Geometric isomers of vinylmethylene

Hutton, R. S.; Manion, Marcia L.; Roth, Heinz D.; Wasserman, E.

doi:10.1021/ja00821a058

Cited by 48 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the planar vinylmethylene, 2, four states are again possible: a singlet and triplet corresponding to 2a and two singlets 2b (designated 2n (6) or 02 (9)) and 2c (4n or p2). Both calculations and esr results (13,14) give triplet 2a as the most stable state. Singlet 2a correlates with l a and is the likely first-formed intermediate in the thermal reactions of cyclopropenes (10).…”

Section: Introductionmentioning

confidence: 82%

The thermal chemistry of vinyldiazo compounds as a method for the generation of vinylmethylenes

Pincock¹,

Murray²

1979

Can. J. Chem.

View full text Add to dashboard Cite

. Can. J. Chem. 57,1403Chem. 57, (1979. The thermal chemistry of a series of substituted 1-aryl-3-methyl-2-phenyl-1-diazobut-2-enes has been examined. These vinyldiazo compounds react in two parallel pathways: cyclization to a 3-aryl-5,5-dimethyl-4-phenyl-5H-pyrazole or loss of nitrogen and cyclization to a l-aryl-2-phenyl-3,3-dimethylcyclopropene presumably by a vinylmethylene intermediate. The kinetics of these processes reveal quite different substituent effects. The relation of these results to the stability of the vinylmethylene produced and to the singlet photochemistry of cyclopropene derivatives is discussed. JAMES A. PINCOCK et KIM P. MURRAY. Can. J. Chem. 57,1403Chem. 57, (1979. On a ktudie la thermochimie d'une skrie d'aryl-1 mkthyl-3 phenyl-2 diazo-1 butbnes-2 substituks. Ces composks vinyldiazo rkagissent par deux voies paralltles: une cyclisation conduisant a l'aryl-3 dimkthyl-5,5 phknyl-4 5H-pyrazole ou une perte d'azote et une cyclisation en aryl-1 phknyl-2 dimkthyl-3,3 cycloproptne probablement par un intermkdiaire vinylmkthylbne. Des ktudes cinetiques de ces processus rkvtlent des effets de substituants importants. On discute de la relation qui existe entre ces rksultats et la stabilite du vinylmkthylene qui est produit ainsi que la photochimie singulet des dkrivks du cycloproptne.[Traduit par le journal] IntroductionHowever, recent results for cases with unsymmetrical The photochemical reactivity of the singlet excited substitution on the double bond (1, 2, 4, 5) have state of cyclopropene derivatives has generally been led to considerable speculation as to the effect of explained in terms of o bond cleavage and the these substituents on ring cleavage. Some examples chemistry of the vinyl methylenes formed (1-3). are summarized in reactions [I] to [4].

show abstract

Section: Introductionmentioning

confidence: 82%

The thermal chemistry of vinyldiazo compounds as a method for the generation of vinylmethylenes

Pincock¹,

Murray²

1979

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Hutton et a1. (18) have arrived at the same description of this molecule on the basis of its esr sDectrum.…”

Section: Atomic Properties and Ground State Multiplicitiesmentioning

confidence: 94%

Atomic properties and the reactivity of carbenes

MacDougall¹,

Bader²

1986

Can. J. Chem.

View full text Add to dashboard Cite

The properties of the atoms in a number of substituted carbenes and silylene provide an understanding of the relative stabilities of their lowest lying singlet and triplet states and of their differing chemical reactivities. The theory of atoms in molecules defines all of an atom's properties, including its energy. In this research one finds that the methylenic carbon or silicon atom is energetically most stable in the triplet state of each system, while the ligands are most stable in the corresponding singlet state. It is also found that the average electron populations of the carbon and silicon atoms are largest in the triplet states. In systems where the carbon or silicon atom bears a net positive charge, as found in CHNH2, CF2, and SiH2, the excess in the transfer of charge to the more electronegative ligands in the singlet states stabilizes the ligands more than it destabilizes the central atom. These systems have singlet ground states. The relative susceptibility of singlet and triplet carbenes to electrophilic and nucleophilic attack is determined by the properties of the Laplacian of the charge distribution. This quantity assimilates the model of localized electrons in terms of local concentrations of electronic charge. It also determines regions from which electronic charge is locally depleted. These regions are found to coincide with those where the lowest-lying vacant orbital is concentrated.

show abstract

“…The enthalpies of the S 0 forms are 2.5 (syn) and 3.6 kcal mol À1 (anti) higher than the corresponding T forms of 14. Results of ESR experiments as well as ab initio calculations carried out for vinylmethylene [115][116][117] suggest that this carbene possesses a T ground state and a S-T splitting of less than 1 kcal mol À1 . Allenylcarbene 14 should not differ so strongly from vinylmethylene and, therefore, our results can be considered to be in line with experiment and other theoretical investigations.…”

Section: (D) Allenylcarbene 14mentioning

confidence: 95%

Exploration of the potential energy surface of C4H4 for rearrangement and decomposition reactions of vinylacetylene: A computational study. Part I

Cremer

Kraka

Joo

et al. 2006

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The potential energy surface (PES) of C4H4 was explored using quantum chemical methods (DFT, MP2, MP4, GVB-MP2, CCSD(T), G2M, CBSQ/APNO) and 43 different structures located at global and local minima were identified. The majority of these structures correspond to carbenes, a minority to closed shell systems and biradicals (carbyne structures were not investigated). Whereas the chemistry of the closed shell systems such as vinylacetylene (1), butatriene (2), methylenecyclopropene (3), cyclobutadiene (5) or tetrahedrane (15) is well known, the carbenes represent unusual structural entities. 2-Methyl-cycloprop-2-en-1-ylidene (4) (DeltaDeltaH(298) = 36.2 kcal mol(-1) relative to 1) in its sigma2pi0 electron configuration at the carbene C of the 1A ground state is of comparable stability to cyclobutadiene (5) (DeltaDeltaH(298) = 33.4 kcal mol(-1); exp. value: 32.1 kcal mol(-1) as a result of aromatic 2pi-delocalization; carbene 3-vinylidenecyclopropene (13) (DeltaDeltaH(298) = 53.9 kcal mol(-1) does not possess C(2v) symmetry but has the vinylidene group bent toward the three-membered ring (C(s)-symmetry) thus representing a frozen path point of the chelotropic addition of :C=C: to ethene. Allenyl carbene (14) has a triplet ground state and two low lying excited singlet states of closed shell (2.5 kcal mol(-1) higher) and open shell character (14.1 kcal mol(-1)). Carbene 14 is a crossing point on the C4H4 PES connecting closed-shell systems with each other. Because of the stability of 1, its rearrangement reactions are all connected with high activation enthalpies requiring 66 up to 92 kcal mol(-1) so that they energetically overlap with the activation enthalpies typical of decomposition reactions (from 90 kcal mol(-1) upward). The possible rearrangement reactions of 1 are investigated with a view to their relevance for the chemical behavior of the molecule under the conditions of Titan's atmosphere.

show abstract

Geometric isomers of vinylmethylene

Cited by 48 publications

References 0 publications

The thermal chemistry of vinyldiazo compounds as a method for the generation of vinylmethylenes

The thermal chemistry of vinyldiazo compounds as a method for the generation of vinylmethylenes

Atomic properties and the reactivity of carbenes

Exploration of the potential energy surface of C4H4 for rearrangement and decomposition reactions of vinylacetylene: A computational study. Part I

Contact Info

Product

Resources

About