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Фешин, В. П.; Фешина, Е. В.; Zhizhina, L. I.

doi:10.1023/a:1014236225660

Cited by 4 publications

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“…The distribution of the electron density in these 2-substituted oxygen containing compounds are significantly different and have a character reverse to that observed for the axial and equatorial atoms found in other ring positions (e.g. see [2][3][4][5][6]). …”

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confidence: 72%

“…We have previously studied features of the electronic distribution in α-chloro ethers including the cyclic tetrahydropyran [2] and 1,4-dioxane [3][4][5]. It was found that the O atom markedly increases the p σ -electron density of the axial Cl atom situated geminally to it.…”

Section: -H Axial and Equatorial Bond Lengths (D) And Charges (Q) Onmentioning

confidence: 99%

“…This is explained by the polarization of the C-Cl bond through the action of the M atom directly through the field (e.g. see [3][4][5][6]). 2-Chloro-N-methylpiperidine does not prove an exception.…”

Section: -H Axial and Equatorial Bond Lengths (D) And Charges (Q) Onmentioning

confidence: 99%

“…The total energy of form 10 is 3.5 kJ/mol less than in 9. Upon going from R = H to R = Me the N-C (2) and N-C (6) bond lengths in forms 1 and 2 are virtually the same (1.452-1.455 Å). However, significant changes of the charge of the N atom occur.…”

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confidence: 95%

“…The results of the calculations show that the Cl atom in 3-chloro-N-methylpiperidine TABLE 1. RHF/6-31G(d) Calculations of the Total Energies of Structures 1-10 (E), C-Cl Bond Lengths, C (2) -H and C (6) molecule occupies an equatorial position, as in substituted cyclohexanes. The total energy of form 8 is 8.9 kJ/mol less than in 7 with an axial Cl atom.…”

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confidence: 99%

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Electronic and Spatial Structure of Piperidine and Its Substituted Derivatives from the Results of ab initio Calculations

Фешина

Zhizhina

Фешин

2005

Chem Heterocycl Compd

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The results of non empirical quantum-chemical calculations using the RHF/6-31G(d) and MP2/6-31G(d) methods do not agree with proposals for the axial position of the H atom on the N atom in the piperidine molecule. According to calculations for the N-methylpiperidine molecule and its chloro-substituted derivatives an equatorially placed methyl group is energetically more favored than an axial. The axial C-Cl and C-H bonds in these molecules are longer than the equatorial. The 35 Cl NQR frequencies for the axial Cl atoms are lower than the equatorial. The 35 Cl NQR frequency of the axial chlorine atom in 2-chloro-1-methylpiperidine is anomalously low. This is chiefly due to the high population density of its p σ -orbital and this is a result of the polarization of the C-Cl bond via the N atom unshared electron pair directly through the field. The effect of a similar unshared electron pair on the parameters of the C-Cl bond in the ClCH 2 NH 2 molecule has been studied by the RHF/6-31(g) method for different angles of rotation of the ClCH 2 group around the C-N bond.Keywords: N-methylpiperidine and its chloro-substituted derivatives, piperidine, axial and equatorial atoms, quantum-chemical calculations, 35 Cl NQR frequencies.As a rule, substituted piperidines exist in a chair form (e.g. see [1]). There is conflicting data regarding the relative orientation of a substituent on the nitrogen atom and in the ring. NMR Data is considered to be (e.g. see [1]) the most reliable for the case of R = H and this points to an axial position for the hydrogen atom (Form 1). For R = alkyl all available data indicates an equatorial position for an alkyl group (Form 2).For a substituent in the ring of substituted piperidines as well as in substituted cyclohexanes the generally more favored orientation is an equatorial position. However, in 2-substituted piperidines, as in 2-substituted tetrahydropyrans, 1,4-dioxanes, cyclohexanones, etc, an electron-acceptor substituent usually occupies an axial position (e.g. see [1]). The distribution of the electron density in these 2-substituted oxygen containing compounds are significantly different and have a character reverse to that observed for the axial and equatorial atoms found in other ring positions (e.g. see [2][3][4][5][6]).The aim of our work is to examine by nonempirical, quantum-chemical methods the conformational features of substituted piperidines, the effect of the nitrogen atom on the electron densities of the Cl and H atoms in variously substituted chloro N-methylpiperidines, and also to study the 35 Cl NQR parameters in the latter. For this task we carried out quantum-chemical calculations of the molecular forms 1-10 via full optimization of their geometry by the Hartree-Fock method on a 6-31G(d) split valence basis using the Gaussian 94W program [7].

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confidence: 72%

Section: -H Axial and Equatorial Bond Lengths (D) And Charges (Q) Onmentioning

confidence: 99%

Section: -H Axial and Equatorial Bond Lengths (D) And Charges (Q) Onmentioning

confidence: 99%

mentioning

confidence: 95%

mentioning

confidence: 99%

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Electronic and Spatial Structure of Piperidine and Its Substituted Derivatives from the Results of ab initio Calculations

Фешина

Zhizhina

Фешин

2005

Chem Heterocycl Compd

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Aminophosphines: their chemistry and role as ligands and synthons

Gopalakrishnan

2009

Applied Organom Chemis

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In recent years, research in organophosphorus chemistry has mainly focused in designing newer and better phosphorus ligands for synthesizing novel metal complexes with improved catalytic activities. Aminophosphines [tricoordinate phosphorus(III)-nitrogen systems] are considered as versatile compounds owing to the presence of nitrogen centres which, in principle, can influence additional reactivity features. They are quite sensitive to air and moisture due to the presence of polar P-N bond(s). In spite of this, research in aminophosphine chemistry is gaining momentum day-by-day and this is due mainly to one reason: their rich behaviour as ligands in metal complex chemistry and subsequently in catalysis. Their role as synthons in inorganic heterocyclic chemistry has also helped produce new types of heterocycles. In this paper, the chemistry of simple acyclic aminophosphines (synthesis, characterization, reactivity and applications) is covered and particular focus is given to their ability to form chalcogenides along with their role played as ligands in coordination chemistry and as synthons in inorganic heterocyclic chemistry.

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Electronic and spatial structure of five-membered oxygen-or sulfur-containing cyclic phosphorus and arsenic compounds based on quantum-chemical calculations

Фешин

Фешина

Zhizhina

2006

Chem Heterocycl Compd

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We have carried out nonempirical quantum-chemical calculations for five-membered heterocyclic molecules containing O or S atoms and also P or As atoms in the ring, using RHF/6-31G(d) and MP2/6-31G(d) methods with full optimization of their geometry. We have studied their electronic and spatial structure and the characteristics of the interaction between atoms in the molecules.Keywords: five-membered oxygen-or sulfur-containing cyclic phosphorus and arsenic compounds, quantum chemical calculations, electronic and spatial structure.For oxygen-containing compounds 1 and 2, the 35 Cl NQR frequencies at 77 K are significantly lower than for the corresponding sulfur-containing analogs 3 and 4 (Table 1) [1, 2], which indicates higher electron densities on the Cl atoms in 1 and 2. This is explained by the fact that the sulfur atom is leas capable of p π -σ conjugation than the oxygen atom [2]. We hypothesize that such a ratio of the NQR frequencies and electron densities for these oxygen-and sulfur-containing compounds is because of polarization of the Z-Cl bonds due to the action of the charge on the S or O atom directly through the field, as in other compounds containing a nonlinear triatomic group Y-Z-M or Y-Z=M (see, for example, [3][4][5][6]). The negative charge on the oxygen atoms in molecules 1 and 2 should be significantly higher than on the sulfur atoms in molecules 3 and 4, which also should lead to the observed ratio of electron densities on the Cl atoms and the NQR frequencies for these compounds. Cl H H H H M(1) M(2) Z C(1) C(2) 1-4 1 Z = P, M(1) = M(2) = O; 2 Z = As, M(1) = M(2) = O; 3 Z = P, M(1) = M(2) = S; 4 Z = As, M(1) = M(2) = S

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Cited by 4 publications

References 1 publication

Electronic and Spatial Structure of Piperidine and Its Substituted Derivatives from the Results of ab initio Calculations

Electronic and Spatial Structure of Piperidine and Its Substituted Derivatives from the Results of ab initio Calculations

Aminophosphines: their chemistry and role as ligands and synthons

Electronic and spatial structure of five-membered oxygen-or sulfur-containing cyclic phosphorus and arsenic compounds based on quantum-chemical calculations

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