PMID- 32054023
OWN - NLM
STAT- MEDLINE
DCOM- 20201120
LR  - 20201120
IS  - 1422-0067 (Electronic)
IS  - 1422-0067 (Linking)
VI  - 21
IP  - 4
DP  - 2020 Feb 11
TI  - Accurate Diels-Alder Energies and Endo Selectivity in Ionic Liquids Using the 
      OPLS-VSIL Force Field.
LID - 10.3390/ijms21041190 [doi]
LID - 1190
AB  - Our recently developed optimized potentials for liquid simulations-virtual site 
      ionic liquid (OPLS-VSIL) force field has been shown to provide accurate bulk 
      phase properties and local ion-ion interactions for a wide variety of 
      imidazolium-based ionic liquids. The force field features a virtual site that 
      offloads negative charge to inside the plane of the ring with careful attention 
      given to hydrogen bonding interactions. In this study, the Diels-Alder reaction 
      between cyclopentadiene and methyl acrylate was computationally investigated in 
      the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF(6)], 
      as a basis for the validation of the OPLS-VSIL to properly reproduce a reaction 
      medium environment. Mixed ab initio quantum mechanics and molecular mechanics 
      (QM/MM) calculations coupled to free energy perturbation and Monte Carlo sampling 
      (FEP/MC) that utilized M06-2X/6-31G(d) and OPLS-VSIL gave activation free energy 
      barriers of 14.9 and 16.0 kcal/mol for the endo-cis and exo-cis Diels-Alder 
      reaction pathways, respectively (exptl. DeltaH(double dagger) of 14.6 kcal/mol). The endo 
      selectivity trend was correctly predicted with a calculated 73% endo preference. 
      The rate and selectivity enhancements present in the endo conformation were found 
      to arise from preferential hydrogen bonding with the exposed C4 ring hydrogen on 
      the BMIM cation. Weaker electronic stabilization of the exo transition state was 
      predicted. For comparison, our earlier +/-0.8 charge-scaled OPLS-2009IL force field 
      also yielded a DeltaG(double dagger) of 14.9 kcal/mol for the favorable endo reaction pathway but 
      did not adequately capture the highly organized solvent interactions present 
      between the cation and Diels-Alder transition state.
FAU - Velez, Caroline
AU  - Velez C
AD  - Department of Chemistry, University of Miami, Coral Gables, FL 33146, USA.
FAU - Doherty, Brian
AU  - Doherty B
AD  - Department of Chemistry, University of Miami, Coral Gables, FL 33146, USA.
FAU - Acevedo, Orlando
AU  - Acevedo O
AD  - Department of Chemistry, University of Miami, Coral Gables, FL 33146, USA.
LA  - eng
GR  - CHE-1562205/National Science Foundation/
PT  - Journal Article
DEP - 20200211
PL  - Switzerland
TA  - Int J Mol Sci
JT  - International journal of molecular sciences
JID - 101092791
RN  - 0 (1-butyl-3-methylimidazolium hexafluorophosphate)
RN  - 0 (Acrylates)
RN  - 0 (Cyclopentanes)
RN  - 0 (Imidazoles)
RN  - 0 (Ionic Liquids)
RN  - WC487PR91H (methyl acrylate)
SB  - IM
MH  - Acrylates/*chemistry
MH  - Cycloaddition Reaction/methods
MH  - Cyclopentanes/*chemistry
MH  - Imidazoles/*chemistry
MH  - Ionic Liquids/*chemistry
MH  - Models, Molecular
MH  - Quantum Theory
MH  - Thermodynamics
PMC - PMC7072795
OTO - NOTNLM
OT  - Diels-Alder
OT  - FEP
OT  - Force Field
OT  - Monte Carlo
OT  - OPLS
OT  - QM/MM
OT  - ionic liquids
COIS- The authors declare no conflict of interest. The funders had no role in the 
      design of the study; in the collection, analyses, or interpretation of data; in 
      the writing of the manuscript, or in the decision to publish the results.
EDAT- 2020/02/15 06:00
MHDA- 2020/11/21 06:00
PMCR- 2020/02/01
CRDT- 2020/02/15 06:00
PHST- 2020/01/22 00:00 [received]
PHST- 2020/02/06 00:00 [revised]
PHST- 2020/02/08 00:00 [accepted]
PHST- 2020/02/15 06:00 [entrez]
PHST- 2020/02/15 06:00 [pubmed]
PHST- 2020/11/21 06:00 [medline]
PHST- 2020/02/01 00:00 [pmc-release]
AID - ijms21041190 [pii]
AID - ijms-21-01190 [pii]
AID - 10.3390/ijms21041190 [doi]
PST - epublish
SO  - Int J Mol Sci. 2020 Feb 11;21(4):1190. doi: 10.3390/ijms21041190.