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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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