Heats, equilibrium constants, and free energies of formation of the acetylene hydrocarbons through the pentynes, to 1,500-degrees K

Abstract

Values are presented for the following thermodynamic properties for acetylene, propyne (methylacetylene), I-butyne (ethylacetylene), 2-butyne (dimethylacetylene), 1-pentyne (n-propylacetylene), 2-pentyne (methylethylacetylene), and 3-methyl-l-butyne (isopropylacetylene), in the gaseous state, to 1, 500° K: The heat-content function, (HO-HOo)/T; the free-energy function, (F°-HOo) / T; the entropy, So; the heat content, HO-Hoo; the heat capacity, Cpo; the heat of format ion from the elements, AHjO; the free energy of formation from the elements, AFjO; and the logarithm of the equilibrium constant of formation from the elements, 10glO Kf. 1<. Equilibrium constants and concentrations of components are given in tabular and graphical form for the isomerization of the two butynes and of the three pentynes as a function of temperature to 1,500° K. Equilibrium constants are also given in tabular and graphical form for the dehydrogenation of ethane to ethylene to acetylene, of propane to propylene to propyne, of n-butane to I-butene to 1-butyne, and of n-pentane to 1-pentene to I-pentyne.

Heats, equilibrium constants, and free energies of formation of the monoolefin hydrocarbons

“…This plot may be compared with corresponding plots for the normal paraffins and the l-alkynes [4,5]. …”

“…(b) PENTENES AND HEXENES As no appropriate calorimetric data nor complete spectroscopic data for the pentenes were available, an approximate method of calculation was used for these molecules, similar to the method used for the pentynes [4]. This method involves the addition to the values for I-butene (modified as described below) of contributions arising from appropriate structural increments determined from the lower members of the paraffin and mono olefin series, with cognizance being taken, where necessary, of differences in the symmetry numbers and in the potential barriers restricting internal rotation.…”

“…V= (1/2)(I-sin 3ct»2400 cal/mole; 00<ct><2400 =00 cal/mole; 240° <ct>< 360° V=(1/2)(I-sin 3ct»2400 cal/mole; 00<ct><1200 (2) =2400 cal/mole; 120 0 < ct ><3600 (3) Type (d): V=(1/2)(I-sin 3ct»2400 cal/mole; OO<ct>< 3600 (4) A potential barrier of type (a) was used in the case of I-butene [1]. The equations of tables 1 and 2 for the pentene and hexene isomers in which the skeletal rotation adjacent to the ethylenic group is essentially the same as in I-butene do not mention potential barrier type (a) explicitly, as the effect of this hindering potential is included in the functions of I-butene.…”

“…:J.FoIT given in tables 30 and 31 for the isomerization of the butenes, pentenes, and hexenes. These plots may be compared with corresponding plots for the butanes, pentanes, hexanes, heptanes, octanes, butynes, and pentynes [4,5,6). From these charts, one may see at a glance, for any temperature in the given r ange and within the limits of uncertainty of the calculations, which of the isomers is thermodynamically most stable (lowest value of I1FOIT) and which is the least stable (highest value of I1Fo IT).…”

Heats of formation and combustion of 1,3-butadiene and styrene

“…Combination of eq 1c with the heat of formation of water from its elements [4,24] and with the h eat of combustion of n-butane [3,12] yields the following values for the heats of combustion of gaseous and liquid 1,3-butadiene, with all the reactants and products in their standa, rd reference states unless otherwise indicated:…”