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