The Heat Capacity of Gaseous Cyclopentane, Cyclohexane and Methylcyclohexane

Spitzer, Ralph; Pitzer, Kenneth S.

doi:10.1021/ja01216a032

Cited by 31 publications

(12 citation statements)

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“…The concept of pseudorotation, the "mutation" of a vibrational dof into a rotational dof, was introduced by Kilpatrick et al 47 to explain abnormal entropy and heat capacity values 105,106 observed for gaseous cyclopentane. Pitzer and coworkers argued that one of the two lowest-frequency degenerate (assuming D 5h point-group symmetry for the structure) ring-puckering modes of cyclopentane mutates and shows the properties of a rotation (basically no hindering potential).…”

Section: Pseudorotationmentioning

confidence: 99%

Quasistructural molecules

Császár

Fábri

Sarka

2019

WIREs Comput Mol Sci

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Section: Pseudorotationmentioning

confidence: 99%

Quasistructural molecules

Császár

Fábri

Sarka

2019

WIREs Comput Mol Sci

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“…The stated accuracy of the experimental data is 0.3-0.5. 62 The estimated uncertainty of the calculated values of C p is 0.54 and of differences between experimental and calculated values is 0.73 (Table 2a). Root mean square differences between calculated and experimental C p values lie within this standard deviation except for the C p values derived from the Beckett et al frequencies and their estimate of 5.6 kcal mol -1 for the energy difference of the twist boat and chair conformations…”

Section: Resultsmentioning

confidence: 97%

“…With the mPW1P95 functional, they report S(rrho) 62 16 i MP2/ 6-31G(d,p) geometry and frequencies SF 0.95/0.923. j Omitting nonexperimental values for Cp at 1000 K. k C(vib) at lowest two 6-31G(d,p) frequencies with SF 0.90. l Calculated from I(red) 4.49 × 10 -40 g cm 2 and V 3.28 kcal mol -1 (from MP2/6-311+G(2df,2p)//6-31G(d,p) energies).…”

Section: Resultsmentioning

confidence: 99%

Calculation of Entropy and Heat Capacity of Organic Compounds in the Gas Phase. Evaluation of a Consistent Method without Adjustable Parameters. Applications to Hydrocarbons

DeTar

2007

J. Phys. Chem. A

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The purpose of this study has been to determine how well a consistent ab initio thermostatistical method reproduces experimental values of heat capacity and entropy. The method has been applied to calculation of heat capacity and entropy of a representative set of hydrocarbons that includes compounds consisting of multiple conformers. All Cp and S values are for the gaseous state at 1 atm; units are cal K-1 mol-1. A detailed sensitivity (error) analysis has been performed to determine the root mean square (rms) values of errors expected of the calculated values: these are 0.27 cal for Cp and 0.36 cal for entropy. In comparing calculated values with experimental values, it is necessary to consider also the uncertainties of the experimental data. When these are included, the expected rms values of Cp(experimental) - Cp(calculated) values at 298.15 K range from 0.21 to 0.73. For S(experimental) - S(calculated), they range from 0.36 to 0.72. Calculations with frequencies derived with the 6-31G(d,p) basis set and scaled by 0.91 yielded rms values for Cp(experimental) - Cp(calculated) of individual compounds from 0.14 to 0.84 cal and rms values for S(experimental) - S(calculated) of individual compounds from 0.07 to 1.11 cal. Calculated Cp values for 7 out of 16 compounds agree with experimental values within the rms uncertainty estimated for the compound, and 11 fall within twice that estimate. For entropy, the calculated values for 13 of 18 compounds agree with the very limited available experimental data within the rms estimated uncertainty for the compound, and 16 of 18 fall within twice the uncertainty.

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“…If the residual thermodynamic functions of the members of an homologous series (at a specified temperature) correlate with the number, n, of spinal atoms according to [cf. eqn (9)] then the principle of congruence comprehends the statements l1 predicted HL = HL(x) for other binary n-alkane systems42 which agree less well with the experimental values than is the case when D is put equal to zero in eqn (25) and C is calculated from the x = 0.5 value of H L for the system n-hexane+n-…”

Section: T H E Principle Of Congruencementioning

confidence: 93%

Residual functions of the n-alkane liquids. Part 1.—Corresponding states and congruence

Cruickshank¹,

Drew²,

Mercer³

1975

J. Chem. Soc., Faraday Trans. 2

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The liquid-phase ( p e = 1 bar) residual Helmholtz free energy and enthalpy for the n-alkanes C6 to Cl0, with benzene and cyclohexane, and the residual Gibbs free energy for the n-alkanes C G to C I ~, are presented as polynomials in (T-273.15 K), valid up to the normal boiling point. The polynomials for the individual n-alkanes are mutually consistent. At any particular temperature, the standard deviation of each property, plotted against number of carbon atoms (for the n-alkane series) is much smaller than the estimated total uncertainty on individual values. The polynomials, together with those for standard liquid density, are used to show that neither the original two-parameter version of the principle of corresponding states, nor Patterson's generalisation of the version appropriate to the Orwell and Flory equation of state, is applicable to these hydrocarbons. We test also the principle of congruence for binary n-alkane mixtures, using experimental data for n-hexanef n-hexadecane ; the principle appears to be valid only as an empirical correlation.

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The Heat Capacity of Gaseous Cyclopentane, Cyclohexane and Methylcyclohexane

Cited by 31 publications

References 0 publications

Quasistructural molecules

Quasistructural molecules

Calculation of Entropy and Heat Capacity of Organic Compounds in the Gas Phase. Evaluation of a Consistent Method without Adjustable Parameters. Applications to Hydrocarbons

Residual functions of the n-alkane liquids. Part 1.—Corresponding states and congruence

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