Guanidine, trimethylenemethane, and "Y-delocalization." Can acyclic compounds have "aromatic" stability?

Gund, Peter

doi:10.1021/ed049p100

Cited by 211 publications

(99 citation statements)

References 7 publications

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“…The relative stability is in agreement with the experimental observation [16,17]. The special stability of the cross conjugate systems has been noted as the Y-delocalization [18].…”

Section: Polarization Of Bondssupporting

confidence: 88%

An Orbital Phase Theory

Inagaki

2009

Orbitals in Chemistry

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Cyclic orbital interactions are contained in non-cyclic conjugation as well as cyclic conjugation. For effective interactions, the orbitals are required to meet simultaneously the phase continuity conditions: (1) out of phase relation between electron-donating orbitals; (2) in phase relation between electron-accepting orbitals and between electron-donating and -accepting orbitals. The orbital phase theory is applicable to diverse chemical phenomena of non-cyclic conjugate systems, e.g., relative stabilities of non-cyclic isomers, and selectivities of the reactions through non-cyclic transition structures. The orbital phase theory also includes the rules for cyclic systems, i.e., the Wooward-Hoffmann rule for stereoselection of organic reactions and the Hueckel 4n + 2p electron rule for aromatic molecules. Derivation and applications of the orbital phase theory are reviewed.

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“…The relative stability is in agreement with the experimental observation [16,17]. The special stability of the cross conjugate systems has been noted as the Y-delocalization [18].…”

Section: Polarization Of Bondssupporting

confidence: 88%

An Orbital Phase Theory

Inagaki

2009

Orbitals in Chemistry

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“…. 99 (i.e. six electrons in the four-orbital system derived from the two carbon and two fluorine p orbitals).…”

Section: Discussionmentioning

confidence: 99%

Density functional calculations of the influence of substitution on singlet–triplet gaps in carbenes and vinylidenes

Worthington¹,

Cramer²

1997

J. Phys. Org. Chem.

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Density functional theory calculations of multiplet splittings are presented that agree closely with experimental measurements for six carbenes and six vinylidenes. The calculations are further analyzed to gauge the relative importance of different factors influencing the stabilities of the different spin and electronic states. In the carbene series, with halogen substituents, orbital rehybridization effects and charge redistribution effects are large. The magnitude of -conjugation (back-bonding) is calculated to be only moderately larger (6-8 kcal mol ؊ 1 ) for singlets than for triplets based on natural bond orbital-derived conjugation energies. In the vinylidene series, substituion effects are primarily associated with through-space and through-bond inductive stabilization effects, especially hyperconjugation; -conjugation effects are found to be small

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“…Basic properties of guanidines have been used for catalysis of various organic reactions [62]. The unusual thermodynamic stability of acyclic guanidines and their monoprotonated forms is ascribed to the following factors: resonance stabilization; Y-aromaticity [63,64]; favourable distribution of positive charge that leads to a favorable Coulomb interaction; aromaticity; stabilization by intramolecular hydrogen bonding; and the effect of solvation on the stability of the protonated form (strong hydrogen bond between the cation and solvent molecules in solution). All of these factors play an important role in the gas phase and in solution [65].…”

Section: Guanidinesmentioning

confidence: 99%