Y-aromaticity

In organic chemistry, the term Y-aromaticity is used to describe a Y-shaped, planar (flat) molecule with resonance bonds that exhibits more stability than other geometric or connective arrangements with the same set of atoms.

It is developed to explain the extraordinary stability of guanidinium cation and high basicity of the Guanidine. Guanidinium is not a ring molecule, and is cross-conjugated rather than a linear π system, but is reported to have its six π-electrons delocalized over the whole molecule. The concept is controversial and some authors emphasize different effects.^[1][2][3]

Trimethylenemethane Dication has extraordinary stability than the Butadienyl Dication.^[4]

See also

• Guanidine
• Aromaticity

References

1. ↑ Gobbi, Alberto; Frenking, Gemot (1993). "Y-Conjugated compounds: the equilibrium geometries and electronic structures of guanidine, guanidinium cation, urea, and 1,1-diaminoethylene". J. Am. Chem. Soc. 115: 2362–2372. doi:10.1021/ja00059a035. 
2. ↑ Wiberg, Kenneth B. (1990). "Resonance interactions in acyclic systems. 2. Y-Conjugated anions and cations". J. Am. Chem. Soc. 112: 4177–4182. doi:10.1021/ja00167a011. 
3. ↑ Caminiti, R.; Pieretti, A.; Bencivenni, L.; Ramondo, F.; Sanna, N. (1996). "Amidine N−C(N)−N Skeleton:  Its Structure in Isolated and Hydrogen-Bonded Guanidines from ab Initio Calculations". J. Phys. Chem. 100: 10928–10935. doi:10.1021/jp960311p. 
4. ↑ Dworkin, Amy; Naumann, Rachel; Seigfredi, Christopher; Karty, Joel M.; Mo, Yirong (2005). "Y-Aromaticity:  Why Is the Trimethylenemethane Dication More Stable than the Butadienyl Dication?". J. Org. Chem. 70: 7605–7616. doi:10.1021/jo0508090.