Ab Initio

Han, Insuk; Kim, Chang Kon; Jung, Hak Jin; Lee, Ikchoon

doi:10.1007/s002140050147

Cited by 4 publications

(8 citation statements)

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“…59 In solution they are 44 kJ/mol for dimethyl ether and 46 kJ/mol for neat solution. 63 Studies predicting this barrier in solvent are restricted to Abraham and Siverns, 63 Birnstock, 22 Benassi, 62 and In-Suk Han 64 who found that the barriers increased with increasing dielectric constant, as was seen experimentally. The results of Abraham and Han agree closely with experiment.…”

Section: Methodsmentioning

confidence: 92%

Solvent Effects on Internal Rotational Barriers in Furfural. NMR Measurements and ab-Initio Molecular Orbital Methods Using Continuum Models

Bain

Hazendonk

1997

J. Phys. Chem. A

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Modern experimental and theoretical methods for determining solvent effects on internal rotational barriers in small molecules are compared. The barrier to rotation of the aldehyde group in furfural dissolved in toluene, acetone, and methanol is used as a test case. Ab-initio molecular orbital methods such as self consistent reaction field (SCRF) calculations, performed with the Onsager and isodensity surface polarized continuum (IPC) model, predict an increase in barrier with increasing solvent dielectric constant, ε. A combination of three nuclear magnetic resonance experiments are used to obtain rate data over 6 orders of magnitude representing an approximately 150 K temperature range. Activation parameters were obtained with errors less than 1 kJ/mol and 6 J/(mol K) for ΔH ⧧ and ΔS ⧧, respectively. In acetone and toluene large ΔS ⧧ values of −26 and 20 J/(mol K) were found, along with a ΔS° of 10 J/(mol K) in both solvents. In methanol no appreciable values for ΔS ⧧ and ΔS° were measured. The ΔH ⧧ for toluene, acetone, and methanol are 48.6, 40.2, and 46.4 kJ/mol, respectively, which do not obey a simple relationship with ε. This indicates that the solvent effect is likely more complex than just the effect of a solvent reaction field. The large ΔS ⧧ values support this and also imply that equating ΔG ⧧ and ΔH ⧧ is not always justified, even for aprotic solvents. The behavior of these three barriers and their corresponding ΔS ⧧ are discussed in terms of direct solvent−solute interactions.

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Section: Methodsmentioning

confidence: 92%

Solvent Effects on Internal Rotational Barriers in Furfural. NMR Measurements and ab-Initio Molecular Orbital Methods Using Continuum Models

Bain

Hazendonk

1997

J. Phys. Chem. A

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“…Preparation of [Cp * Rh(g 6 -2,6-(Me 2 CH) 2 C 6 H 3 NH 2 )]-(OTf) 2 (1) As mentioned in Section 2, the cationic Cp * Rh-aniline complex 1 could be prepared in two ways (Scheme 1). In the first method, the commercially available [Cp * Rh(lCl)Cl] 2 is converted to [Cp * Rh(NO 3 )(OTf)] [30] by the two-step addition of AgNO 3 and AgOTf, which is subsequently treated with 2,6-diisopropylaniline to give complex 1 in 53% yield. The second method starts from [Cp * Rh(O-H 2 ) 3 ](OTf) 2 [31], which can be prepared from [Cp * Rh(lCl)Cl] 2 in high yield just in a single step.…”

Section: Resultsmentioning

confidence: 99%

“…The starting complex [Cp * Rh(g 6 -C 6 H 3 NH 2 -2,6-i-Pr 2 )](OTf) 2 (1) was prepared from either [Cp * Rh(g 2 -NO 3 )(g 1 -OTf)] [30] or [Cp * Rh(OH 2 ) 3 ](OTf) 2 [31]. 1 H, 13 …”

Section: Methodsmentioning

confidence: 99%

Reactivity of [Cp∗Rh(η6-C6H3NH2-2,6-i-Pr2)](OTf)2 toward phosphines and alkynes

Lim¹,

Baeg²,

Lee³

2006

Journal of Organometallic Chemistry

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“…The energy differences for the sulfur and selenium analogues are close to each other and this may be due to the comparable dipole moments of their rotamers. The behaviour of the rotamers of the title compounds in different solvents has also been noted for other related compounds [19].…”

Section: Oy-syn-rotamermentioning

confidence: 94%

“…Han et al [19] studied the rotational equilibria of 2-substituted furan and thiophene carbonyl derivatives in the gas and solution phases using ab initio methods. They found that the deciding factor for stability of the syn-and anti-rotamers is the extent and nature, repulsive or attractive, of interaction between the oxygen or sulphur of the furan or thiophene ring with the oxygen of the carbonyl group.…”

Section: Introductionmentioning

confidence: 99%