The Effect of Pressure on Organic Reactions: Basic Principles and Mechanistic Applications

Wurche, Frank; Klärner, Frank‐Gerrit

doi:10.1002/9783527612628.ch02

“…The setup presented here opens up an increased pressure range for stirring of various media and therefore new possibilities for producing novel materials via solvent-based synthesis schemes and chemical reactions. This includes especially hydrothermal conversions and reactions at gigapascal pressures as well as organic reactions in fluids [21][22][23].…”

Section: Discussionmentioning

confidence: 99%

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

Hsu

¹

,

Gordeeva

²

,

Antlauf

³

et al. 2020

High Pressure Research

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A new method for stirring under high pressure conditions has been developed and tested. The key component is a Teflon cell assembly equipped with magnetic stirring function, which is capable to operate across a wide pressure range, up to at least 2 GPa, in a large volume press. The setup enables adjustable stirrer rotation rate and detection of stirring in a sample, e.g. to observe liquidsolid phase transitions at high pressure. The viscosity limit of stirring is ca. 500 times that of water at room temperature (i.e. ∼500 mPas). Moreover, we show that zinc oxide nanoparticles hydrothermally synthesized at 0.5 GPa and 100°C under stirring conditions show an order of magnitude smaller size (100 nm) compared to those synthesized under non-stirring conditions (1 μm). The wide pressure range for stirring of viscous media opens interesting possibilities to produce novel materials via hydrothermal synthesis and chemical reactions.

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“…An empirical packing coefficient was introduced to account for such negligence and to correct the underestimated ∆ ‡ , computed by this method. 15,29 A new method for more rigorous ∆ ‡ calculations is the recently-developed extreme pressure polarizable continuum model (XP-PCM). 30 As an extension of the popular polarizable continuum model (PCM) that tackles molecular solution energies at the standard condition of pressure, the XP-PCM allows for quantum chemical calculations of the energy profiles of chemical reactions under pressure.…”

Section: Concerted [4+2]-ene Pathwaysmentioning

confidence: 99%

“…The effect of pressure on the rate of a chemical reaction is measured by the volume of activation (or activation volume) ∆ ‡ . 5,6,7,8,9,10,11,12,13,14,15,16,17,18 The volume of activation is the volume change of a reaction system from the reactant(s) to the transition state.…”

mentioning

confidence: 99%

High-pressure reaction profiles and activation volumes of 1,3-cyclohexadiene dimerizations computed by the extreme pressure-polarizable continuum model (XP-PCM)

Chen

¹

,

Houk

²

,

Cammi

³

2021

Preprint

0

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Quantum chemical calculations are reported for the thermal dimerizations of 1,3-cyclohexadiene at 1 atm and high pressures up to 6 GPa. Previous experiments [Klärner et al. Angew. Chem. Int. Ed. 1986, 25, 108], based on measured activation energies and activation volumes, suggested concerted mechanisms for the formation of the endo [4+2] cycloadduct and a [6+4]-ene adduct, and stepwise mechanisms for the formation of the exo [4+2] cycloadduct and two [2+2] cycloadducts. Computed activation enthalpies (ωB97XD, CCSD(T) and SC-NEVPT2) of plausible dimerization pathways at 1 atm agree well with the experiment activation energies and the values from previous calculations [Ess et al. J. Org. Chem. 2008, 73, 7586]. High-pressure reaction profiles, computed by the recently-developed extreme pressure-polarizable continuum model (XP-PCM), show that the reduction of reaction barrier is more profound in concerted reactions than in stepwise reactions, which is rationalized on the basis of the volume profiles of different mechanisms. A clear shift of the transition state towards the reactant by high pressure is revealed for the [6+4]-ene reaction by the calculations. The computed activation volumes by XP-PCM agree excellently with the experimental values, confirming the existence of competing mechanisms in the thermal dimerizations of 1,3-cyclohexadiene.

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“…The effect of pressure on the rate of a chemical reaction is measured by the volume of activation (or activation volume) ∆𝑉 ‡ . 5,6,7,8,9,10,11,12,13,14,15,16,17,18 The volume of activation is the volume change of a reaction system from the reactant(s) to the transition state.…”

Section: Introductionmentioning

confidence: 99%

High-pressure reaction profiles and activation volumes of 1,3-cyclohexadiene dimerizations computed by the extreme pressure-polarizable continuum model (XP-PCM)

Chen

¹

,

Houk

²

,

Cammi

³

2021

Preprint

0

View full text Add to dashboard Cite

Quantum chemical calculations are reported for the thermal dimerizations of 1,3-cyclohexadiene at 1 atm and high pressures up to 6 GPa. Previous experiments [Klärner et al. Angew. Chem. Int. Ed. 1986, 25, 108], based on measured activation energies and activation volumes, suggested concerted mechanisms for the formation of the endo [4+2] cycloadduct and a [6+4]-ene adduct, and stepwise mechanisms for the formation of the exo [4+2] cycloadduct and two [2+2] cycloadducts. Computed activation enthalpies (ωB97XD, CCSD(T) and SC-NEVPT2) of plausible dimerization pathways at 1 atm agree well with the experiment activation energies and the values from previous calculations [Ess et al. J. Org. Chem. 2008, 73, 7586]. High-pressure reaction profiles, computed by the recently-developed extreme pressure-polarizable continuum model (XP-PCM), show that the reduction of reaction barrier is more profound in concerted reactions than in stepwise reactions, which is rationalized on the basis of the volume profiles of different mechanisms. A clear shift of the transition state towards the reactant by high pressure is revealed for the [6+4]-ene reaction by the calculations. The computed activation volumes by XP-PCM agree excellently with the experimental values, confirming the existence of competing mechanisms in the thermal dimerizations of 1,3-cyclohexadiene.

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The Effect of Pressure on Organic Reactions: Basic Principles and Mechanistic Applications

Cited by 19 publications

References 142 publications

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

High-pressure reaction profiles and activation volumes of 1,3-cyclohexadiene dimerizations computed by the extreme pressure-polarizable continuum model (XP-PCM)

High-pressure reaction profiles and activation volumes of 1,3-cyclohexadiene dimerizations computed by the extreme pressure-polarizable continuum model (XP-PCM)

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