Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
On the possibility of catalytic reduction of carbonyl moieties with tris(pentafluorophenyl)borane and H2: a computational study
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
2009 (engelsk)Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, nr 29, s. 5780-5786Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The study thoroughly examines the Gibbs free energy surfaces of a new mechanism for redn. of ketones/aldehydes by tris(pentafluorophenyl)borane (1) and H2. Key elements of the proposed mechanism are the proton and the hydride transfer steps similar to Stephan's catalytic redn. of imines by 1. The proton is transferred to the ketone/aldehyde in the process of H2 cleavage by the carbonyl-borane couple and the hydride is transferred in a nucleophilic attack on the carbonyl carbon by the hydridoborate in the ionic pair, [HOCRR']+[HB(C6F5)3]-. The in solvent Gibbs free energy barriers of H2 splitting by adducts of B(C6F5)3 with acetone, acetophenone and benzaldehyde are predicted to be in the range of 24.5 ± 2.5 kcal mol-1, which corresponds to potential energy barriers in the range of 17.0 ± 2.0 kcal mol-1. Significantly lower barrier of H2 activation is predicted in cases of bulky ketones such as 2,2,4,4-tetramethylpentan-3-one. With respect to the hydridoborate intermediate, the nucleophilic attack on the activated carbon is predicted to have a relatively low barrier for the sterically unhindered substrates, while this barrier is considerably higher for the sterically encumbered substrates. Since the formation of the hydridoborate intermediates is found to be endothermic, the transition state of the nucleophilic attack is the highest point of the computed energy profile for all tested substrates. Overall, according to in solvent d. function calcns. the proposed redn. of "compact" ketones/aldehydes by 1 and H2 is allowed both thermodynamically and kinetically at elevated temp., but it is expected to be slower and more substrate specific than the corresponding redn. of imines. [on SciFinder(R)]

sted, utgiver, år, opplag, sider
The Royal Society of Chemistry , 2009. nr 29, s. 5780-5786
HSV kategori
Identifikatorer
URN: urn:nbn:se:su:diva-30237DOI: 10.1039/b905137fISI: 000267981000024OAI: oai:DiVA.org:su-30237DiVA, id: diva2:242255
Merknad
CAPLUS AN 2009:849255 (Journal)Tilgjengelig fra: 2009-10-07 Laget: 2009-10-07 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. Theoretical modeling of metal- and enzyme catalyzed transformations
Åpne denne publikasjonen i ny fane eller vindu >>Theoretical modeling of metal- and enzyme catalyzed transformations
2010 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis is focused on describing and predicting catalytic reactions. The major part of the work is based on density functional theory (DFT). In some cases where the size of the investigated system precluded the use of more accurate methods molecular dynamics was employed. In several cases the proposed mechanism was later tested in the laboratory. A few examples where the predictions were confirmed are:

  • The formation of an acyl intermediate in the activation of a ruthenium catalyst used for racemizing alcohols. This intermediate was observed by both NMR and in situ FT-IR.
  • The improvement of the substrate specificity and catalytic activity of Candida antarctica lipase A by modifying amino acids close to the active site.
  • The improved specificity of Candida antarctica lipase B toward δ-substituted secondary alcohols by an enzyme variant where the alanine in position 281 was exchanged for a serine.

In other cases experimental results were complemented with a theoretical investigation, for example:

  • The observed second order rate constant for a ruthenium based catalyst used for water oxidation was explained and a novel intramolecular mechanism based on a high valent ruthenium dimer was suggested.
  • The effects of electron withdrawing/donating axial ligands on the performance of ruthenium catalyzed water oxidation were addressed.
  • Mechanisms of H2 activation by Lewis acid/Lewis base adducts were rationalized. One example of the predictive power of computational chemistry is the mechanism of hydrogen uptake by phosphanylboranes; the potential energy barrier for the transition state could be predicted within a few kcal/mol based on the orbital energies of the starting material.
sted, utgiver, år, opplag, sider
Stockholm: Department of Organic Chemistry, Stockholm University, 2010. s. 96
Emneord
density functinal theory, computational chemistry, directed evolution, enzyme, mechanistic studies, catalysis, ruthenium, hydrogen transfer, racemization, artificial photosynthesis, frustrated lewis pairs, hydrogen storage
HSV kategori
Forskningsprogram
organisk kemi
Identifikatorer
urn:nbn:se:su:diva-38344 (URN)978-91-7447-063-5 (ISBN)
Disputas
2010-05-12, Magnelisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Merknad
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 8: In press.Tilgjengelig fra: 2010-04-20 Laget: 2010-04-08 Sist oppdatert: 2010-05-28bibliografisk kontrollert

Open Access i DiVA

Fulltekst mangler i DiVA

Andre lenker

Forlagets fulltekst

Søk i DiVA

Av forfatter/redaktør
Nyhlén, JonasPrivalov, Timofei
Av organisasjonen
I samme tidsskrift
Dalton Transactions

Søk utenfor DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric

doi
urn-nbn
Totalt: 151 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf