Rosa M. Villamañán

The centimeter and millimeter microwave spectra of butadiene sulfone and α,α′-D4 butadiene sulfone

Abstract Microwave measurements on the ground and first eight excited states of the ring-puckering vibration of butadiene sulfone have been extended to millimeter wavelengths. The microwave spectra of the same vibrational states of α,α′-D 4 butadiene sulfone have been observed. For both isotopomers the Coriolis interaction between the v = 0 and v = 1 states has been analyzed to give the energy separation between these two states. These data and the variation of the rotational constants have been used to derive reduced potential functions for the ring-puckering vibration. The barrier to ring inversion is 49(2) cm −1 for butadiene sulfone and 44(2) cm −1 for the α,α′-D 4 isotopomer. The ring-puckering vibrational dependence of the quartic centrifugal distortion constants, including a small dependence of Δ J and δ J , has been accounted for.

Microwave spectrum and rotational isomerism of 3-fluorostyrene

Abstract Microwave spectra of 3-fluorostyrene are analyzed in the frequency region 26.5–40.0 GHz. The analysis confirms the existence in the gas phase of two rotational isomers, cis and trans. Relative intensity measurements and estimated electric dipole moment components give an energy difference of 26±46 cm−1 with the cis rotamer being the more stable. Several torsional excited states are assigned for each form. The inertia defect and the variation of the rotational constants with torsional quantum number demonstrate that the equilibrium conformation is planar for both rotamers. Plausible structures for each rotamer are proposed from the rotational constants. For the cis rotamer, a single-minimum potential function of the quadratic-quartic type is estimated for the bottom of the torsion potential energy curve of the vinyl group.

Rotational spectrum and ring-puckering vibration in 2,5-dihydrofuran

Abstract The rotational spectrum of 2,5-dihydrofuran has been analyzed in the frequency region of 26.5–40.0 GHz. From the ground state inertial defect and the variation of the rotational parameters with the ring-pucking quantum number, a strictly planar ring equilibrium configuration has been established. A single-minimum one-dimensional potential function of the quadratic-quartic type has been estimated for the ring-puckering vibration. From the Stark shifts, the electric dipole moment in the ground and several excited states has been obtained.

Ring-puckering potential function for butadiene sulphone

The ring puckering in butadiene sulphone has been investigated using microwave spectroscopy and ab initio computations. Microwave spectra of the ground and first eight excited states of the ring‐puckering vibration have been observed. A two state analysis of the vibration–rotation interaction for the v=0 and v=1 states gives an energy separation between these states of 4.97 (3) cm−1. This separation and the vibrational dependence of the rotational constants have been used to derive the reduced potential function V(X)=4.7(X4−6.5X2) for the ring‐puckering vibration. This potential function gives a barrier to ring inversion of 50 (11) cm−1 and an equilibrium dihedral angle of ≊20°. Ab initio computations using STO 3‐21G* orbitals and full geometry optimization give a barrier height of 88 cm−1 and an equilibrium dihedral angle of 19.2°. The ab initio computations predict structural relaxation including a rocking of the sulphone group during the ring‐puckering motion. This is supported by calculations of the v...

A study of low-frequency skeletal ring modes in pentamethylene oxide and pentamethylene sulfide by microwave spectroscopy

Abstract The microwave spectra of pentamethylene oxide and pentamethylene sulfide have been studied in the frequency range 18.0–40.0 GHz. Spectra of the ground state and several satellite excited states have been assigned for both molecules. From the energy differences obtained by relative intensity measurements and their comparison with those reported from vibrational analysis, these excited states have been assigned to the low-frequency skeletal ring modes.

Rotational isomerism in monofluorobenzaldehydes

Microwave spectra of 2- and 3-fluorobenzaldehydes have been investigated in the frequency region 26.5–40.0 GHz. Only the O-trans form of 2-fluorobenzaldehyde was detected in the gas phase. Analysis of 3-fluorobenzaldehyde confirmed the existence of two rotational isomers: O-cis and O-trans. From relative intensity measurements the O-cis form was shown to be more stable than the O-trans form by 300 ± 200 cal mol–1. The inertia defect values and the variation of the rotational constants with the torsional quantum number demonstrate that the equilibrium geometry is planar for all rotamers. Molecular structures which are in very good agreement with experimental rotational constants have also been derived.

Microwave spectrum of 4-fluorobenzaldehyde

Abstract The rotational spectrum of 4-fluorobenzaldehyde has been investigated in the 26.5–40.0 GHz frequency region. R -branch and Q -branch transitions allowed by μ a and μ b dipole moment components are assigned. Rotational parameters for the ground and several excited torsional states are derived which prove the molecule to be planar. Relative intensity measurements show that the first torsional state is about 107 ± 20 cm −1 above the ground state. This value is in good agreement with the far-IR data. Other vibrational satellites are also identified and a tentative assignemnt is proposed on the basis of the variation of the inertia defect.

The rotational spectrum of 2-methylcyclopentanone

Abstract The rotational spectra of 2-methylcyclopentanone in the ground and six vibrationally excited states have been observed in the frequency region from 26.5 to 40.0 GHz. The obtained rotational parameters are consistent with a twisted ring conformation in which the methyl group is in the equatorial position. On the basis of the vibrational assignment a lower limit for the internal rotation barrier of 3.5 kcal/mol has been calculated.

Conformation and internal rotation in 2-nitrofuran and 2-nitrothiophene by microwave spectroscopy

Abstract Results of a microwave investigation of the molecules 2-nitrofuran and 2-nitrothiophene are reported. Transitions in the ground state, torsional excited states and out-of-plane and in-plane excited states of the bending vibration of the nitro group have been assigned. The rotational parameters are consistent with a planar equilibrium configuration for both molecules. The torsional frequency has been derived from relative intensity measurements and inertial defect values. The barrier hindering internal rotation has been calculated to be 17kJ mol−1 and 19kJ mol−1 for 2-nitrofuran and 2-introthiophene, respectively.

EDUCACIÓN CIENTÍFICA CON ENFOQUE CIENCIA-TECNOLOGÍA-SOCIEDAD-AMBIENTE: CONSTRUCCIÓN DE UN INSTRUMENTO DE ANÁLISIS DE LAS DIRECTRICES CURRICULARES

The main objective of the Environment, Science, Technology and Society approach (ESTS) in science education is to develop scientific literacy in students, preparing them for the exercise of active and conscious citizenship. This view of education must be considered in curriculum guidelines and other documents governing the educational activity. An analytical tool to determine if the ESTS perspective is integrated into the curriculum documents has been developed. Its construction has been done in five stages on the basis of data and considerations of recent research in science education, as well as various tools already used in the ESTS perspective. This instrument has been publicly presented, debated and reformulated according to the suggestions received, and has been validated by experts. It is concluded that the proposal represents an effective tool to achieve the established objectives.