Image from www.nasa.gov

Studies of Cyanoacetylene Oligomers:

Cyano-SubstitutedCyclobutadienes,

Dewar-Benzenes, and Benzenes

Jessica L. MenkeRobert J. McMahon—University of Wisconsin, Madison

Henning Hopf—Technische Universität Braunschweig, Braunschweig, GermanyJens-Uwe Grabow—Gottfried-Wilhelm-Leibniz-Universität, Hannover, Germany

Midwest Astrochemistry MeetingUniversity of Illinois November 8, 2008

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Herbst, E. J. Phys. Chem. A 2005, 109, 4017; Young, Y. L. Icarus 1987, 72, 468;Strobel, D. F. Int. Rev. Phys. Chem. 1983, 3, 145; Mizutani, H. Origins of Life 1975, 6, 513;

Becker, R. S.; Hong, J. H. J. Phys. Chem. 1983, 87, 163; Herbst, E. Chem. Soc. Rev. 2001, 30, 168.

Cyano-Containing Molecules in the ISM & Titan’s Atmosphere

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Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl. 1989, 28, 1279.Hopf, H.; Witulski, B Pure & Appl. Chem. 1993, 65, 47.

Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann. 1995, 613.

Interesting/Unexpected Experimental Results

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Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl. 1989, 28, 1279.Hopf, H.; Witulski, B Pure & Appl. Chem. 1993, 65, 47.

Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann. 1995, 613.

Proposed ReactionPathway

Relative energies (kcal/mol) computed using B3LYP/6-31G* level with ZPVE corrections

Not seen experimentally

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Guillemin, J. C.; Ferris, J. P. European Space Agency, [Special Publication], SP, 1992, ESA-SP-338 177.Woods, P. M.; Millar, T. J.; Zijlstra, A. A.; Herbst, E. Astrophys. J. 2002, 574, L167.

Photochemical Formation of Cyano-Benzenes

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Rotational Constants

(cm-1)Dipole Moment (D)

1.41295 55.94340.88410 18.8926 7.510.54380 14.1232

1.86607 42.35910.63019 25.2125 3.780.47110 16.3027

0.90219 27.04690.90219 27.0469 0.000.45109 13.5233

Computed at the B3LYP/6-31G* level

Computed Rotational Constants and Dipole Moments

Rotational Constants

(GHz)

Wohlfart, K.; Schnell, M.; Grabow, J.-U.; Kupper, J. J. Mol. Spectrosc. 2008, 247, 119.

7Isolation of Various Cyclobutadienes

IsolatedCram, 1991

IsolatedMasamune, 1977

IsolatedMaier, 1988

IsolatedGompper, 1968

Matrix IsolatedPeterson, 1997

Matrix IsolatedKrantz, 1973

“Self Destructive Molecule Lives Longer in Prison”

Image: Cram, D. J.; Cram, J. M. Container Molecules & Their Guests, Royal Soc. Of Chemistry: Great Britain, 1994, 209.Quote: Milgrom, L. J. Inclusion Phenom. Mol. Rcognit. Chem. 1992, 13, 97.

0.0 -9.4

-15.3 -14.5-15.3

-17.8 -18.4

n = 0 n = 1

n = 2

n = 3 n = 4

Relative energies (kcal/mol) computed using B3LYP/6-31G* level without ZPVE corrections

Maier, G.; Neudert, J.; Wolf, O.; Pappusch, D.; Sekiguchi, A.; Tanaka, M.; Matsuo, T. J. Am. Chem. Soc. 2002, 124, 13819.Balci, M.; McKee, M. L.; Schleyer, Paul von Rague J. Phys. Chem. A 2000, 104, 1246.

8Cyano-Substitution Effects on Cyclobutadiene

C4H4 + n CH3CN

C4H(4-n)(CN)n + n CH4

Order of Stabilization tBu < H < CN < SiH3 < Me < SiMe3

9Cyano-Substitution Effects on Cyclobutadiene Singlet-Triplet Gaps

aS-T Gap < 0 = singlet ground state. bCorrected for ZPV energies.

Singlet

Triplet

S-T gap

10Current/Future Studies

Krantz, A.; Lin, C. U.; Newton, M. D. J. Am. Chem. Soc. 1973, 95, 2744.Chapman, O. L.; De la Cruz, P.; Roth, R.; Pacansky, J. J. Am. Chem. Soc. 1973, 95, 1337.Bell,G. A.; Dunkin, I. R.; Shields, C. J. Spectrochin. Aceta, Part A, 1985, 41A, 1221.Webster, O. W. J. Am. Chem. Soc. 1966, 88, 4055.

• Robert J. McMahon• The McMahon Group– Nikki Burrmann– Katherine Traynor– Chris Shaffer– Laura Kopff– Brian Esselman– Alex Nolan– Matt Biller– Jeff Slosarxzyk– Dr. Caroline Pharr– Dr. Phillip Thomas

• NSF for funding

Acknowledgements

Lady Liberty on Lake Mendota, Lake Mendota, University of Wisconsin, Madison

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