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 Astrochemistry
Photolysis Reactions
•OH + H
H2O + hn
H2 + O
CH3OH + hn
•CH OH
2
•CH
3
+ •OH
CH3O• + H
•CH OH + H
2
•NH +
2
NH3 + hn
Radical-Radical Recombination Reactions
CH2(OH)2
CH3O• + •CH2OH
CH3OCH2OH
•CH OH + •NH
2
2
NH2CH2OH
H
CH2(OH)2
• CH O
3
CH3OH
CH3OCH2OH
H
hn
+ •OH
HO •
H
CO
• CH
3
CO
HO •
H2O
NH3
H2CO
HCO •
• CH OH
2
• NH
2
NH2CH2OH
Garrod, Widicus Weaver, & Herbst, Ap. J. 682 (2008) 283-302
Prebiotic Astrochemistry
Photolysis Reactions
•OH + H
H2O + hn
H2 + O
CH3OH + hn
•CH OH
2
•CH
3
+ •OH
CH3O• + H
•CH OH + H
2
•NH +
2
NH3 + hn
Radical-Radical Recombination Reactions
CH2(OH)2
CH3O• + •CH2OH
CH3OCH2OH
•CH OH + •NH
2
2
NH2CH2OH
H
CH2(OH)2
• CH O
3
CH3OH
CH3OCH2OH
H
hn
+ •OH
HO •
H
CO
• CH
3
HO •
H2O
NH3
H2CO
CO
HCO •
• CH OH
2
• NH
2
NH2CH2OH
Garrod et. al. Ap. J. 682 (2008) 283-302
Prebiotic Astrochemistry
•Ices evaporate, releasing molecules
into the interstellar medium
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
CH3OH2+
HCOOH
or H3+
-H2O
aminomethanol
protonated
aminomethanol
glycine
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
1.968 eV energy
O(1D)
E
O(3P)
Chang and Lin, Chem. Phys. Lett. 363 (2002) 175-181
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)
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)
aminomethanol
O(1D)
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
O(1D) + methanol
2.68
methanediol
0.00
Hydroxyl wag ~ 1689 cm-1
Constant
A (GHz)
B (GHz)
C (GHz)
μX (Debye)
μY (Debye)
μZ (Debye)
Methanediol
41.91280
10.19118
9.033043
0.0091
-0.0479
0.0047
Methoxymethanol
O(1D) + dimethylether
2.64
2.05
methoxymethanol
0.00
Constant
Methoxymethanol
A (GHz)
B (GHz)
C (GHz)
μX (Debye)
μY (Debye)
μZ (Debye)
17.15679
5.623778
4.851683
-0.2413
0.0933
-0.1648
Methyl rotor ~ 669 cm-1
Hydroxyl wag ~ 1697 cm-1
Aminomethanol and
n-methylhydroxylamine
O(1D) + methylamine
41.9
0.00
4.36
38.4
n-methylhydroxylamine
aminomethanol
0.78
0.29
Aminomethanol
Constant
Aminomethanol
A (GHz)
B (GHz)
C (GHz)
μX (Debye)
38.6930
9.5457
8.5868
-0.377
μY (Debye)
-0.995
μZ (Debye)
1.341
Amine wag ~2140 cm-1
Hydroxyl wag ~684 cm-1
N-methylhydroxylamine
Constant
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
Methyl rotor ~1384 cm-1
Hydroxyl wag ~2405 cm-1
V3 barrier
predicted = 1384 cm-1
experimentall = 1243 cm-1
i. Sung and Harmony, J. Mol. Spec. 74, 228-241 (1979)
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 PerrySee Carroll
et al. FC04
multipass coupled to
submm source
• Detection within a
supersonic expansion
using double modulation
lock-in amplification
scheme
Possible O(1D) Insertion Sources
N2O
185 nm
O(1D)
CH3OH + Ar
• Larger initial number density
• Low absorption coefficient
• Methanol also absorbs at 185 nm,
necessitating fast mixing
• Small spot to focus UV lamp
Interaction
region
O3 + CH3OH + Ar
• Small initial number density
• Large absorption coefficient
• Methanol does not absorb at 253 nm, 253 nm
no fast mixing necessary
• Focus UV at throat of the expansion
Interaction
region
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