galen sedo, jamie doran, jane curtis, kenneth r. leopold department of chemistry, university of...
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Galen SedoGalen Sedo, Jamie Doran, Jane Curtis, Kenneth R. Leopold, Jamie Doran, Jane Curtis, Kenneth R. Leopold
Department of Chemistry, University of MinnesotaDepartment of Chemistry, University of Minnesota
A Microwave Study of theA Microwave Study of the
HNOHNO33-(H-(H22O)O)33 Tetramer Tetramer
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Fundamentally…
• We know that for a strong acid, like HNO3, the following is true.
• The question becomes: How much water does it take to ionize one HNO3 molecule?
HNO3(g) + H2O() H3O+(aq) + NO3(aq)
H2O()
Atmosphere…
• Troposphere -- acid rain, and ammonium nitrate aerosol
-- reservoir for NOx and HOx species
• Stratosphere -- Polar Stratospheric Clouds (PSC’s)
-- polar ozone depletion
Nitric Acid HydratesNitric Acid Hydrates
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(1) HNO3-H2O(2) HNO3-(H2O)2
Nitric Acid HydratesNitric Acid Hydrates
1. Canagaratna, M.; Ott, M.E.; Leopold, K.R. "The Nitric Acid - Water Complex: Microwave Spectrum, Structure, and Tunneling.“ J. Phys. Chem. A 1998, 102, 1489-1497.
2. Craddock, M. B.; Brauer, C. S.; Leopold, K. R. “Microwave Spectrum, Structure, and Internal Dynamics of the Nitric Acid Dihydrate Complex” manuscript in preparation.
• Complete experimental gas-phase structure
• Experimental 14N Quadrapole Coupling Constants
• Insight into the internal dynamics of the water sub-units
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Nitric Acid Tri-hydrate, HNONitric Acid Tri-hydrate, HNO33 – (H – (H22O)O)33
1. Taesler, I.; Delaplane, R. G.; Olovsson, I. Acta Cryst. 1975, B31, 1489.
• Refined the crystal structure of Luzzati et al. (1953).
2. Ritzhaupt, G.; Devlin, J. P. J. Phys. Chem. 1991, 95, 90.
• FTIR investigations of thin crystalline films, HNO3-(H2O)n n = 1-3
3. McCurdy, P. R.; Hess, W. P.; Xantheas, S. S. J. Phys.Chem. A 2002, 106, 7628-7635.
• MP2/aug-cc-pVDZ geometry optimization of the 10-Member Ring confirmation
• Fourier transform infrared (FTIR) spectra for smaller nitric acid complexes
4. Escribano, R.; Couceiro, M.; Gomez, P. C.; Carrasco, E. Moreno, M. A.; Herrero, V. J. J. Phys. Chem. A 2003, 107, 651-661.
• B3LYP/aug-cc-pVTZ geometry optimizations of both the 10- and 8-Member Ring confirmations
• Reflection-absorption infrared (RAIR) spectra
5. Scott, J. R.; Wright, J. B. J. Phys. Chem. A 2004, 108, 10578-10585.
• MP2 and B3LYP geometry optimizations using the 6-311++G(2d,p) basis for both the 10- and 8-Member Ring confirmations
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10-Member Ring: Top View
10-Member Ring: Side View
8-Member Ring: Top View
8-Member Ring: Side View
Ebinding [kcal/mol] Method/Basis Ebinding [kcal/mol]
-22.7 MP2/6-311++G(2df,2pd) *this work* -22.4(+0.3)
-31.6(+0.4) MP2/6-311++G(2d,p) Scott et al. -32.0
-29.7 B3LYP/6-311++G(2d,p) Scott et al. -29.6(+0.1)
-20.5 B3LYP/aug-cc-pVTZ Escribano et al. -19.7(+0.8)
Theoretical Structures of the HNOTheoretical Structures of the HNO33-(H-(H22O)O)33 Tetramer Tetramer
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Mirror
Antenna
Argon bubbled through a sample of 90% HNO3
Backing Pressure 2–3 atm
Microwave
Electronics
Computer
14732.5 14733 14733.5 14734 14734.5 14735
Frequency (MHz)Spectrum
Fabry-Perot Cavity
Diffusion Pump
Pulsed
Nozzle
Mirror
The Pulsed Nozzle FTMW Spectrometer
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Mirror
Antenna
Argon bubbled through a sample of 90% HNO3
Backing Pressure 2–3 atm
Microwave
Electronics
Computer
14732.5 14733 14733.5 14734 14734.5 14735
Frequency (MHz)Spectrum
Fabry-Perot Cavity
Diffusion Pump
Pulsed
Nozzle
Mirror
The Pulsed Nozzle FTMW Spectrometer
Series 9PulsedSolenoidValve
Needle Adaptor
• Stainless Steal Needle Dimensions ID = 0.016" Length = 0.205"
• Argon bubbled through H2O at a rate of 1 sccm.
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2,000 gas-pulses / 20,000 FID’s
Intensity = 0.09
1,000 gas-pulses / 6,000 FID’s
Intensity = 0.06
H15NO3-(H2O)3
404 - 303
7246.500 7246.750 7247.000 7247.250 7247.500
Frequency [MHz]
HNOHNO33-(H-(H22O)O)33 Spectra Spectra
HNO3 Intensity ≈ 18,000
HNO3–H2O Intensity ≈ 500
HNO3–(H2O)2 Intensity ≈ 5.0
H14NO3-(H2O)3
404 -303
7273.750 7274.000 7274.250 7274.500 7274.750
Frequency [MHz]
CavityFrequency
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H15NO3-(H2O)3
423 - 322
7937.750 7938.000 7938.250 7938.500 7938.750
Frequency [MHz]
HNOHNO33-(H-(H22O)O)33 Spectra Spectra
2,000 gas-pulses / 20,000 FID’s
Intensity = 0.12
1,000 gas-pulses / 6,000 FID’s
Intensity = 0.12
H14NO3-(H2O)3
423 - 322
7976.000 7976.250 7976.500 7976.750 7977.000
Frequency [MHz]
CavityFrequency
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Nitric Acid Tri-hydrate Molecular ConstantsNitric Acid Tri-hydrate Molecular Constants
H14NO3-(H2O)3 : 74 Assigned Transitions, K-1 = 0 – 4
H15NO3-(H2O)3 : 18 Assigned Transitions, K-1 = 0 – 2
DNO3-(H2O)3 : 18 Assigned Transitions, K-1 = 0 – 2
H14NO3-(H2O)3 H15NO3-(H2O)3 DNO3-(H2O)3
A 2269.2963(32) 2268.390(12) 2246.496(16)B 1215.91162(26) 1209.0226(11) 1210.2466(19)C 798.28665(21) 795.19692(67) 792.9304(10)D
J 0.0010555(26) 0.001054(12) 0.001091(13)D
JK -0.002263(24) -0.00234(15) -0.00281(20)d
j 0.0004093(17) 0.0004102(81) 0.0004267(67)
dk 0.000831(36) 0.000831b 0.000831b
caa -0.7991(87) ---------- ----------
cbb-ccc 0.388(38) ---------- ----------k -0.432 -0.438 -0.426
b Parameter was fixed at the parent value in the final fit.
Spectroscopic Constants for HNO3-(H2O)3a
a All values, except the asymmetry parameter (k), are in MHz
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Comparison of the Theoretical andComparison of the Theoretical and
Experimental ResultsExperimental Results10-Member Ring: Top View
10-Member Ring: Side View
8-Member Ring: Top View
8-Member Ring: Side View
Dexp-theo
Dexp-theo
9.346 A [MHz] -197.057-6.045 B [MHz] 16.4851.569 C [MHz] -85.123
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Comparison of the Theoretical andComparison of the Theoretical and
Experimental ResultsExperimental Results
14N → 15N Isotope Shifts
10-Member Ring: Top View 8-Member Ring: Top View
Dn [MHz] Dn/nparent
Dn [MHz] Dn/nparent
Experimental 27.216 0.0037 32.805 0.003710-Member Ring 27.177 0.0037 32.836 0.00378-Member Ring 36.399 0.0046 43.014 0.0045
303 → 404 404 → 505
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Comparison of the Theoretical andComparison of the Theoretical and
Experimental ResultsExperimental Results
DNO3 Isotope Shifts
10-Member Ring: Top View 8-Member Ring: Top View
Dn [MHz] Dn/nparent
Dn [MHz] Dn/nparent
Experimental 49.416 0.0068 60.305 0.006810-Member Ring 33.350 0.0046 40.643 0.00468-Member Ring 10.718 0.0014 13.161 0.0014
303 → 404 404 → 505
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1414N Quadrupole Coupling ConstantsN Quadrupole Coupling ConstantsNitrate IonNitrate Ion
eQq = 0.656 MHz1
1. Adachi, A.; Kiyoyama, H.; Nakahara, M.; Masuda, Y.; Yamatera, H.; Shimizu, A.; Taniguchi, Y. J. Chem. Phys. 1989, 90, 392.
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1414N Quadrupole Coupling ConstantsN Quadrupole Coupling ConstantsNitric Acid HydratesNitric Acid Hydrates
eQqNitrate Ion ↔ ccc
c
a
b
HNO3-H2O
a
b
c
HNO3-(H2O)2
a
b
c
HNO3-(H2O)3
caa + cbb + ccc = 0
ccc = ־½[caa + (cbb - ccc)]
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HNO3-H2O HNO3-(H2O)2HNO3-(H2O)3
Proton Transfer in Nitric Acid SystemsProton Transfer in Nitric Acid Systems
Solvent Water Molecules vs. ccc
0.0
0.2
0.4
0.6
0 1 2 3 4
Solvent Water Molecules
ccc
Hydrates
Nitrate Ion (aq)
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Dr1(OH) – Dr2(H···O)• The parameter rho () has been devisedc to quantify proton transfer in hydrogen bonded systems.
• Dr1(OH) = Stretch in O-H covalent bond relative to covalent bond in free HNO3 monomer.
• Dr2(H···O) = Stretch in hydrogen bond relative to O–H bond distance in hydronium ion (H3O+).
> 0 indicates proton transfer.
= 0 indicates equal sharing of proton.
< 0 indicates neutral pair.
Proton Transfer in HNOProton Transfer in HNO33 Complexes Complexes
c Kurnig, I. J.and Scheiner, S. Int. J. Quantum Chem., QBS 1987, 14, 47.
H
O
H
H H ONO2
r1(OH)r2(O---H)
Dr1(OH)
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HNO3-H2O HNO3-(H2O)2HNO3-(H2O)3
Solvent Water Molecules vs. Proton Transfer
-1.00
-0.75
-0.50
-0.25
0.00
0 1 2 3 4
Solvent Water Molecules
Computational
Experimental
Proton Transfer in Nitric Acid SystemsProton Transfer in Nitric Acid Systems
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The Degree of Proton Transfer vs. ccc
0.0
0.2
0.4
0.6
-1.00 -0.75 -0.50 -0.25 0.00
c cc
Computational
Experimental
Nitrate Ion (aq)
(1) HNO3-H2O (2) HNO3-(H2O)2(3) HNO3-(H2O)3
12
3
Proton Transfer in Nitric Acid SystemsProton Transfer in Nitric Acid Systems
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(4) HNO3-(H2O)3
(5) HNO3-N(CH3)3(1) HNO3-H2O
The Degree of Proton Transfer vs. ccc
0.0
0.2
0.4
0.6
-1.00 -0.75 -0.50 -0.25 0.00
c cc
Computational
Experimental
Nitrate Ion (aq)
All
Linear (All)
(3) HNO3-(H2O)2(2) HNO3-NH3
12
3
4
5
Proton Transfer in Nitric Acid SystemsProton Transfer in Nitric Acid Systems
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ConclusionsConclusions
1. Spectra for three isotopes were observed
• Rotational Constants and the isotopic shifts indicate the spectra are those of the 10-Member Ring confirmation
2. The Potential Energy Surface of the HNO3-(H2O)2 system has been
performed using MP2/6-311++G(2pd,2df)
• The Global Minimum was found to be a 10-Member Ring
• An 8-Member Ring local minimum was also calculated
3. The degree of proton transfer was assessed using the experimental 14N Quadrupole coupling and the theoretical structure.
• Both methods suggest an increase in proton transfer when compared with the mono- and di-hydrate.
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Funding
• National Science Foundation (NSF)
• Petroleum Research Fund (PRF)
• Minnesota Supercomputing Institute (MSI)
• Dr. Kenneth Leopold
Acknowledgements
• Dr. Matthew Craddock
• Dr. Carolyn Brauer
• Jamie Doran
• Jane Curtis