Sponsor: Professor Vince DeTuri, References from Professor Heinz Koch

• Single Proton Nucleus

• N. Mass: 1.6726x10-27 kg

• Lightest Element

Proton (1.6726x10-27 kg)

Neutron (1.6749x10-27 kg)

• Added Neutron

• N. Mass: 3.3475x10-27 kg

• 200.13% more massive

than Hydrogen Atom.

• Two added Neutrons

• N. Mass: 5.0224x10-27 kg

• 300.28% more massive

than Hydrogen Atom.

• Experimental Observation: Reactions involving Hydrogen transfer go faster than Deuterium transfer, which is faster still than Tritium.

• Hydrogen, deuterium, and tritium have different masses but behave the same electronically.

Energy

• Getting from point A to point B requires Energy.

ΔE

• Deuterium sits lower in energy than Hydrogen, and Tritium sits lower still.

H

D

T

• This means that Hydrogen requires the least ΔE to get over the energy barrier.

• The result is that Hydrogen will transfer the fastest, and these relative rates can be experimentally observed.

B

A

Reaction ProgressXH Y- (X H Y)- X- HY

• Professor Heinz Koch began studying the reaction of certain alkenes with methoxide ion.

The Alkene Benzyl-β,β-difluorostyrene

-

HydrogenCarbonFluorineOxygen

The Alkane

• Proton Transfer: Can study isotope effects…

• However: No isotope effects were observed!

+ (E) & (Z) Isomers

Methoxide/Methanol

• The reaction mechanism can be summarized with a theoretical energy diagram:

The Alkene

(E) & (Z) Isomers

The Alkane

-Carbanion

H-Bonding

Energy

• Organic Chemistry: Make Unexpected Observations

• Cannot observe proton, deuteron, and trition transfer during reactions!

• Can determine kinetic isotope effects through chemical kinetics.

• Physical Chemistry: Model Unexpected Observations• Cannot easily determine reaction rates and kinetic isotope effects.

• Can observe reaction pathways, intermediates, product analysis, and relative energetics!

Reaction Progress

Energy

• Interested only in proton exchange right now.

Too Difficult to Calculate!

• Using b3lyp/6-31g+(d,p) level of theory for optimization to support energy diagram.

Calculate the Optimization Energies of:

Energy Calculations

E

Encounter Complex

Transition State

Hydrogen Bound

0 kJ/mol

14 kJ/mol

30 kJ/mol (approx)

• Many TS calculations crashed; many approximations were made.

• Find an accurate Transition State.• Does the TS connect the EC and HB?

• Build up the solvent system.

• Four Solvating methanol molecules…

• Use solvent wrapping technique.

• Try different solvents.

• Try different carbanion systems.

• Model the actual system.

Pentafluorobenzene 9-Methyl-Fluorene

Sponsor: Professor Vince DeTuri, References from Professor Heinz Koch