEMS), the thermodynamic parameters of sublimation of L -tryptophan, l - and dl -methionine, l -serine, and l -cysteine were investigated, demonstrating the capabilities of KEMS in studying this class of compounds. The present work continues these investigations and focuses on l - and dl -threonine (2-amino-3-hydroxybutanoic acid; Figure ).…”

Effect of L-Cysteine on Micro-Galvanic Corrosion of ADC12 Aluminum Alloy in a Low-Conductivity Coolant for Electric Vehicles

“…In this regard, L-cysteine is a promising candidate to replace inorganic inhibitors because it is possible to inhibit corrosion, reduce electrical conductivity, and high melting temperature of 240 °C. 14 Some studies using L-cysteine as an additive have been reported. [15][16][17][18] L-cysteine exhibits corrosion inhibition even in severe corrosion environments such as 4 M NaOH solution.…”