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studying of the phenomenon of internal rotation in n-mononitroalkilnyh radicals

Electronic structure n-mononitroalkilnyh radicals CeH2 (CH2) nNO2интересно that in electronic density ρ (r) their endgroups two diffuse clouds - not coupled electron е* in CeH2и not divided pairs oxygen in NO2 are located.

VzaiYOmodejstvie (linking) of these clouds result ins to change in ρ (r) in comparison with n - mononitroalkanami [2], N-ALKANES and n-alkilnymi radicals [10]. Redistribution ρ (r) influences all properties CeH2 (CH2) nNO2, including, and on internal rotation characteristics (factors of potential functions V (φ) and barriers conformational peyorehodov V). Earlier it has been shown, that radical centre CeH2 (Chapter 3 and [4, 3, 24]) okazyyovaet essential influence on parametres V (φ) and barriers of two communications C-C going successively in n-alkilnyh radicals (Chapters 2 see, 3 and [10]). Is of interest to track podobyonye changes in molecules CeH2 (CH2) nNO2, containing heteroatoms, to position zakoyonomernosti, connected directly and with rotation of the radical centre and it vzaiyomodejstviem with not hydrocarbonaceous group, and also to compare the received results with inductive effects of nuclear groupings in molecules of alkanes and mononitroalkayonov [10, 2].

Potential functions V (φ) n-trans-mononitroalkilnyh radicals (only 44 functions, Table 4.116 4.120) have been calculated for all internal rotations in CeH2 (CH2) nNO2 where n = 0 7, method B3LYP∕6-311 ++ (3df, 3pd), and also in initial goyomologah by means of MP2∕6-311 ++ (3df, 3pd) by means of program GAUSSIAN [226] in the Cartesian basis 6d 10f the Step of co-ordinate of reaction - two-sided angle φ - made 10 . For each rotation positions and values full energy perehodyonyh conditions and local minima - extremums of a surface potential eneryogii (SHHE) have been specified. Transient states are found by means of procedure QST3 [492, 493]. poyogreshnost numerical calculation of full energy Etotalне exceeded 1? 10-10а.е. (Less than 1 Dzh/MOLE), and elements of a matrix of density 3? 10-6. Proceeding from it, factors razloyozhenija V (φ) abreast Fouriers of Table 4.116 4.120 are resulted to within 1 Dzh/MOLE. Functions V (φ) at rotation about communication C-N are approximated by a number (4.142) with n = 2, and round communications C-C, as in the form of decomposition (4.142) with n = 1, and (4.167)

Molecule CeH2NO2 - initial homologue of a number - flat (it agree B3LYP∕6 - 311 ++ (3df, 3pd) and MP2∕6-311 ++ (3df, 3pd)), and its structure falls into to point group C2v. Close arrangement CeH2и NO2в the yielded connection result ins strong vzaimodejyostviju electronic clouds of trailer oxygen and free valency - them soyoprjazheniju (see the Chapter III), that is expressed in the significant size of barrier Vglob equal
29.07 and 22.66 kdzh/MOLE (B3LYP and MP2 accordingly, Table 4.116). We will notice, that if in mother compound with a selfcontained cover (CH3NO2) size Vgιob calculated poyosredstvom МР2 (0.05 kdzh/MOLE), exceeds that for DFT (0.03 kdzh/MOLE), in C*H2NO2наблюдается the return.

The specified lifting of a barrier in C*H2-No2predpolagaet an explanation in terms of "stabilising linking, as in initial molecule Ch3-No2barer VgIobна two orders less (see above and [1]). As well in C*H2-CH3 where peyorekryvaetsja inductive influence of endgroups, but is absent linking, Vglobмал and 0.23 kdzh/MOLE [4] is equal. Approximating (4.142) points of section PPE found with pomoyoshchju MP2/6-311 ++ (3df, 3pd) for C*H2-NO2, result ins to badly converging number (4.142 [1] that is reflected in value are nonviscous Δ ≈ 1 kdzh/MOLE, (at B3LYP in 5 times it is less). KoeffitsiYOenty V (φ) in that and other decomposition (MP2 and DFT) are significant (Table 4.116). It speaks about essential redistribution ρ (r) at change of two-sided angle φ, connected, in bolshej to a measure, with the form curve V (φ) (Drawing 4.19).

The phenomenon of "linking" essentially increasing a barrier of rotation, from the point of view of quantum mechanics can be presented as consequence of distribution chayosti Pe. (r) in basins of the next groups, in this case NO2, and on the contrary (see Chapter 2).

Interaction of kernels with the electronic density distributed on different basins, stabilises structure (stiffens it). Kernels "feel" each other posredyostvom delokalizovannoj ρ (r). Such interaction affects all distribution rg), and not just on local parts pR (r), where R - fragments making a molecule, causing the co-ordinated movement of kernels and result ining significant work on them peremeshcheyoniju in electronic clouds - to internal rotation barriers (Drawings 4.19 and 4.20).

The barrier of turn of group NO2 (Table 4.116, Drawing 4.21) at following homologue C2H4-No2rezko decreases till 0.60 a kdzh/MOLE (0.37 kdzh/MOLE also is small and equal in mother compound C2H5-No2on [1]). Most likely, it is connected with increased lokalizatsiyoej not coupled electron е* on radical centre S*N2 (Chapters 2 and 3 see) and smaller perturbation pm, ι (r) from the side е*. I.e. kernels turn together with electron atmospheres falling into with it pR (r), and the basic deformation ρ (r) occurs in the field of communication. In the subsequent molecules nitrogroup rotation (since C3H6-NO2) is weak zayovisit from chain length, and, hence, from distribution of electronic density, otnoyosimoj to е* (Table 4.116, Drawing 4.21 see). With increase in number of groups SN2 the parametres describing internal rotation, converge quickly to corresponding sizes in n - alkanes, n-alkilnyh radicals [4, 3, 24] and n-nitroalkanes [1]. So, characteristics vrayoshchenija groups NO2 in initial molecules and radicals coincide (with the account pogreshnoyo
sti), since CeH2 (CH2) 5-No2i CH3 (CH2) 3-NO2. I.e. electronic density nitrogrupyopy pNO (it is poorly subject to action of the next groups, that allows to use for it the term "isolation" (compactness pNO (r)). The Same concerns and system of atoms CeH2CH2 - (the previous partitions and [4] see also). Similar supervision result in survivabilities NO2и of other fragments, and from here to shipping of their partial properties, including, falling into to internal rotation.

Linking infringement between electron atmospheres of endgroups not otmeyonjaet their interactions, though and weakened by inclusion between them "neutral" fragments CH2. Display of it is the double gosh-effect [232] in CeH2 (CH2) 3NO2 - equality energy a trance and gosh "conformstions at rotation about communications CeH2CH2 - (CH2) 2NO2и CeH2 (CH2) 2-CH2NO2 (see more low), and also difference in structure CeH2 (CH2) nNO2, with n

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A source: Turovtsev Vladimir Vladimirovich. Creation and application of a quantum mechanical model for calculating the thermodynamic properties of substances in a wide range of temperatures. Thesis for the degree of doctor of physico-mathematical sciences. Tver - 2014. 2014

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