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Volumn 70, Issue 19, 2005, Pages 7744-7754

o-Phenylene halocarbenonitrenes and o-phenylene chlorocarbenocarbene: A combined experimental and computational approach

Author keywords

[No Author keywords available]

Indexed keywords

BUTADIENE; CARBON INORGANIC COMPOUNDS; COMPUTATIONAL METHODS; HALOGEN COMPOUNDS; RING OPENING POLYMERIZATION; SPECTROSCOPIC ANALYSIS; SUBSTITUTION REACTIONS;

EID: 24944531310     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo0512204     Document Type: Article
Times cited : (11)

References (58)
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    • Hund, F.1
  • 23
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    • note
    • The weakness of this π-bond is presumably due to the loss of the aromaticity of the benzene ring in the ground states.
  • 27
    • 24944536691 scopus 로고    scopus 로고
    • note
    • The best linear fit has a slope of 0.97 (1.00), an intercept of -4.4 kcal/mol (-3.0 kcal/mol), and a squared-regression coefficient of 0.9965 at the CASPT2 (MCSCF) level of theory.
  • 28
    • 24944492895 scopus 로고    scopus 로고
    • note
    • At the MCSCF level, the values are -0.90, 29.6 kcal/mol, and 0.9968, respectively.
  • 29
    • 0003053470 scopus 로고
    • This can be realized with a substituent that is a stronger π-donor than F, as for example with an amino or even perhaps with a hydroxy one. Feller, D.; Borden, W. T.; Davidson, E. R. Chem. Phys. Lett. 1980, 71, 22.
    • (1980) Chem. Phys. Lett. , vol.71 , pp. 22
    • Feller, D.1    Borden, W.T.2    Davidson, E.R.3
  • 30
    • 24944455871 scopus 로고    scopus 로고
    • note
    • -1 peak. Indeed, the ratio of the areas of the two peaks is about 1.4, which compares favorably to the 3:1 ratio of corresponding computed intensities.
  • 31
    • 24944476531 scopus 로고    scopus 로고
    • note
    • -1 are also predicted, these are very weak (7, 7, and 2 km/mol, respectively) and not likely to be observable under our experimental conditions.
  • 32
    • 24944490022 scopus 로고    scopus 로고
    • note
    • Apart from Z- and E-6-BrN the following aminocarbene and two cycloalkynes were screened computationally, but it is unlikely that they were formed.
  • 33
    • 24944554484 scopus 로고    scopus 로고
    • note
    • The UV/vis spectra also provide some evidence for this, since the band due to the initial photoproduct was notably weaker in the photolysis of 1-FN as opposed to that in photolysis of 1-ClN and 1-BrN.
  • 36
    • 24944489205 scopus 로고    scopus 로고
    • note
    • -1 (32 km/mol) for 4-FN, 4-ClN, and 4-BrN, respectively.
  • 37
    • 24944502239 scopus 로고    scopus 로고
    • note
    • The reported calculations refer to thermal reactions, which are unlikely to be taking place under our experimental conditions. It is more likely that the diradicals 2-XN are extremely photochemically reactive and once formed are rapidly converted to the observed products. Alternatively, excited states of the precursors 1-XN or intermediates resulting from the loss of one nitrogen molecule (e.g., nitrenediazirines) could give rise to the observed products by simultaneous loss of nitrogen. While these more likely processes may give product ratios that reflect the ground-state proclivities of the diradicals, this can neither be proved nor disproved by the current data.
  • 38
    • 24944523242 scopus 로고    scopus 로고
    • note
    • 1A′-2-ClN, E-6-ClN, Z-6-ClN these are: -0.26 (0.14), -0.32 (0.06), and 0.00 (0.43), respectively.
  • 41
    • 24944543894 scopus 로고    scopus 로고
    • note
    • The biradical is described by a spin-broken symmetry wave function while Z-6-XN is a closed-shell singlet. Attempts to locate the transition state were unsuccessful, as the calculation seemed to wander from the open-shell surface to the closed one. Apparently an MCSCF treatment is required, and it is quite possible that a conical intersection connects the two singlet surfaces. However, this also may not be enough since the vibrational mode connecting the two isomers may need to be taken into account at the same time. Whatever the case, this is beyond the scope of the current work.
  • 44
    • 24944448650 scopus 로고    scopus 로고
    • note
    • 31 This correlation is similar to that for 2-XN.
  • 45
    • 24944537036 scopus 로고    scopus 로고
    • note
    • The energy of the transition structure connecting E,E-2-ClC with 3-ClC is 0.1 kcal/mol higher than that of E,E-2-ClC, but it becomes lower (by 0.2 kcal/mol, Figure 5a) when ZPE corrections are included. Thus, this barrier is small (if it exists at all) and is in agreement with the MCSCF result of "spontaneous" ring closing to 3-ClC.
  • 46
    • 24944464979 scopus 로고    scopus 로고
    • note
    • Ignoring the small energy differences between the four isomers and assuming that all are formed in equal amounts, the data in Figure 5 suggest that more than 25% of the (3-ClC and 4-ClC) mixture should be 4-ClC.
  • 47
    • 24944433069 scopus 로고    scopus 로고
    • note
    • For reasons analogous to the ones mentioned in ref 30, attempts to locate a transition structure for the Z,E-2-ClC to Z-6-ClC isomerization were unsuccessful.
  • 49
    • 4243661307 scopus 로고
    • -1 area can be attributed to weak hot bands of acetylenic compounds (Klaboe, P.; Klosterjensen, E.; Bjarnov, E.; Christensen, D. H.; Nielsen, O. F. Spectrochim. Acta 1975, 31A, 931), thus making doubtful the observation of 4-ClC. However, this would only increase the observed [3-ClC]/[4-ClC] ratio, strengthening the argument presented in the next section.
    • (1975) Spectrochim. Acta , vol.31 A , pp. 931
    • Klaboe, P.1    Klosterjensen, E.2    Bjarnov, E.3    Christensen, D.H.4    Nielsen, O.F.5
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    • Gaussian Inc.: Pittsburgh, PA
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.