99524-14-8Relevant articles and documents
Iminopropadienones, RN=C=C=C=O : Theory and Experiment
Mosandl, Thomas,Stadtmueller, Stefan,Wong, Ming Wah,Wentrup, Curt
, p. 1080 - 1086 (2007/10/02)
Ab initio molecular orbital calculations at the MP2/6-31G* level have been used to examine the structures and infrared spectra of a new class of compounds, the iminopropadienones, RN=C=C=C=O (R=H, CH3 and Ph).The agreement between calculated and experimental IR spectra of PhNCCCO,Ph(15)NCCCO, and PhNCC(13)CO is excellent.Inclusion of electron correlation is found to be important for the correct prediction of the relative intensities of the cumulenic stretching vibrations.As three iminopropadienones are predicted to have a slightly bent NCCCO backbone (CCC ca. 176 deg).As with carbon suboxide, these cumulenes are calculated to have an extremely flat CCC bending potential.The parent compound, HNCCCO (4a) is calculated to be thermodynamically stable toward dissociations into (i) HNCC + CO, (ii) HNC + CCO, (iii) HN + CCCO, and (iv) H. + NCCCO..Rearragement of 4a to the more stable cyanoketone isomer requires a sizeable barrier of 402 kJ mol-1 .The calculated stability of 4a is consistent with its experimental observation in neutralization-reionization mass spectrum.The adiabatic ionization energy and heat of formation of HNCCCO are predicted to be 9.51 eV and 175 kJ mol-1, respectively.
Cyclopentadienylideneethenone: Pyrolytic Generation and Argon Matrix Infrared Spectroscopic Study
Brown, Roger F. C.,Browne, Neil R.,Coulston, Karen J.,Eastwood, Frank W.,Irvine, Margaret J.,et al.
, p. 1321 - 1344 (2007/10/02)
Two previously reported pyrolytic precursors for cyclopentadienylideneethenone (4) and benzyne produced two strong infrared bands attributable to ketene type compounds when their pyrolysates were examined by argon matrix isolation spectroscopy.To determine which band should be assigned to (4), four new precursors for (4) and benzyne and two analogues labelled with 13C at the carbonyl group have been synthesized.Precursors (8) and (14) are respectively a caged system and a bridged system bearing a mixed anhydride with trifluoroacetic acid.Flash vacuum pyrolysis of (8) and (14) at 600-700 deg with trapping at 77 K gave pyrolysates which contaned biphenylene.Pyrolysis of (8) and (14) at 600-700 deg in a stream of argon followed by deposition as an argon matrix at about 10 K showed that both produced a pyrolysate absorbing at 2089 cm-1 assigned to (4).Precursors (24) and (25) and the previously reported (18) and (27) are Meldrum's acid derivatives designed to yield the hypothetical cyclopentadienylide Meldrum's acid (19) by cage fission or retro-Diels-Alder reaction.They all gave their biphenylene on flash vacuum pyrolysis at 600-700 deg and their pyrolysates in argon matrices showed absorption both at 2089 cm-1 due to (4) and at 2225 cm-1 due to an unidentified ketene.The frequency shift resulting from substitution of 13C in the carbonyl group (52 cm-1) is in accordance with the assignment of the 2089 cm-1 band to (4).The pyrolysates from precursors (8a), (14), (18a), (25) and (27) were allowed to react with methanol and the resulting mixtures were hydrogenated.In all cases methyl cyclopentylacetate was obtained.
