Ultrasonic Relaxation and Axial—Equatorial Isomerization in Methylcyclohexane. II

Piercy, J. E.; Subrahmanyam, S. V.

doi:10.1063/1.1695875

Cited by 28 publications

(12 citation statements)

References 13 publications

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“…Nevertheless a similar situation occurs for another secondary process observed in ethylcyclohexane: the γ-process [2]. The existence of such relaxation slower than the α-relaxation was previously pointed out by means of acoustic attenuation measurements on ethylcyclohexane [ 44] and on methylcyclohexane [45] at ultrasonic frequencies in the kHz range. The comparison with mechanical measurements on other cyclohexane-derived materials suggested a chair-tochair conformational transition of the cyclohexane ring as the probable physical origin of the relaxation [1].…”

mentioning

confidence: 79%

On the features of the dielectric response of supercooled ethylcyclohexane

Mandanici

Huang

Cutroni

et al. 2008

Philosophical Magazine

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mentioning

confidence: 79%

On the features of the dielectric response of supercooled ethylcyclohexane

Mandanici

Huang

Cutroni

et al. 2008

Philosophical Magazine

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“…We also carried out density functional theory [5] 140 ± 105 0.4 ± 0.3 MW [6] 104 ± 10 0.30 ± 0.03 MW [7] 52 0.15 NMR (soln) [8] 74 0.21 NMR (liq) [9] 88 ± 5 0.25 ± 0.01 NMR (gas) [10] 67 0.19 MM [11] 109 ± 33 0.31 ± 0.09 Liq Kr [12] 33 0.09 MP2 [1] Chlorocyclohexane 150 0.43 NMR (soln) [8] 178 ± 52 0.51 ± 0.15 MW [13] 92 ± 11 0.26 ± 0.03 Raman [3] 226 ± 58 0.65 ± 0.17 ED [2] 133 0.38 MM2 [14] 140 0.40 IR [15] 150 0.43 MP2 [1] Bromocyclohexane 129 0.37 NMR (soln) [8] 252 ± 105 0.72 ± 0.30 MW [16] 176 ± 18 0.50 ± 0.05 ED [2] 164 0.47 MM2 [14] 213 ± 7 0.61 ± 0.02 IR [17] 202 0.58 MP2 [1] Methylcyclohexane 690 ± 21 1.97 ± 0.06 IR [17] 1014 ± 175 2.9 ± 0.5 U. Relax [18] 603 ± 20 1.74 ± 0.06 13 C-NMR [19] 615 ± 34 1.76 ± 0.10 13 C-NMR [20] 671…”

Section: Introductionmentioning

confidence: 98%

Conformational stability of chlorocyclohexane from temperature-dependent FT-IR spectra of xenon solutions, r 0 structural parameters, and vibrational assignment

et al. 2008

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Variable temperature (-55 to -105°C) studies of the infrared spectra (4000-400 cm -1 ) of chlorocyclohexane (c-C 6 H 11 Cl) dissolved in liquefied xenon have been carried out. The infrared spectra of the gas and solid have also been recorded from 4000-100 cm -1 . By analyzing six conformer pairs in the xenon solution, a standard enthalpy difference of 132 ± 13 cm -1 (1.58 ± 0.16 kJ/mol) was obtained with the equatorial conformer the more stable form. At ambient temperature, the abundance of the axial conformer is 34 ± 1%. The potential surface describing the conformational interchange has been determined and the Fourier coefficients were obtained. From MP2 ab initio calculations utilizing various basis sets with and without diffuse functions, the equatorial conformer is predicted to be more stable by 161 ± 18 cm -1 from the four largest basis set calculations, which is consistent with the experimental results. However, the average from the corresponding B3LYP density functional theory calculations is 274 ± 15 cm -1 which is certainly too large. By utilizing the previously reported microwave rotational constants for two isotopomers ( 35 Cl, 37 Cl) combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r 0 structural parameters have been obtained. The determined heavy atom distances for the most stable chairequatorial conformer in Å are: r 0 (C 1 -C 7 , 8 ) = 1.532(3); r 0 (C 7 , 8 -C 13 , 14 ) = 1.536(3); r 0 (C 4 -C 13 , 14 ) = 1.524(3); and r 0 (C 4 -Cl 6 ) = 1.802(5) and the angles in degrees: \C 1 C 7 , 8 C 13 , 14 = 111.3(5)8; \Cl 6 C 4 C 13 , 14 = 109.7(5)8 with the two dihedral angles \C 8 C 1 C 7 C 13 = 56.3(10)8 and \C 14 C 4 C 13 C 7 = 56.7(10)8. These parameters are in good agreement with those reported earlier from microwave and electron diffraction studies where the CC and CH distances were all assumed to be equal. A few of the previously reported vibrational assignments have been corrected. The results of these spectroscopic and theoretical studies are discussed and compared to the corresponding results for some similar molecules.

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“…At the time of revision of the manuscript, one of the referee has brought to our notice two very recent publications 27,28 along with some older publications which discuss the possibility of various intramolecular modes such as the one associated with chairchair transformation and side group relaxation in cyclohexyl derivatives. [29][30][31] Therefore, sub-T g process͑es͒ of these solutes with cyclohexylchloride in different glassy matrices have been determined, compared to that of ICNCH and CNCH.…”

Section: Introductionmentioning

confidence: 99%

Study of secondary relaxation in disordered plastic crystals of isocyanocyclohexane, cyanocyclohexane, and 1-cyanoadamantane

Singh

Murthy

2008

The Journal of Chemical Physics

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In the present communication, dielectric relaxation investigations on three interesting supercooled plastic crystalline substances, i.e., isocyanocyclohexane (ICNCH), cyanocyclohexane (CNCH), and 1-cyanoadamantane (CNADM) are reported. All of these have the main dipole moment situated in their side group- C[Triple Bond]N or- N[Triple Bond]C. Differential scanning calorimetry (DSC) was also employed as a supporting technique. Glassy crystal were easily formed in the first two samples by slowly cooling the plastic phase, but in CNADM it was formed by rapidly quenching the room temperature plastic phase. In addition to the so called alpha process that can reasonably be described by a Havriliak-Negami (HN) shape function, a secondary (or beta) relaxation process is found in all the materials. The beta process in CNADM has an activation energy (DeltaE(beta)) of about approximately 13.8+/-1 kJmol, and is present even in the corresponding ordered crystalline phase, i.e., in its monoclinic phase. On the other hand, the magnitude of DeltaE(beta) in both the isomers of cyanocyclohexane, i.e., ICNCH and CNCH, is similar and is about 21.1 and 23.4 kJmol, respectively. Unlike CNADM, the cyclohexane derivatives are capable of exhibiting additional intramolecular process due to chair-chair conversion (i.e., in addition to the rotational motion of the side group- C[Triple Bond]N or- N[Triple Bond]C). Therefore, the secondary process of these systems is compared to that occuring in the binary liquid glass formed by dispersing a small quantity of these dipolar liquids in nearly nonpolar orthoterphenyl (OTP). Measurements were also made in the supercooled binary mixures of other cyclohexyl derivatives like cyclohexylchloride and cyclohexylbromide with OTP which lack a flexible side group. The sub-T(g) relaxation process exhibited in all these cases have almost similar activation energy as in case of pure ICNCH and CNCH. These observations together with the fact that the activation energy for this process is much below that of chair-chair conversion which is about 43 kJmol leads us to the conclusion that sub-T(g) relaxation process in the binary mixtures is JG type, and perhaps beta relaxation process in phase I of ICNCH and CNCH is also similar. With the help of semiemperical calculations of the dipolemoments for the axial and equitorial confirmers, it is concluded that the process associated with the chair-chair may not be dielectrically very active and, hence, should be relatively weaker in magnitude. The beta process in CNADM has an activation energy (DeltaE(beta)) of about 13.8+/-1 kJmol, and is present even in the corresponding ordered crystalline phase indicating that it may not be characteristic of the glass formation of phase I. The molecular structure of CNADM is such that it does not possess other intramolecular degrees of freedom of the type equitorial to axial (or chair-chair) transformation. Our experimental finding that JG relaxation for CNADM dispersed in glassy OTP matrix is about 31 kJmol, indicating that the well ...

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Ultrasonic Relaxation and Axial—Equatorial Isomerization in Methylcyclohexane. II

Cited by 28 publications

References 13 publications

On the features of the dielectric response of supercooled ethylcyclohexane

On the features of the dielectric response of supercooled ethylcyclohexane

Conformational stability of chlorocyclohexane from temperature-dependent FT-IR spectra of xenon solutions, r 0 structural parameters, and vibrational assignment

Study of secondary relaxation in disordered plastic crystals of isocyanocyclohexane, cyanocyclohexane, and 1-cyanoadamantane

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