Computational Study and Laboratory Spectroscopy of Prebiotic Molecules Produced by O( 1 D) Insertion...
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Computational Study and Laboratory Spectroscopy of Prebiotic Molecules Produced by O(1D) Insertion
Reactions
Brian Hays, Bridget Alligood DePrince, and Susanna Widicus Weaver
Emory University
Prebiotic AstrochemistryPhotolysis ReactionsH2O + hn •OH + H
H2 + O
CH3OH + hn •CH3 + •OH CH3O• + H•CH2OH + H
NH3 + hn •NH2 + H
Radical-Radical Recombination Reactions
•CH2OH + •OH CH2(OH)2
CH3O• + •CH2OH CH3OCH2OH
•CH2OH + •NH2 NH2CH2OH
H2O
CO
H2CO
CH3OH
NH3
HO •
CO
HCO •
• CH3O
• NH2
• CH3
• CH2OH
H
H
HO •hn
NH2CH2OH
CH2(OH)2
CH3OCH2OH
Garrod, Widicus Weaver, & Herbst, Ap. J. 682 (2008) 283-302
Prebiotic AstrochemistryPhotolysis ReactionsH2O + hn •OH + H
H2 + O
CH3OH + hn •CH3 + •OH CH3O• + H•CH2OH + H
NH3 + hn •NH2 + H
Radical-Radical Recombination Reactions
•CH2OH + •OH CH2(OH)2
CH3O• + •CH2OH CH3OCH2OH
•CH2OH + •NH2 NH2CH2OH
H2O
CO
H2CO
CH3OH
NH3
HO •
CO
HCO •
• CH3O
• NH2
• CH3
• CH2OH
H
H
HO •hn
NH2CH2OH
CH2(OH)2
CH3OCH2OH
Garrod et. al. Ap. J. 682 (2008) 283-302
Prebiotic Astrochemistry•Ices evaporate, releasing molecules into the interstellar mediumO
C
O
H
HH
C
H
HH
O
HO
H
CH
HCH
H
N
HH
OH
Photo Credit:T.A. Rector and T. Abbott, U. Alaska and NOAO, AURA, NASA . NGC 3582
Prebiotic Astrochemistry•Ices evaporate, releasing molecules into the interstellar medium• Molecules can undergo ion-neutral reactions in the gas phase
O
C
O
H
HH
C
H
HH
O
HO
H
CH
HCH
H
N
HH
OH
aminomethanol glycine protonatedaminomethanol
HCOOH
or H3+
CH3OH2+
-H2OH
HHH N
H
OO
C
CHHH
H N
HO
CH
HHH N
HHO
C
+
Charnley, S. B. 1997, in IAU Colloq. 161, (Bologna: Editrice Compositori), 89
Proposed Formation Route for Laboratory Spectroscopy
• Molecules unstable under terrestrial conditions; no laboratory spectrum available
• Produce these molecules using efficient O(1D) insertion reactions
O(1D) Insertion Reactions• Barrierless reactions
of excited oxygen atoms and closed shell molecules
• Insert into X-H bonds– X= H, C, N
Chang and Lin, Chem. Phys. Lett. 363 (2002) 175-181
1.968 eV energy
E
O(1D)
O(3P)
Products undergo unimolecular dissociation unless excess vibrational energy is quenched
O(1D) Insertion Reactions
• Does O(1D) preferentially insert into N-H or C-H bonds?
O(1D)
HO
H
H
H
NCH
H
H
H
H
C N H
aminomethanol
O(1D) Insertion Reactions
• Does O(1D) preferentially insert into N-H or C-H bonds?
• n-methyl hydroxylamine forms from O(1D) insertion into N-H bond
O(1D)
HO
H
H
H
NCH
H
H
H
H
C N H
O(1D)
H
H
H
C
H
N O
H
H
H
H
H
C N H
aminomethanol
n-methylhydroxylamine
Calculations
• GAUSSIAN 09i using the Emory University Cherry L. Logan Emerson Center for Scientific Computing
• Molecules included: methanediol, methoxymethanol, aminomethanol, n-methylhydroxylamine
• Geometry optimization, torsional barrier energies, dipole moments, conformer energies, and rotational constants using MP2/AUG-cc-pVTZ level of theory
• Spectra predicted with CALPGMii program suite
i. Firsch et. al., Gaussian 09 Revision. 2009 ii. Pickett, J. Mol. Spectrosc. 1991, 148, 371–377
Methanediol
Constant MethanediolA (GHz) 41.91280B (GHz) 10.19118C (GHz) 9.033043μX (Debye) 0.0091μY (Debye) -0.0479μZ (Debye) 0.0047
0.00
2.68
Hydroxyl wag ~ 1689 cm-1
O(1D) + methanol
methanediol
Methoxymethanol
Constant Methoxymethanol
A (GHz) 17.15679B (GHz) 5.623778C (GHz) 4.851683μX (Debye) -0.2413μY (Debye) 0.0933μZ (Debye) -0.1648
0.00
2.64
2.05
Hydroxyl wag ~ 1697 cm-1
Methyl rotor ~ 669 cm-1
O(1D) + dimethylether
methoxymethanol
Aminomethanol and n-methylhydroxylamine
38.441.9
4.360.78 0.290.00
n-methylhydroxylamineaminomethanol
O(1D) + methylamine
AminomethanolConstant Aminomethanol
A (GHz) 38.6930B (GHz) 9.5457C (GHz) 8.5868μX (Debye) -0.377
μY (Debye) -0.995
μZ (Debye) 1.341
Amine wag ~2140 cm-1
Hydroxyl wag ~684 cm-1
N-methylhydroxylamineConstant Calculations Experimentali
A (GHz) 39.1319 38.930771
B (GHz) 10.0320 9.939607
C (GHz) 8.7775 8.690716
μX (Debye) 0.661 0.611
μY (Debye) 0.470 0.366
μZ (Debye) -0.130 (-0.012)1/2 ~0
V3 barrier predicted = 1384 cm-1 experimentall = 1243 cm-1
i. Sung and Harmony, J. Mol. Spec. 74, 228-241 (1979)
Methyl rotor ~1384 cm-1
Hydroxyl wag ~2405 cm-1
Experiment• Direct absorption spectroscopy using Perry multipass coupled to submm source• Detection within a supersonic expansion using double modulation lock-in amplification scheme
Experiment• Direct absorption spectroscopy using Perry multipass coupled to submm source• Detection within a supersonic expansion using double modulation lock-in amplification scheme
See Carroll et al. FC04
Possible O(1D) Insertion Sources
185 nm
CH3OH + Ar
O(1D)
Interaction region
N2O
253 nm Interaction region
O3 + CH3OH + Ar
• Larger initial number density• Low absorption coefficient• Methanol also absorbs at 185 nm, necessitating fast mixing• Small spot to focus UV lamp
• Small initial number density • Large absorption coefficient• Methanol does not absorb at 253 nm, no fast mixing necessary • Focus UV at throat of the expansion
Ozone Spectra
Future Work
• Search for O2(1Δ) as an indicator of O(1D) production
• Optimize insertion mechanism to produce known molecule: CH4+ O(1D) → CH3OH
• Search for target molecules in lab
• Search for molecules in interstellar medium
Acknowledgments• The Widicus Weaver group: Jake Laas, Jay Kroll, & Thomas Anderson• Dr. Michael Heaven for helpful discussions• Dr. Brooks Pate for loan of equipment• Cherry L. Logan Emerson Center for
Scientific Computing• NASA APRA Grant NNX11AI07G• NASA Herschel OT1 Analysis Program RSA
No. 1428755