| Triplet E-vinylcarbene (HCCH=CH2) has been generated in a small amount from diazopropene as seen with IR and ESR (lambda > 534 nm, Ar, 10 K) (Chapter 1). Our attempts to obtain an UV-Vis spectrum of this molecule failed. Competing reactions at long wavelengths included formation of cyclopropene, allene, and 3H-pyrazole.; Propenylidene (CH3CH=C) was a surprising species that was also observed in our IR studies of C3H4 (Ar, 10 K) (Chapter 1). To further verify its identity and its role in the conversion of vinylcarbene to propyne, we synthesized a deuterium labeled precursor, 3-d 1-diazopropene. This study showed that vinylcarbene did not directly produce propyne though propenylidene did. Further studies are needed to help confirm propenylidene's detection by IR and to study another, unassigned species that also produced propyne.; Triplet dicyanocarbene (N≡C--C--C≡N) and its isomers were reexamined through matrix-isolation experiments and B3LYP/6-31G* calculations (Chapter 2). Triplet cyanoisocyanocarbene (N≡C--C--N=C) was the molecule most closely examined. The experimental IR of this molecule revealed only one strong absorption, at ∼1825 cm-1, though B3LYP/6-31G* calculations predicted two strong absorptions. An ESR spectrum of this molecule revealed a D value of 0.5967 cm-1 an E value of 0.002 cm -1. The low E value may indicate that triplet cyano-isocyanocarbene is more linear than predicted by B3LYP/6-31 G* calculations, though the molecule wobbling in the matrix is another possibility for this finding.; We also obtained IR evidence for triplet diazodicyanomethane (Chapter 2). The appearance of this set of IR absorptions corresponds to a visible purple color of the matrix, though whether the purple color is an emission or not has not been conclusively determined. UV-Vis absorptions also corresponded to the appearance of this species. The ESR spectrum also displayed signals, though we could not interpret these signals as they all appeared at a lower magnetic field than what would be expected for an organic triplet.; Finally, an attempt was made to synthesize cis-1-isocyano-but-1-ene-3-yne (Chapter 3). This molecule was predicted to undergo a Bergman cyclization, through a novel meta-diradical intermediate. However, a successful synthetic route was not found. |
