Nuclear magnetic resonance spectral parameters and ring interconversion of a series of piperazines

Lett, R.G.; Petrakis, L.; Ellis, Alan F.; Jensen, R. K.

doi:10.1021/j100708a016

Cited by 46 publications

(13 citation statements)

References 6 publications

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“…An "AX pattern" rather than a AA'BB' or AA'XX' pattern was observed. In fact, a well-defined AA'BB' or AA'XX' pattern was not observed even at -100°C in piperazine (25). A somewhat similar "two doublets" pattern has been reported in a synthesized spectrum of the ring protons of piperazine at -100°C in ethanol-methylene chloride using vo6,, = 9.6 Hz taken from the 100 MHz results (25).…”

Section: X-ray Crystallographic Analysissupporting

confidence: 71%

“…A previous nmr study of N,N1-diphenylpiperazine has shown that ring inversion is so rapid that resolution of the peaks of equatorial and axial protons is impossible even at -100°C (25). An AA'BB' or AA'XX' pattern is expected to be observed in the nmr spectra of N,N1-disubstituted piperazines when the ring proton interconversion has been "frozen out" (25, 31 a).…”

Section: X-ray Crystallographic Analysismentioning

confidence: 96%

“…Results and discussion Although some of the N,N1-diarylpiperazines have been characterized previously by their nmr and mass spectra (24)(25)(26), a thorough investigation of the spectral properties of their corresponding hydrated N,N '-dioxides has not been available. The assignment of the ir spectra shown in Table 1 was done with reference to that of piperazine (27,28) and the scheme proposed in the literature (29,30).…”

Section: X-ray Crystallographic Analysismentioning

confidence: 99%

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Synthesis and structural characterization of N,N′-diarylpiperazine N,N′-dioxide tetrahydrates (aryl = o-tolyl, p-tolyl, p-chlorophenyl)

Kwok¹,

Mak²

1988

Can. J. Chem.

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The synthesis and X-ray structure determination of N,N′-di(o-tolyl)piperazine N,N′-dioxide tetrahydrate, I, N,N′-di(p-tolyl)piperazine N,N′-dioxide tetrahydrate, II, and N,N′-di(p-chlorophenyl)piperazine N,N′-dioxide tetrahydrate, III, are described. Compound I crystallizes in space group [Formula: see text] with a = 7.778(1), b = 7.915(2), c = 8.919(2) Å, α = 106.25(2), β = 99.56(1), γ = 108.80(2)°, and Z = 1. Compound II crystallizes in space group [Formula: see text] with a = 6.558(1), b = 7.134(2), c = 11.610(3) Å; α = 73.23(2), β = 78.08(2), γ = 72.67(2)°, and Z = 1. Compound III crystallizes in space group P21/c with a = 9.159(3), b = 12.390(4), c = 8.339(4) Å, β = 97.38(3)°, and Z = 2. The structures of I–III were solved by the direct method and refined to R = 0.049 (1749 observed MoKα reflections), 0.055 (2651 observed reflections), and 0.035 (1827 observed reflections), respectively. In each case, the N,N′-dioxide molecule occupies a site of symmetry [Formula: see text]. The piperazine ring takes the chair form, with two N—O bonds oriented axially in a trans configuration. The structures are characterized by strong hydrogen bonding between the water molecules, as well as between the N-oxide groups and water molecules, giving rise to puckered layers composed of various combinations of edge-sharing four-membered, six-membered, ten-membered, and twelve-membered rings. The aryl rings, which protrude on both sides of each puckered layer, constitute hydrophobic regions separating the hydrophilic layers in the crystal packing.

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Section: X-ray Crystallographic Analysissupporting

confidence: 71%

Section: X-ray Crystallographic Analysismentioning

confidence: 96%

Section: X-ray Crystallographic Analysismentioning

confidence: 99%

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Synthesis and structural characterization of N,N′-diarylpiperazine N,N′-dioxide tetrahydrates (aryl = o-tolyl, p-tolyl, p-chlorophenyl)

Kwok¹,

Mak²

1988

Can. J. Chem.

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“…Chair conformation was found to be the most stable conformer and Hendrickson proposed that for chair-chair interconversion the most stable transition state would be one of the possible chair forms [36,37]. Other conformations that differ from the chair were not considered because of their high energy.…”

Section: Molecular Structurementioning

confidence: 99%

Ab initio Hartree–Fock and density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one

Sıdır

Taşal

et al. 2010

Journal of Molecular Structure

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a b s t r a c tIn the present work, the conformational analysis of 3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)-benzo[d]thiazol-2(3H)-one molecule (abbreviated as 3MOT) was performed by using ab initio HartreeFock (HF) method with 3-21G as the basis set to find the most stable form of 3MOT. Seven staggered stable conformers were observed on the torsional potential energy surfaces. It is shown that 3MOT_1 conformer (D1 = 68.1°, D2 = 73.4°, D3 = À177.4°and D4 = À79.9°) is the most stable form which has chair conformation with the methyl group linked to nitrogen in the axial position. The geometrical parameters, vibrational frequencies and IR intensities of 3MOT were calculated by DFT(B3LYP) method using 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-311G(d), 6-311+G(d), 6-311G(d,p) and 6-311++G(d,p) basis sets for the lowest energy conformer. The solid-state FT-IR spectra was recorded and compared with scaled frequency values. Many normal vibrational bands have been observed to be mixed because of the lacking of symmetry. Determination of the relative weight contribution of each vibrational mode of the observed frequencies indicates the reliability and precision of the spectral analysis. The observed and calculated vibrational frequencies are found to be in good agreement.

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“…Chair conformation was found to be the most stable conformer and Hendrickson proposed that for chair-chair interconversion the most stable transition state would be one of the possible chair forms (Fig. 2) [17,18]. Thus, the obtained optimized geometrical parameters (Table 2) confirm the chair conformation of HEPIPO.…”

Section: Structure Descriptionmentioning

confidence: 52%

Synthesis and Physico-Chemical Studies of a New Noncentrosymmetric Bis[N-(2-hydroxyethyl)piperazine-1,4-diium] Tetrakis(hydrogen oxalate) Trihydrate: [C6H16N2O]2(HC2O4)4·3H2O

2015

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The new noncentrosymmetric oxalate with the general formula [C 6 H 16 N 2 O] 2 (HC 2 O 4 ) 4 Á3H 2 O, has been synthesized and single crystals were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction study on grown crystal reveals that they belong to triclinic system with space group P1. The unit cell dimensions are: a = 5.688 (2) (3) Å 3 and Z = 1. The structure has been solved using a direct method and refined to a reliability R factor of 0.052. The structure is built up from anionic chains parallel to the a-axis. These chains are interconnected by the organic cations and water molecules via hydrogen bonds so as to build a three dimensional arrangement. FT-IR spectrum confirms the presence of the functional groups in the synthesized material. The 13 C CP-MAS NMR spectrum is in agreement with the X-ray structure. UV-Vis spectrum indicates that the crystal is transparent in UV and visible region with a lower cutoff wavelength of 212 nm. The DSC curve indicates that the crystal is thermally stable up to 330 K. Graphical Abstract The molecular structure of bis(N-(2-hydroxyethyl)piperazine-1,4-diium) Tetrakis(hydrogen oxalate) Trihydrate is formed by N-(2-hydroxyethyl)piperazine-1,4-diium cations, oxalate anions and water molecules held together by means of N-H_O, C-H_O, O-H_OW and OW-H_OW(O) hydrogen bonds to form three-dimensional network.

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Nuclear magnetic resonance spectral parameters and ring interconversion of a series of piperazines

Cited by 46 publications

References 6 publications

Synthesis and structural characterization of N,N′-diarylpiperazine N,N′-dioxide tetrahydrates (aryl = o-tolyl, p-tolyl, p-chlorophenyl)

Synthesis and structural characterization of N,N′-diarylpiperazine N,N′-dioxide tetrahydrates (aryl = o-tolyl, p-tolyl, p-chlorophenyl)

Ab initio Hartree–Fock and density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one

Synthesis and Physico-Chemical Studies of a New Noncentrosymmetric Bis[N-(2-hydroxyethyl)piperazine-1,4-diium] Tetrakis(hydrogen oxalate) Trihydrate: [C6H16N2O]2(HC2O4)4·3H2O

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