METHANIMINE AT HIGH SPATIAL RESOLUTION IN SGR B2: IMPLICATIONS FOR THE FORMATION OF CYANOMETHANIMINE...

METHANIMINE AT HIGH SPATIAL RESOLUTION IN SGR B2: IMPLICATIONS FOR THE FORMATION

OF CYANOMETHANIMINE

Amanda Steber1, Joanna F. Corby2, Nathan A. Seifert1, Cristobal Perez1, Anthony Remijan3, Brooks H. Pate1

1Department of Chemistry, The University of Virginia, Charlottesville, VA 22904

2Department of Astronomy, The University of Virginia, Charlottesville, VA 22904

3AL MA, National Radio Astronomy Observatory, Charlottesville, VA 22904

Previous Results

• Discharge of NH3 and CH3CN• Cyanomethanimine was discovered in

the ISM using the broadband reaction screening process

• Three isomers of cyanomethanimine – Z- isomer: ma=1.35(10)D & mb=0.4(5)D

– E- isomer: ma=3.25(2)D & mb=2.51(2)D

– N- isomer: ma=4.6D & mb= ~1.5D

D.P. Zaleski et al. Ap. J. Lett., 2013, 765, L10

E = 2653 cm-1

E = 39 cm-1

E = 0 cm-1

I. W. M. Smith, D. Talbi, E. Herbst. Astron. Astrophys., 2001, 369, 611.

Direct HCN Dimerization

Protonation

M. Yim, J. Choe. Chem. Phys. Lett., 2012, 538, 24.

314 kJ/mol

-327 kJ/mol

483 kJ/molDischarge Reaction

•CN addition

• The Kaiser group (among others) has focused on the formation of cyanides through the reaction of •CN with olefins– Crossed molecular beam experiments– Methylacetylene, allene, ethylene, dimethylacetylene, etc…

• The radical attacks the p electron density of the hydrocarbon

• They have been able to determine that the neutral – radical reaction occurs with out an activation barrier

N. Balucani et al. Astrophys. J., 2000, 545, 892.

N. Balucani et al. Astrophys. J., 2000, 545, 892.

Could This Work for Cyanomethanimine?

X = N

X = E

(X)-cyanomethanimine

X = Z E = 0 cm-1

E = 39 cm-1

E = 2653 cm-1

Laboratory vs GBT

R. A. Gaume et al. Astrophys. J., 1995, 449, 663.

Pink – Methanimine (absorption)Green – CH2CN (absorption)

Pink – MethanimineGreen – CH2CNBlue– E-cyanomethanimine

(absorption)

GBT PRIMOS Data

J. M. Hollis, A. J. Remijan, P. R. Jewell, F. J. Lovas, J. F. Corby, GBT PRIMOS, http://www.cv.nrao.edu/~aremijan/PRIMOS/.

Blue – Methanimine 35 GHz (Emission)

Pink – Methanimine 33 GHz (Absorption)

Dashed contour – AbsorptionSolid contour - Emission

2 hour observation with 1 hour on source

Conclusions

• Previously proposed reaction mechanisms for the formation of cyanomethanimine in the interstellar medium are not very feasible

• The addition of •CN to methanimine would yield cyanomethanimine + H through a barrierless reaction

• The high resolution spatial maps show that this could be happening as all three species reside in the same spatial locations

• The complex chemistry is suggested to be occurring outside of the hotcore (LMH)

Acknowledgements

• Pate Lab• NRAO• NSF

– Centers for Chemical Innovation Award Number 0847919

– Chemistry Award Number 1213200