Sonia Antolínez

Axial and Equatorial Hydrogen Bonds in the Tetrahydropyran⋅⋅⋅HCl Dimer

Two hydrogen-bond complexes formed between tetrahydropyran and hydrogen chloride have been observed by using a molecular beam Fourier transform microwave spectrometer. The rotation constants are consistent with Cs symmetry, with HCl pointing to the domain of the axial and equatorial lone pair at the oxygen atom (shown on the left and right, respectively). The axial form has been found to be the more stable one.

Jet-cooled rotational spectrum of laser-ablated 1,3,5-trithiane ☆

Abstract The jet-cooled rotational spectra of the parent and three isotopic species (13CC2H6S3, C3H634SS2 and C3H633SS2) in natural abundance of 1,3,5-trithiane have been observed by laser ablation combined with molecular-beam Fourier transform microwave spectroscopy. The r0 and rs structures of the molecule have been determined from the rotational data. The sensitivity of the experimental set-up proved to be high enough to observe the 33S isotopomer in natural abundance. An analysis of the nuclear quadrupole hyperfine structure due to the 33S nucleus allowed the determination of the quadrupole coupling tensor, giving some insight about the electronic distribution around this atom.

The axial and equatorial hydrogen bonds in the tetrahydropyran...HF complex

Characterized by microwave spectroscopy after their formation in a supersonic jet, the axial and equatorial hydrogen bond conformers of the title complex were studied. The axial form--shown in the picture--has been found to be the most stable one. The experimental data are consistent with a C(s) symmetry for both conformers, in which linear hydrogen bonds lying in the symmetry plane bisect the C-O-C angle. The structure of tetrahydropyran subunit in the axial form was also determined and no significant structural distortion occurs upon complexation.

AXIALE UND AQUATORIALE WASSERSTOFFBRUCKENBINDUNGEN IM TETRAHYDROPYRAN... HCL-DIMER

Die Wasserstoffbruckenkomplexe, die von Tetrahydropyran und Chlorwasserstoff gebildet werden, wurden mit einem Puls-Fourier-Transform-Mikrowellenspektrometer am Molekularstrahl detektiert und analysiert. Die Rotationskonstanten sind im Einklang mit der Cs-Symmetrie der Komplexe, wobei das HCl-Molekul zum axialen oder zum aquatorialen freien Elektronenpaar am O-Atom ausgerichtet ist (links bzw. rechts gezeigt). Die axiale Form erwies sich als die stabilere.

Rotational spectra and structure of the hydrogen-bonded complex oxetane⋯HCl

Abstract The hydrogen-bonded complex oxetane⋯HCl generated in a supersonic jet has been characterised by Fourier transform microwave spectroscopy. For the observed conformer the spectra of the four isotopic species C 3 H 6 O⋯H 35 Cl,C 3 H 6 O⋯H 37 Cl,C 3 H 6 O⋯D 35 Cl and C 3 H 6 O⋯D 37 Cl have been measured. Rotational data are consistent with a C s symmetry for the complex, with HCl lying in the symmetry plane bisector to the COC angle. The planar configuration of isolated oxetane has been reasonably elucidated to remain in the dimer, which implies that no significant change in the potential energy function of ring puckering motion of oxetane occurs upon complexation.

The microwave spectrum, ab initio analysis, and structure of the fluorobenzene–hydrogen chloride complex

The fluorobenzene–hydrogen chloride π-hydrogen-bonded complex has been studied by high resolution microwave spectroscopy and ab initio calculations. Rotational spectra of the C6H5F–H35Cl, C6H5F–H37Cl, and C6D5F–H35Cl isotopomers were assigned using pulsed molecular beam techniques in a Fourier-transform microwave spectrometer. The spectra are consistent with a structure of the complex in which the HCl is above the fluorobenzene ring near the ring center, similar to the benzene–HCl prototype dimer. An analysis of the inertial data and the chlorine quadrupole coupling tensor results in two mathematically possible locations for the HCl subunit with respect to the fluorobenzene arising from sign ambiguities in interpreting the spectral constants. One structure has the HCl nearly perpendicular to the aromatic ring; the other has the HCl pointing toward the fluorine end of the ring. Spectral intensities for the μa and μb transitions favor the former configuration. Ab initio calculations (MP2/6-311++G(2df,2pd)+B...

Jet-cooled rotational spectra and structure of the cyclobutanone⋯hydrogen chloride complex

Abstract The rotational spectra of three isotopic species C 4 H 6 O⋯H 35 Cl, C 4 H 6 O⋯H 37 Cl and C 4 H 6 O⋯D 35 Cl of the hydrogen-bonded dimer formed by cyclobutanone and hydrogen chloride have been studied by means of microwave spectroscopy in a supersonic jet. Rotational constants, centrifugal distortion constants and Cl-nuclear quadrupole coupling parameters have been determined for the ground state and for a vibrationally excited state attributable to the ring-puckering motion of the cyclobutanone subunit. The spectroscopic constants have been interpreted in terms of a C s symmetry in which the monomers are coplanar with: r (O⋯H)=1.88(3) A, ∠(CO⋯H)=112.3(7)° and a deviation θ of the O⋯H–Cl nuclei from collinearity of 13.1(6)°.

Conformation and Stability of the Hydrogen-Bonded Complex 6-Oxabicyclo[3.1.0]hexane⋅⋅⋅HCl

The hydrogen-bonded complex between 6-oxabicyclo[3.1.0]hexane and hydrogen chloride was investigated by microwave spectroscopy in a supersonic jet. A dual flow pulsed valve was used to preclude chemical reaction between the monomers. Only the equatorial conformer was observed and the spectra of three isotopomers, (C5H8O, H35Cl), (C5H8O, H37Cl) and (C5H8O, D35Cl), were measured. The derived structure of the complex has Cs symmetry with the hydrogen chloride pointing to the domain of the equatorial lone pair of electrons at the oxygen atom. The three atoms involved in the hydrogen bond adopt a bent arrangement with a O...H distance of 1.77(4) A, a (O...H-Cl) angle of 115(4)degrees, and a deviation of 15.4(14)degrees of the hydrogen bond from collinearity. In agreement with the experimental results, ab initio calculations predict the equatorial form to be the most stable one.

The microwave spectra and structure of the complex 7-oxabicyclo[2.2.1]heptane...HF

The hydrogen-bonded complex formed between 7-oxabicyclo[2.2.1]heptane and HF (OBH···HF) has been generated in a supersonic jet and characterised by Fourier transform microwave spectroscopy. The rotational transitions of the parent and C6H10O···DF species, together with the spectra corresponding to 13C monosubstituted species have been analysed. Spectral analysis yielded rotational and centrifugal distortion constants and the parameter Daa accounting for HF subunit spin (H)–spin (F) coupling. These data are consistent with Cs symmetry and a linear hydrogen bond lying in the symmetry plane bisector to the angle COC. The structure of the OBH subunit in the complex has been determined and it can be concluded that no significant structural distortion occurs upon complexation. No detectable inversion doubling attributed to the HF inversion has been observed.

Rotational spectra, electric dipole moment and methyl group internal rotation barrier of 1,1,1-trifluoropropane

The microwave spectra of the main species of 1,1,1-trifluoropropane and the three singly substituted 13 C isotopic species have been studied in the frequency region 6–40 GHz using Stark modulation and Fourier-transform microwave spectroscopy. Accurate rotational spectroscopic constants and quartic centrifugal distortion constants have been obtained for the ground vibrational state. A reasonable molecular structure has been derived from the rotational constants and planar moments of inertia. The barrier to internal rotation of the methyl top has been determined from the A–E splittings to be 2635(4) cal mol 11 . The dipole moment components have been computed from Stark effect measurements to be µ a = 2.172(4) D and µ b = 1.140(9) D with a total dipole moment of µ = 2.453(8) D.