Stig Sunner

Enthalpies of vaporization of some 1-substituted n-alkanes

Abstract Enthalpies of vaporization at 298.15 K have been determined calorimetrically for some 1-substituted straight-chain alkanes. The results are: Compound ΔH v o /kJ mol −1 Compound ΔH v o /kJ mol −1 1-octene 40.27 ± 0.20 1-bromooctane 55.77 ± 0.25 1-decene 50.43 ± 0.20 1-bromododecane 74.77 ± 0.38 1-dodecene 60.78 ± 0.20 1-bromohexadecane 94.4 ± 1.5 1-hexadecene 80.25 ± 0.42 methyl pentanoate 43.10 ± 0.06 1-hexanol 61.85 ± 0.20 methyl hexanoate 48.04 ± 0.12 1-heptanol 66.81 ± 0.20 methyl heptanoate 51.62 ± 0.48 1-octanol 70.98 ± 0.42 methyl octanoate 56.41 ± 0.50 1-nonanol 76.86 ± 0.75 methyl nonanoate 61.99 ± 0.41 1-decanol 81.50 ± 0.75 methyl decanoate 66.75 ± 0.57 1-dodecanol 91.96 ± 0.59 methyl undecanoate 71.37 ± 0.30 1-tetradecanol 102.2 ± 2.3 methyl dodecanoate 77.17 ± 0.56 1-mercaptodecane 65.48 ± 0.54 methyl tridecanoate 82.68 ± 0.84 methyl tetradecanoate 86.98 ± 0.94 1-chloropropane 28.50 ± 0.21 methyl pentadecanoate 93.49 ± 0.94 1-chlorododecane 71.93 ± 0.32 1-chlorohexadecane 91.8 ± 1.1 An analysis of available data shows that the enthalpy of vaporization for members within seven homologous series, XC m H 2m + 1 , can be expressed as ΔH v o (X, m ) = A x + B x m .

A comparison of standard reactions for solution and combustion calorimetry II. Combustion-calorimeter measurements

Abstract The enthalpy of reaction of tris(hydroxymethyl)-aminomethane ( Tris ) with excess dilute hydrochloric acid has been compared with the enthalpy of reaction of sulfuric acid with excess sodium hydroxide at low and high concentrations. In the following paper, the enthalpy of the H2SO4+NaOH reaction at high concentration has been measured relative to the enthalpy of combustion of benzoic acid. Combination of the results permits deduction of the enthalpies of the H2SO4+dilute NaOH and Tris +HCl reactions, independent of the absolute accuracy of the electrical-heating calibrations of the solution calorimeter.

On the Interpretation of Ring Strain

The effect of pressure—volume energy, nuclear motions, and reference system on estimated strain energies of mono and polycyclic ring compounds is discussed. Strain energies calculated by common procedures are shown to contain contributions not usually taken into consideration in discussions on ring strain. The dependence of strain‐energy values on the choice of reference system is exemplified.

The energy of combustion of succinic acid

Abstract The energy of combustion of a thoroughly dried sample of succinic acid was measured by oxtgen-bomb combustion calorimetry, with the result: ΔU o o (298.15 K ) M = −(3020.86±0.54) cal th g −1 from six combustions. The results of 15 previous investigations on the energy of combustion of succinic acid were critically reviewed and recalculated to 298.15 K and standard state conditions. The weighted mean values for succinic acid are: ΔU o o M = −(3020.55±0.38) cal th g −1 ; ΔU o o = −(356.69 7 ±0.045) kcal th mol −1 ; ΔH o o = −(356.40 1 ±0.045) kcal th mol −1 ; ΔH t o = −(224.75±0.13) kcal th mol −1 . The optimum procedures for use of succinic acid as a test substance in combustion calorimetry are discussed.

Enthalpies of formation of mono- and diammonium succinates and of aqueous ammonia and ammonium ion☆

Abstract The energies of combustion of mono- and di-ammonium succinates were measured by rotating-bomb combustion calorimetry. Enthalpies of solution of the two salts and of succinic acid were obtained by solution calorimetry. The results were used with other data to evaluate enthalpies of formation as follows: State ΔH f o (298.15 K)/kcal th mol −1 Monoammonium succinate c −255.22±0.21 Diammonium succinate c −282.67±0.18 NH 4 + aq −31.820±0.045 NH 3 aq −13.395±0.045

A general-purpose reaction-solution rotating-bomb calorimeter for measurements up to about 400 K and 800 kPa

A reaction-solution rotating-bomb isoperibol calorimeter has been developed and tested. It consists of the calorimeter bomb with surrounding can, and accessories including a control box. These units together with an LKB 8710 control unit and a suitable thermostat constitute the calorimeter assembly Potassium chloride and tris , tris(hydroxymethyl)aminomethane, dissolution experiments were carried out between 298 and 390 K and between 298 and 360 K, respectively. The results have been compared with literature data.

Enthalpies of formation of some 1-chloroalkanes and the CH2-increment in the 1-chloroalkane series☆

Abstract Enthalpies of combustion at 298.15 K have been measured for some 1-chloroalkanes and enthalpies of formation derived for the compounds in the liquid and gaseous states. The results are (uncertainties given are twice the overall standard deviation of the mean): ΔH f o (l)/kJ mol −1 ΔH f o (g)/kJ mol −1 1-Chlorobutane −188.15 ± 1.15 −154.63 ± 1.15 1-Chloropentane −213.44 ± 1.25 −175.20 ± 1.25 1-Chlorooctane −291.30 ± 1.87 −238.88 ± 1.87 1-Chlorododecane −392.31 ± 2.40 −321.98 ± 2.46 1-Chlorooctadecane −544.20 ± 2.82 −446.04 ± 3.06 The enthalpies of formation in the gaseous state of these compounds combined with those of chloroethane,(1) and 1-chloropropane,(1) give a CH2-increment in the series of −(20.952 ± 0.146) kJ mol−1, where the given uncertainty limit represents twice the overall standard deviation.

Evaluation of excess enthalpies from flow-calorimetric measurements of enthalpies of dilution using local approximation by polynomials

Abstract A method is described for the evaluation of excess enthalpies of binary mixtures from results of flow-calorimetric measurements of enthalpies of dilution and mixing of mixtures of the components. The power Q generated when two mixtures of mole fractions x A and and x B are mixed can be expressed as: Q = ( n A + n B )H E (x C ) − n A H E (x A ) − n B H E (x B ) where n denotes molar flow rate of the respective solution and H E the molar excess enthalpy at the indicated mole fraction. From a series of measurements covering the whole composition range, sets of equations containing H E ( x ) as unknowns are obtained. One assumes that values of H E ( x ) can be interpolated from values of H E ( z ) at a fixed set of mole fractions “z’ using a linear interpolation formula H E ( x ) = Σc 1 H E ( z 1 ). In each interpolation a fixed number of z -nodes closest to x are used. The coefficients c 1 are calculated as the coefficients in the Lagrangian interpolation formula and depend only on x and z 1 . The resulting overdetermined linear equation system which contains the values of H E ( z ) as unknowns is solved by a standard least-squares procedure. Intermediate values of H E are interpolated from the calculated set. The advantage of the method is that no analytical expression for H E as a function of composition is needed. The method has been tested on water + ethanol at 298.15 K. Values of H E derived in the present study agree well with directly determined values of H E reported in the literature. The approximation method presented is considered applicable generally for the evaluation of integral quantities from results of measurements of differential quantities.

Enthalpies of vaporization at 298.15 K for some 2-alkanones and methyl alkanoates☆

Abstract Enthalpies of vaporization ΔH va p at 298.15 K were determined for some methyl alkanoates and 2-alkanones. The following values of ΔH vap o /kJ mol −1 , were obtained: methyl ethanoate, (32.60 ± 0.06); methyl propanoate, (35.82 ± 0.09); methyl butanoate, (39.28 ± 0.22); 2-butanone, (34.51 ± 0.08); 2-heptanone, (47.24 ± 0.05); and 2-undecanone, (67.00 ± 0.41). For the compounds 2-tetradecanone and 2-pentadecanone, enthalpies of vaporization at 298.15 K were derived from experimental determinations of enthalpies of sublimation at 298.15 K, enthalpies of fusion, and heat capacities. The following results were obtained: for 2-tetradecanone, ΔH sub o = (130.92 ± 0.45) kJ mol −1 , ΔH fus o = (49.12 ± 0.36) kJ mol −1 at 306.7 K; for 2-pentadecanone, ΔH sub o = (139.26 ± 1.62 kJ mol −1 , ΔH fus o = (54.57 ± 0.33 kJ mol −1 at 312.2 K.

Enthalpies of combustion, vaporization, and formation of some alkanenitriles, and the CH2-increment in the alkanenitrile series

Abstract Energies of combustion and enthalpies of vaporization at 298.15 K were measured for some alkanenitriles and enthalpies of formation were derived for the compounds in the liquid and gaseous states. The results are: Δ H° f (1) kJ mol −1 Δ H° v kJ mol −1 Δ H° f kJ mol −1 Octanenitrile −107.4 ± 1.5 56.80 ± 0.27 −50.6 ± 1.5 Decanenitrile −158.4 ± 1.8 66.84 ± 0.37 −91.6 ± 1.8 Undecanenitrile −184.5 ± 2.0 71.14 ± 0.14 −113.4 ± 2.0 Dodecanenitrile - 76.12 ± 0.14 - Tetradecanenitrile −260.1 ± 2.6 85.29 ± 0.51 −174.8 ± 2.7 The uncertainties given represent twice the final overall standard deviations of the means. Least-squares analysis of the enthalpies of formation from the literature (1–3) and from the present study gives: ΔH° f { H(CHCN,g} kJ mol −1 = (95.20 ± 1.33) − (20.815 ± 0.203)m, (m ⩾ 3), where the uncertainties represent twice the calculated standard deviations. The CH 2 -increment is in good agreement with the generally accepted value. (4) The enthalpies of vaporization at 298.15 K of alkanenitriles can be represented by: Δ H° v {H(CH 2 ) m  CN } kJ mol −1 = 23.50 + 4.736m where V m is the molar volume. The mean and maximum deviations between calculated and experimental values are 0.19 and 0.41 kJ mol −1 , respectively