Thermal Data. I. The Heat Capacities, Entropies and Free Energies of Seven Organic Compounds Containing Nitrogen

Abstract

We have recently begun in this Laboratory a systematic study of some of the thermal properties of physiologically important organic compounds. These investigations are to include studies of low temperature heat capacities and heats of combustion. The data thus obtained may be utilized to calculate the entropies and free energies of the compounds by means of the third law of thermodynamics and the fundamental thermodynamic equation AF = AH -T AS. In this paper are presented the low temperature specific heat data for the following seven compounds: ¿-alanine, /-asparagine, /-asparagine hydrate, /-aspartic acid, ¿-glutamic acid, creatine and creatinine. We have also included the corresponding entropies and free energies calculated from these data by means of the third law of thermodynamics.Materials ¿-Alanine.-This material was placed at our disposal for this investigation by the Hoffmann-La Roche Laboratories, Nutley, New Jersey. It was subjected to several crystallizations from water by adding a large excess of alcohol. The resulting material gave theoretical values for total nitrogen. The specific rotation of the hydrochloride was, a2£ 10.1°./-Asparagine Hydrate.-Material obtained from Merck was subjected to a number of fractional crystallizations by rapidly cooling the hot aqueous solution to prevent racemization. The Kjeldahl analysis gave the theoretical results within the error of the method. A solution, having a volume of 25 cc. at 20°, containing 10% hydrochloric acid and 2.5236 g. of the monohydrate gave the rotation a2S 27.0 °./-Asparagine Hydrate.-The hydrated acid described above was dried in an oven at 100-110°to a constant weight. /-Aspartic Acid.-An Eastman product was recrystallized seven times. The sample gave the theoretical values for nitrogen and free amino groups. A solution containing in 25 cc. at 20°, 2.2903 g. of this acid, and 3 mole equivalents of hydrochloric acid gave a rotation a2£ 26.42°.¿-Glutamic Acid.-This material was prepared from Ajinomoto according to the method of Schmidt and Foster.1 The final product gave the theoretical values for nitrogen and free amino groups. A solution containing in 25 cc. at 20°, 1.269 g. of the acid and 0.2483 g. of hydrochloric acid gave the rotation a2£ 31.1.Creatine.-A Pfanstiehl product was subjected to several fractional crystallizations. The final product gave the theoretical values for nitrogen.Creatinine.-A very pure Pfanstiehl product was further purified by the methods of Edgar and Hinegardner.2 The resulting product gave the theoretical values for nitrogen.

A thermodynamic study of the hydrolysis of L-glutamine to (L-glutamate + ammonia) and of L-asparagine to (L -aspartate + ammonia)

“…A similar calculation (this will be referred to as thermochemical cycle "B") can be performed that leads to K m for reaction (6). Here, we have the following for Lasparagine · H 2 O(s): f H o m = −1086.6 kJ · mol −1 given by Pedley et al (23) based on the value of c H o m determined by Huffman et al; (29) S o m = 213.4 J · K −1 · mol −1 given by Domalski et al (25) based on the heat capacity measurements of Hutchens and Borsook; (30) and m(sat) = 0.19 mol · kg −1 given by Hutchens. (27) This leads to…”

Heat Capacities of l-Arginine, l-Aspartic Acid, l-Glutamic Acid, l-Glutamine, and l-Asparagine

“…Heat capacity of the Cu cup was subtracted from the total heat capacity using data recommended by Arblaster [16]. This technique was checked by measurement of compounds with reliable data obtained by adiabatic calorimetry (anthracene [17], l-asparagine [18], and glycine [19]) and uncertainty of results was found comparable to this reported previously [20] for samples encapsulated in Al DSC pans, i.e., the combined expanded uncertainty (0.95 level of confidence) of the heat capacity measurements is estimated to be…”

A box‐counting‐based algorithm for computing Shannon entropy in molecular dynamics simulations

“…Several points have to be considered about the experimental S data for amino acids before performing the comparison with our Sh*( E S ) values. (1) First of all, it has to be said that very few experimental studies were carried out on these compounds 28–39. Very close, but different, values observed in different tables or data basis are due to successive changes of units and/or rounding off.…”

“…Therefore, we have only taken into account the values presented in the original works. Thus, the set of available data reduces to: (a) only one value for Asn,28 Cys,29 Gln,30 Ile,31 Met,32 Phe,33 Ser,34 Trp,33 and Val;31 (b) two values for Asp,28, 30 Glu,28, 30 Gly,35, 36 Leu,31, 37 Pro,30, 38 and Tyr;33, 36 and (c) three values for Ala 28, 36, 39. (2) All the available experimental values of S were obtained from C P heat capacities measured along a certain interval of temperatures, [ T 1 − T 2 ].…”