Substituted Ortho-Benzynes: Properties of the Triple Bond

Abstract

Ortho-benzyne has been well studied by both experiment and theory. Its substituted variants, however, have been less carefully examined. Benchmark data are computed for unsubstituted ortho-benzyne using several density functional theory functionals and basis sets, up to cc-pVQZ. Optimized geometries for the substituted ortho-benzyne as well as harmonic vibrational frequencies and singlet–triplet splittings are computed using the benchmarked functionals. A proximal (syn)­OH substitution causes a mean θ1 distortion of +8.1 ± 1.4° from ortho-benzyne. Substituting in the proximal position with F shifts the singlet–triplet splitting by +4.5 ± 0.4 kcal mol–1 from ortho-benzyne. Natural bond orbital analysis, including natural Coulomb electrostatics, elucidates the presence of three influences from the selected substituents: hyperconjugative, resonance, and electrostatic effects.

o-Silylaryl Triflates: A Journey of Kobayashi Aryne Precursors

“…Recently, Mirzaei and Khosravi employed frontier molecular orbital contribution analysis and orbital electronegativity to predict the aryne regioselectivity. More theoretical studies on the structure of substituted benzynes were reported by Schaefer et al…”

“…Recently, Mirzaei and Khosravi employed frontier molecular orbital contribution analysis 160 and orbital electronegativity 161 to predict the aryne regioselectivity. More theoretical studies on the structure of substituted benzynes were reported by Schaefer et al 162 Figure 4 lists the geometry optimized structures of some commonly substituted benzynes, 1 3 0 , 1 4 3 , 1 4 6 hetarynes, 145,149,152,153 cyclohexynes, 153−155 and 1,2-cyclohexadienes 156,157 using DFT methods. Based on the aryne Scheme 10.…”

Uncovering the hidden reactivity of benzyne/aryne precursors utilized under milder condition: Bonding and stability studies by EDA‐NOCV analyses

“…Stoermer and Kahlert 1 first generated the reactive aryne intermediate of benzofuran in 1902 and Wittig 2–4 proposed the zwitterionic nature of benzyne intermediate species, which was confirmed by Roberts 5,6 . Benzynes are electron deficient singlet intermediate species with a strained C≡C triple bond due to the inefficient overlap of orbitals with two electrons on two adjacent C‐atoms 7–14 . The experimental data of the benzyne show that the singlet‐triplet energy gap is nearly 37 kcal mol −1 14a .…”

“…5,6 Benzynes are electron deficient singlet intermediate species with a strained C≡C triple bond due to the inefficient overlap of orbitals with two electrons on two adjacent C-atoms. [7][8][9][10][11][12][13][14] The experimental data of the benzyne show that the singlet-triplet energy gap is nearly 37 kcal mol À1 . 14a The C≡C bond distance has been determined to be 1.24 Å.…”

“…Isosurface values are 0.003 au for Δρ (1)-(2) . The eigenvalues jν n j give the size of the charge migration in e. the direction of the charge flow of the deformation densities is red!blue.F I G U R E 7 The shape of the deformation densities Δρ (1)-(2) that correspond to ΔE orb(1)-(2) , and the associated MOs of ArCO 2 N 2(8) and the fragments orbitals of ArCO 2 and N 2 in the singlet state at the BP86-D3(BJ)/TZ2P level. Isosurface values are 0.003 au for Δρ (1)-(2) .…”