Joshua M. Blechle & Erin L. FutrellFaculty Mentor

Dr. Eric V. Patterson

Examination of theHydroperoxidolysis of a

VX Model Compound

VX Facts

• Discovered by various groups in1952-53

• It is mistaken by the body to beacetylcholine, a neurotransmitter thatcauses muscles to contract

• Previous research has shown that VX isbest neutralized by an attack ofhydroperoxide

Model VX-Compound

O-ethyl S-2-[(diisoproylamino)ethyl]methylphosponothiolate (VX)

O,S-dimethylmethylphosphonothiolate

Previous Research

Oxygen Transfer

• This shift was found to be the pathwayrequiring the least energy

• This, however, is suspect since thetransfer is so unusual

• The goal of this research is to learn moreabout the oxygen transfer and determineits likelihood

Theory

• MPWB1K/6-31+G(d,p) Provides accurate representation of

energies and geometries (quantum)

• Standard quantum chemical resultsare obtained at 0 K

• Thermal energy can be considered byemploying classical moleculardynamics

ADMP Calculations

• Atom-Centered Density Matrix Propagation Treats electrons quantum-mechanically, but

nuclei classically

U is the energy from the quantum calculationGenerates a thermal potential energy surface

!

F = ma = mdv

dt= m

d2x

dt2

= "#

#rU

Gas and Solution Phases

• A gas-phase reaction can have a potential energy surface (PES) thatis very different from the PES of the same reaction in solution

Motivation

• Previous study employed gas-phasegeometries

• Current study employs gas-phaseconditions as well as aqueous conditions.

• Solvation could have significant impact onresults

Gas Phase Results

• The observed outcomes of gas phase TBP Direct P-S cleavage Rearrangement with loss of water Rearrangement with loss of OH group

(possibly additional water)• Only the TBP product was previously

predicted• Suggests a more complicated PES than

originally thought

Trigonal Bipyramidal

To view movie:http://jade6.truman.edu/movies/tbr.mov

Direct P-S Bond Cleavage

To view movie:http://jade6.truman.edu/movies/ps.mov

Formation of H2O

To view movie:http://jade6.truman.edu/movies/water.mov

Gas Phase Summary

One Hundred completed trajectories:

Transition State

TBP

16.0% (16)

H2O45.0% (45)

P-S

33.0% (33)

OH

6.0% (6)

Aqueous Phase Results

• Stationary point calculations have ledto an acceptable transition state

• Frequency calculations were used topinpoint the most stable geometry

• From this, subsequent ADMPcalculations can be performed

• This will follow the same procedure asthe gas phase

Aqueous Transition State

• This is the optimized geometry from whichADMP calculations will start

Goals for the Future

• Using the constructed aqueoustransition state, determine theexistence of the oxygen transfer

• Continue to collect aqueous phasedata using ADMP calculations

• Use combined data to confirm mostprobable mechanism for thehydroperoxidolysis of VX

References andSpecial Thanks

• References Seckute, J.; Menke, J.L.; Emnett, R.J.;

Patterson, E.V.; Cramer, C.J. J. Org. Chem.2005, 70(22), 8649-8660.

• Special Thanks To Dr. Patterson, our faculty mentor,

who has given us this wonderfulopportunity.