Microwave spectrum, structure, dipole moment, and quadrupole coupling constants of isopropylamine

Mehrotra, S. C.; Griffin, Lawrence L.; Britt, Chester O.; Boggs, James E.

doi:10.1016/0022-2852(77)90264-8

Cited by 21 publications

(11 citation statements)

References 16 publications

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“…The molecular structure for isopropylamine (C s , or trans) has been determined by the MW method, 58 but the experimental geometric values contain large uncertainties. More important is the fit of the MM4 structure to the experimental moments of inertia (later), which is very good.…”

Section: Isopropylaminementioning

confidence: 99%

Molecular mechanics (MM4) study of amines

et al. 2007

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The MM4 force field has been extended to include aliphatic amines. About 20 amines have been examined to obtain a set of useful molecular mechanics parameters for this class. The vibrational spectra of seven amines (172 frequencies) calculated by MM4 have an overall rms error of 27 cm(-1), compared with corresponding MM4 value of 24 cm(-1) for alkanes. The rms and signed average errors of the moments of inertia of nine simple amines compared with the experimental data were 0.18% and -0.004%, respectively. The heats of formation of 30 amines were also studied. The MM4 weighted standard deviation is 0.41 kcal/mol, compared with experiment. Electronegativity effects occur in the hydrocarbon portion of an amine from the nitrogen, and are accounted for by including electronegativity induced changes in bond lengths and angles, and induced dipole-dipole interactions in the molecule. Negative hyperconjugation results from the presence of the lone pair of electrons on nitrogen, and leads to the Bohlmann bands in the infrared, and also to strong and unusual geometric changes in the molecules (Bohlmann effect), all of which are fairly well accounted for. The conformational energies in amines appear to be less straightforward than those for most other classes of molecules, apparently because of the Bohlmann effect, and these are probably not yet completely understood. In general, the agreement between the MM4 calculated results and the available data is reasonably good.

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Section: Isopropylaminementioning

confidence: 99%

Molecular mechanics (MM4) study of amines

et al. 2007

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“… 36 , 37 Conversely, the rotational spectrum of IPA has been only observed for the most stable trans conformer. 38 , 39 In the present work, the laboratory investigation of the rotational spectrum of T -IPA has been extended. We have also attempted to detect rotational features of G -IPA, but our observations could not be interpreted unambiguously.…”

Section: Methodsmentioning

confidence: 99%

“…The trans isomer is a nearly oblate asymmetric-top rotor ( k = 0.81) belonging to the C s point group. It possesses a permanent electric dipole moment μ = 1.19(3)D, 38 lying almost completely on the c axis (μ c = 1.19 ± 0.03 D and μ b = 0.10 ± 0.04 D); μ a is zero by symmetry. Therefore, the pure rotational spectrum of T -IPA is dominated by c -type transitions (see Figure 1 ), whereas b -type ones are expected to be ∼150-times weaker.…”

Section: Methodsmentioning

confidence: 99%

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Rich Collection of n-Propylamine and Isopropylamine Conformers: Rotational Fingerprints and State-of-the-Art Quantum Chemical Investigation

et al. 2020

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The conformational isomerism of isopropylamine and n-propylamine has been investigated by means of an integrated strategy combining high-level quantum-chemical calculations and high-resolution rotational spectroscopy. The equilibrium structures (and thus equilibrium rotational constants) as well as relative energies of all conformers have been computed using the so-called “cheap” composite scheme, which combines the coupled-cluster methodology with second-order Møller–Plesset perturbation theory for extrapolation to the complete basis set. Methods rooted in the density functional theory have been instead employed for computing spectroscopic parameters and for accounting for vibrational effects. Guided by quantum-chemical predictions, the rotational spectra of isopropylamine and n-propylamine have been investigated between 2 and 400 GHz with Fourier transform microwave and frequency-modulation millimeter/submillimeter spectrometers. Spectral assignments confirmed the presence of several conformers with comparable stability and pointed out possible Coriolis resonance effects between some of them.

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“…The optimized geometries that were found are displayed in Figure 1. The optimized geometries are reported in Table I along with comparison with the microwave experimental values for some geometrical structural parameters of the s-trans conformer obtained by Mehrotra w x et al 9 . The MP2-level calculation produces values within estimated experimental uncertainty for the s-trans conformer for the C᎐C and C᎐N bond lengths, as well as the bond angles ЄC᎐C᎐N, ЄC᎐C᎐C, and ЄC᎐N᎐H.…”

Section: Computational Detailsmentioning

confidence: 99%

Infrared spectra of some isotopomers of isopropylamine: A theoretical study

Zeroka

Jensen

Samuels

1999

Int. J. Quant. Chem.

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ABSTRACT:The normal-mode frequencies and the corresponding vibrational assignments of some isotopomers of isopropylamine are examined theoretically using the Gaussian 94 set of quantum chemistry codes at the MP2 level of theory using a 6-311g** basis set. In particular deuteration of the NH hydrogen atoms as well as the deuteration 2 of the CH hydrogen atoms, the ␣-CH hydrogen atom, and various combinations of 3 deuteration of isopropylamine are examined. Correction factors for predominant vibrational motions are reported and compared for a number of isotopomers of s-transand gauche-isopropylamine. Comparison of theoretically predicted infrared spectra with experimental spectra is made for isotopomers for which experimental data exist. Enthalpy, entropy, and Gibbs free energy changes are considered for the trans ª gauche transformation. An amino torsional potential is deduced and barrier heights are calculated for the trans ª gauche, gauche ª trans, and gauche ª gauche transformations.

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Microwave spectrum, structure, dipole moment, and quadrupole coupling constants of isopropylamine

Cited by 21 publications

References 16 publications

Molecular mechanics (MM4) study of amines

Molecular mechanics (MM4) study of amines

Rich Collection of n-Propylamine and Isopropylamine Conformers: Rotational Fingerprints and State-of-the-Art Quantum Chemical Investigation

Infrared spectra of some isotopomers of isopropylamine: A theoretical study

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