The Thermodynamic Properties and Molecular Structure of Cyclohexane, Methylcyclohexane, Ethylcyclohexane and the Seven Dimethylcyclohexanes<sup>1</sup>

Beckett, C.W.; Pitzer, Kenneth S.; Spitzer, Ralph

doi:10.1021/ja01202a070

Cited by 265 publications

(81 citation statements)

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“…Then t h e law of the most probable distribution is, Flory [5, p . 319] (2) with (3) as the equation d etermining p. Substituting from (2) and (3) into (1), approximating to the factorials by means of Stirling's theorem, we find , after performing the summations called for by (1),…”

Section: Differing Molecular Weightsmentioning

confidence: 99%

“…Th ese fi gures have been shown to be nearly righ t by studies of a large number 0 r elated hydrocarbons; see, for example, Pitzer [20], [21]; Pitzer and Kilpatri ck [23]; Beckett, Pitz er, and Spitzer [1]; Pitzer and B eck ett [22]; Person and Pimentel [19].…”

Section: 1 a Priori Expectationsmentioning

confidence: 99%

“…It is known that crystallization of a polymer is never complete, and some polymers cannot crystallize at all. Moreover, polymer undergo a "glass-like" transition at 1 Figures in brackets indicate the literature references at the end of this paper.…”

Section: Introductionmentioning

confidence: 99%

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Residual entropy of linear polymers

Temperley¹

1956

J. RES. NATL. BUR. STAN.

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The question whether it is possibJe to assign a finite entropy to a polym er, bearing in mind the fact that it may not be a well-defined substance in thermodynamic equilibrium , is considered. It is shown that the entropy of chain configuration s is the only contribu t ion t hat will be important at low temperatures. Existing knowl edge of t he t hermodynamics of hydrocarbons enables one to a rri ve at a generalization of the well-known " flexibJ e chain " model of a polymer molec ule. The new model is in good accord with experim en tal facts on the specific heat of polym ers, and enables a finite entropy to be defined and to be reasonably accurately calculated. These findings are then compared with certain experimental r es ul ts throwing light on t he length of the "effective segmeut" of polym er chains of va r, ious types, this quantity being defined in t he text. The experimental facts come from studIes of polym er solu tions, solid polymers, solid and liquid paraffin s, and related COlnpounds, and arc remarkably consistent with the theoretical expectations. A few apparent inconsistencies an d a few instances of alternative possible interpretations for the sam e facts are noted .

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Section: Differing Molecular Weightsmentioning

confidence: 99%

Section: 1 a Priori Expectationsmentioning

confidence: 99%

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Residual entropy of linear polymers

Temperley¹

1956

J. RES. NATL. BUR. STAN.

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“…(2) In eq 2, the term [steric factor] is the contribution of the equatorial-polar tautomerism of methylcyclohexane to its ' th ermodynamic functions . The term [methyl] is therefore the difference between the functions of methyleyclohexane and eyclohexane, without the inclusion of the effects of tautomerism and of symmetry number.…”

Section: Methods and Data Used In The Calculationsmentioning

confidence: 99%

Heats, equilibrium constants, and free energies of formation of the alkylcyclopentanes and alkylcyclohexanes

Kilpatrick¹,

Werner²,

Beckett³

et al. 1947

J. RES. NATL. BUR. STAN.

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For cyc lopentane, cyclohexane, the seven dimethylcyclohexanes, and the normal alkylcyclopen tancs a nd a lkylcyclohexanes, valu es a re presen ted for t he folJo"'ing thermodynamic properties to 1,000° or 1,500 0 K: The heat of formation from the clements; t he fre e energy of formati on fro m the elem ents ; and t he logari thm of t he eq uilib ri um constant of forma tion from the elements. Fo r cyclopen tane, cyclohexane, and t he normal a lk ylcyclopentan es and a lk y lcyc lohexanes, valu es are a lso given to 1,500 0 K, for the followin g p ropert ies: The heat-content function; the free-energy function; the en tropy; the heat content; and the heat capacity.Equilibrium co nstants and concen tration s a re giv en i n tab ul a r a nd graphical form for som e r eaction s of isomeri zation, hydrogena t ion, and cycli zatiol1 . L IntroductionAs a part of the work of t he American Petroleum Institute R esearch Proj ect 44 at t h e National Bureau of Standards and th e Univcrsity of Oalifornia, values have b een calculated for the h eatcontent function, free-energy {unction , entropy, heat content and heat capacity of t he normal alkylcyclopcn tanes and the normal alkylcyclohexanes above ethylcyclohexane, in t he gaseous state to 1,500° K . These data, together with previously published data on cyclopentane, cycloh exane, methylcyclohexanc, and ethylcyclohexane, have been combined with values of the h eats of formation at 25° 0 to calculate values of the h eats, free en ergies, and equilibrium constants of formation of 17 alkylcyclopentanes and 24 alkylcyclohexau.es . The free energies and equilibrium C011- II. Fundamental ConstantsThe uni t of en ergy, atomic weights, and values of the fundamental constants used in t his l'('port are th e sam e as t hose previously used [5,13] For cyclopentane, cycloh exane, m ethylcycloh exan e, ethylcyclohexane, and t he seven climethylcycloh exanes, th e values wer e taken fro m r eferences [I, 2] .For ll1et uylcyelopen tane, th e th ermodyn amic functions were calculated by means of the following r elat.i on :[methylcyclopentane] = [cyclopentane] + [methyl] + [restricted rotation of rin g puckerin g] + (R In] 0).(1)The terms written in brackets r epresent a given t h ermodynamic funct,ion of t he indicated sub-

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“…23 However, the vibrational spectroscopic and thermodynamic data were interpreted in terms of the predominant existence of the chair conformer. 36 Moreover, temperaturedependent NMR spectra are only devoted to the determination of the kinetic parameters for the chair ↔ chair interconversion. [37][38][39][40] There are two kinds of the diagonal C ·C distances in a cyclohexane molecule.…”

Section: Liquid Cyclohexanementioning

confidence: 99%

Analysis of Liquid Structure without Construction of Any Structure Models by the X-Ray Scattering Method

2007

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Since a study on liquid paraffin by Debye and Scherrer, 1 a large number of structural studies on various liquids have been conducted by the X-ray scattering method. The structure of liquid water in various conditions has been examined by many investigators.2,3 Structural information on organic liquids has also been accumulated. [4][5][6][7] Due to large fluctuations caused by molecular motions in long distant regions, analyses of a liquid structure by the X-ray scattering method require one to make up a local structure model, i.e., an aggregate consisting of several liquid molecules, which best reproduces the X-ray scattering data.The simplest approach to deduce a structure model of a liquid will refer to a partial structure present in its crystal when the crystal structure has been determined. The interstitial model of liquid water by Narten 8 is the most famous example. Determinations of the local structure of organic liquids such as benzene, formamide, dimethyl sulfoxide, and N-methylacetamide at ambient temperature (their melting points are 5. 493, 2.55, 18.55, and 30.55˚C, respectively) are successful examples based on the partial structure in the crystal. [9][10][11][12] In order to obtain further information on the longer range intermolecular interactions of molecular liquids, Iijima and Nishikawa proposed the reciprocal space expansion in the analysis of X-ray scattering data. 13,14 However, these procedures do not apply if the temperature of a liquid is far from its melting point because of large differences of densities between solids and liquids. The intermolecular distances among molecules in a liquid are quite different from those in a solid phase.Another approach to construct a liquid structure is one that uses physicochemical properties of liquid molecules. When a liquid is protic and has a hydrogen-bonding ability, a two-or three-dimensional hydrogen-bonded network should be taken into account. For an aprotic polar liquid molecule, a negatively charged atom of a molecule approaches a positively charged atom of another molecule according to the charge distributions of the molecules. Also, molecules are piled up interacting with their dipole moments in an antiparallel way. Considering these patterns, one searches for molecular arrangements which reproduce X-ray scattering data well by a trial-and-error method. A good example is the structural determination of liquid acetonitrile. [15][16][17][18][19] However, analysis by this approach is a laborious task. Thus, a simple approach for determining a liquid structure without constructing any plausible structure models is necessary.Two methods have been used frequently for studying liquid structures without constructing any plausible models, i.e., the reverse Monte Carlo (RMC) 20 method and the empirical potential structure refinement (EPSR) 21 method. The RMC method is the computer simulation based on the Metropolis Monte Carlo procedure: a particle or a molecule moves so as to decrease the difference between the experimental scattering data and cal...

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The Thermodynamic Properties and Molecular Structure of Cyclohexane, Methylcyclohexane, Ethylcyclohexane and the Seven Dimethylcyclohexanes¹

Cited by 265 publications

References 0 publications

Residual entropy of linear polymers

Residual entropy of linear polymers

Heats, equilibrium constants, and free energies of formation of the alkylcyclopentanes and alkylcyclohexanes

Analysis of Liquid Structure without Construction of Any Structure Models by the X-Ray Scattering Method

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The Thermodynamic Properties and Molecular Structure of Cyclohexane, Methylcyclohexane, Ethylcyclohexane and the Seven Dimethylcyclohexanes1

Cited by 265 publications

References 0 publications

Residual entropy of linear polymers

Residual entropy of linear polymers

Heats, equilibrium constants, and free energies of formation of the alkylcyclopentanes and alkylcyclohexanes

Analysis of Liquid Structure without Construction of Any Structure Models by the X-Ray Scattering Method

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Product

Resources

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The Thermodynamic Properties and Molecular Structure of Cyclohexane, Methylcyclohexane, Ethylcyclohexane and the Seven Dimethylcyclohexanes¹