title: Structures and intriguing conformational behavior of 1- and 2-naphthalenesulfonamides as determined by gas-phase electron diffraction and computational methods.
abstract: The saturated vapors of 1- and 2-naphthalenesulfonamides (1-NaphSA and 2-NaphSA) were studied by the gas-phase electron diffraction/mass-spectrometric method at 413(9) and 431(9) K. According to quantum chemical calculations (DFT/B3LYP and MP2 with cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis set) 1-NaphSA possesses four conformers with different orientations of the SO2NH2 fragment relative to the naphthalene frame and eclipsed or staggered orientation of the N-H and S═O bonds, whereas 2-NaphSA possesses only two conformers with different orientations of the N-H and S═O bonds. It was experimentally established that vapors over 1-NaphSA and 2-NaphSA exist predominantly (up to 75 mol %) of low-energy conformers of C1 symmetry in which the C-S-N planes deviate from perpendicular orientation relative to the naphthalene skeleton with near eclipsed orientation of the N-H and S═O bonds of the SO2NH2 fragment. The following geometrical parameters (Å and degrees) of the dominant conformers were derived: r(h1)(C-H) = 1.089(4), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.761(10), r(h1)(S-O)av = 1.425(3), r(h1)(S-N) = 1.666(10), ∠C-C1-C = 119.8(2), ∠C1-S-N = 104.5(22), C9-C1-S-N = 69.5(30) for 1-NaphSA; r(h1)(C-H) = 1.083(5), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.780(7), r(h1)(S-O)av = 1.427(4), r(h1)(S-N) = 1.668(6), ∠C-C2-C = 123.0(3), ∠C2-S-N = 103.6(19), C1-C2-S-N = 110(10) for 2-NaphSA. The connection between nonequivalence of the C-C bonds in the naphthalene frame and spatial orientation of the substituents SO2NH2 is discussed. Transition states between conformers and enantiomers were determined.
authors.affiliation: Ivanovo State University , Ivanovo 153025, Russia.
authors.forename: Nina I
authors.initials: NI
authors.lastname: Giricheva
authors.forename: Vjacheslav M
authors.initials: VM
authors.lastname: Petrov
authors.forename: Marwan
authors.initials: M
authors.lastname: Dakkouri
authors.forename: Heinz
authors.initials: H
authors.lastname: Oberhammer
authors.forename: Valentina N
authors.initials: VN
authors.lastname: Petrova
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Shlykov
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Ivanov
authors.forename: Georgiy V
authors.initials: GV
authors.lastname: Girichev
mesh_terms: D004583:Electrons; D005740:Gases / Q000737:chemistry; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D011789:Quantum Theory; D013449:Sulfonamides / Q000737:chemistry*
chemical_list: D005740:Gases; D009281:Naphthalenes; D013449:Sulfonamides