2-甲氧基-3-氟-4-碘吡啶的合成

2-甲氧基-3-氟-4-碘吡啶是一个重要的医药化工中间体,其合成路线未见文献报道。以2-甲氧基-3-氟-5-氯吡啶为起始原料,经氢解和碘代两步反应合成标题化合物,总收率62.8%,其结构经¹H NMR, ¹³C NMR和MS确证。     

Density functional theory studies on vibrational and electronic spectra of 2-chloro-6-methoxypyridine

The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-6-methoxypyridine have been recorded in the range 3700-400 and 3700-100 cm(-1), respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound was carried out using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound. The geometry and normal modes of vibration obtained from the DFT methods are in good agreement with the experimental data. The normal co-ordinate analysis was also carried out using DFT force fields utilising Wilson's FG matrix method. The influence of the substituents bulky chlorine atom and the methoxy group on the spectral characteristics of the compound has been discussed. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.     

Infrared and Raman spectra and thermodynamic functions of 4-methoxypyridine N-oxide

The infrared spectrum of 4-methoxypyridine N-oxide in the region 4000-30 cm⁻¹ in the solid and liquid states and the polarized laser Raman spectrum of the molecule in the liquid state have been investigated. A vibrational assignment of the observed frequencies based on the state of polarization of the Raman lines and comparison with the related molecules is presented. Ideal gas state thermodynamic functions of the molecule are calculated in the temperature range 273·15–1500° K.     

Pulse radiolysis of 3-pyridine methanol and 3-pyridine carboxaldehyde in aqueous solutions

Reactions of e_aq ^-, H-atom and OH radicals with 3-pyridine methanol (3-PM) and 3-pyridine carboxaldehyde (3-PCA) have been studied at various pHs using pulse radiolysis technique. e_aq ^- was found to be highly reactive with both 3-PM and 3-PCA (k approx. 10¹⁰ dm³ mol 1 s^-1). Semi-reduced species formed in both cases were strongly reducing in nature. In the case of 3-PM, electron addition leads to the formation of pyridinyl radicals whereas in the case of 3-PCA, PyCHOH type radicals are formed. At pH 6.8, H-atom reaction with 3-PCA also gives semi-reduced species (PyCHOH), whereas at pH 1, H-atoms add to the ring. (CH₃)₂ ^·COH radicals were found to transfer electron to 3-PCA at all the pH values tested and by making use of changes in the absorption spectra, pK _a values of the semi-reduced species were determined to be 4.5 and 10.6. OH radicals were found to undergo addition reaction with 3-PCA, whereas in the case of 3-PM they reacted by H-abstraction as well as addition reaction. By following the yield of methylviologen radical cation formed by electron transfer reaction, it was estimated that approx. 50% of OH radicals react with 3-PM by H-atom abstraction at pH 6.8, giving reducing radicals, whereas at pH 3.2, where 3-PM is in the protonated form, the same is only about 10%. At pH 13, O^-· radical anions were found to react exclusively by H-atom abstraction. Reaction of SO₄ ^-· radicals with 3-PCA was found to give a species identical to the one formed by one electron reduction of nicotinic acid at acidic pH values.     

Electronic spectra of 2-acetylanthracene

The electronic spectrum of 2-acetylanthracene in a supersonic free jet reveals the existence of two rotational isomers with ≈ 196 cm⁻¹difference between their S₁ origins. In low-temperature rigid glasses, 2-acetylanthracene forms stable dimers. The probable structure of this dimer is also briefly discussed.     

Pulse radiolysis of 3-pyridine methanol and 3-pyridine carboxaldehyde in aqueous solutions

Reactions of e_aq^-, H-atom and OH radicals with 3-pyridine methanol (3-PM) and 3-pyridine carboxaldehyde (3-PCA) have been studied at various pHs using pulse radiolysis technique. e_aq^- was found to be highly reactive with both 3-PM and 3-PCA (k approx. 10¹⁰ dm³ mol¹ s^-1). Semi-reduced species formed in both cases were strongly reducing in nature. In the case of 3-PM, electron addition leads to the formation of pyridinyl radicals whereas in the case of 3-PCA, PyCHOH type radicals are formed. At pH 6.8, H-atom reaction with 3-PCA also gives semi-reduced species (PyCHOH), whereas at pH 1, H-atoms add to the ring. (CH₃)₂˙COH radicals were found to transfer electron to 3-PCA at all the pH values tested and by making use of changes in the absorption spectra, pK_a values of the semi-reduced species were determined to be 4.5 and 10.6. OH radicals were found to undergo addition reaction with 3-PCA, whereas in the case of 3-PM they reacted by H-abstraction as well as addition reaction. By following the yield of methylviologen radical cation formed by electron transfer reaction, it was estimated that approx. 50% of OH radicals react with 3-PM by H-atom abstraction at pH 6.8, giving reducing radicals, whereas at pH 3.2, where 3-PM is in the protonated form, the same is only about 10%. At pH 13, O^-˙ radical anions were found to react exclusively by H-atom abstraction. Reaction of SO₄^-˙ radicals with 3-PCA was found to give a species identical to the one formed by one electron reduction of nicotinic acid at acidic pH values.     

3-羟基-2-吡啶亚胺异构反应的机理

在RHF-6-31G,MP2/6-31G和MP2/6-31G水平上,对3-羟基-2-吡啶亚胺的气相、水分子作为催化剂的异构化反应进行了研究,结果表明,气象异构难于进行,水分子作为催化剂参与反应过程是目标反应所循的反应路径。     

Electronic absorption spectra of 3-hydroxypyridine and 5-hydroxypyrimidine

The electronic absorption spectra ( ^* type) of the mixture of the enolic and zwitterionic forms of both 3-hydroxypyridine and 5-hydroxypyrimidine are interpreted by means of the Pariser-Parr-Pople type calculations.     

Electronic spectra of the 2-oxypurine isomers

The Pariser-Parr-Pople type calculations were carried out for tautomeric isomers of 2-oxypurine. The calculated transition energies for the keto form (III) of this compound are in a good agreement with the observed absorption spectrum.     

Electronic absorption spectra of arylmethylene, ethylidene, and allylidene 3H-furan-2-one derivatives

The electronic absorption spectra of 3H-furan-2-ones containing substituents with varied length of the conjugation chain in position C³ of the heteroring are examined. The conclusions are made about the direction of the band shift depending on the structure and size of the conjugation system of the substituents.     

Electronic absorption spectra of 3-chloro- and 3-amino-1,2,4-triazole derivatives

The manifestation of acid-base interactions in the electronic absorption spectra of 32 1,2,4-triazole derivatives was studied. Ionization of the heteroring does not have a substantial effect on the energies of the electron transitions of 3-chloro-5-substituted 1,2,4-triazoles but causes changes in the extinctions of the absorption bands of 3-amino-5-substituted triazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 546–548, April, 1977.     

Electronic absorption spectra of V2O5

MO calculations of electronic structure and optical transitions for [VO_n]^{5 ?; 2n} (n = 4, 5, 6) clusters in V₂O₅ monocrystals have been carried out by means of the semiempirical CNDO CI method. Using the calculated results, a complete analysis of V₂O₅ optical data as available in the literature and as obtained in the electroreflectivity experiments presented in this paper is performed. An identification of optical transitions in a wide energy range is presented. The optical properties of vanadium pentoxide are shown to be due to the localized charge transfer electronic transitions in the clusters. The fine structure of optical spectra is connected with the covalent splittings of the vanadium 3d and oxygen 2p atomic levels.     

The preparation of 3-hydrazino-4-hydroxy- and 3-hydrazino-4-methoxypyridine from sydnones

3-Hydrazino-4-hydroxy- and 3-hydrazino-4-methoxypyridines, which could not be obtained by reduction of the corresponding diazonium salts, have seen prepared by decomposition of N-(4-substituted-pyrid-3-yl)-syndones.     

Electronic absorption spectra of 2-amino-6-nitro-, 4-amino-3-bromo-and 5-amino-2-bromotoluenes

A new technique—photoacoustic spectroscopy—has been used for the first time to record the u.v.-vis spectra of three substituted toluenes, namely 2-amino-6-nitrotoluene, 4-amino-3-bromotoluene and 5-amino-2-bromotoluene. The π-π* electronic transitions analogous to the benzene first primary and secondary transitions could be detected from the PAS spectra in comparison with the u.v. solution and vapour spectra recorded by conventional methods. Detection of singlet → triplet absorptions from the PAS spectra, with significant intensity, is considered to be an important feature which transitions are in general either not observed or observed with only very weak intensity, in solution or vapour, by conventional methods. The analysis shows that a few excited state combinations observed in the u.v. PAS spectra of the molecules presently studied are well comparable with such combinations in ground state observed in the near i.r. PAS spectra.     

Redox reactions of transient species formed during pulse radiolysis of 2-pyridine carboxaldehyde and 2-pyridine methanol in aqueous solutions

Rate constants for the reactions of e _aq ^? , H and OH radicals with 2-pyridine carboxaldehyde and 2-pyridine methanol have been determined by pulse radiolysis technique. Reactions of reducing radicals such as acetone ketyl radicals and CO₂ ^? with these compounds were also evaluated at various pHs. The species produced by the reaction of reducing radicals with these solutes was a strong reductant itself. While pyridinyl were produced in the case of 2-pyridine methanol, one-electron reduction of 2-pyridine carboxaldehyde led to the formation of PyCHOH radical. The one-electron reduction potential of PyCHOH radicals was estimated by establishing an equilibrium with MV⁺ radical cations to be ?0.6V vs NHE. OH radical reaction with 2-pyridine carboxaldehyde gave an OH adduct, while in the case of 2-pyridine methanol, OH radicals reacted partly by H-abstraction from the ?CH₂OH group. SO₄ ^? radical reaction with 2-pyridine carboxaldehyde produced a species which was reducing in nature. The rate constants for the reaction of e _aq ^? and OH radicals are compared with similar values obtained in the case of other 2-pyridine derivatives to see if there is any electron-inductive effect.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2-pyridinamine

The u.v. absorption and fluorescence spectra of 2-pyridinamine, its methyl derivatives and its carboxylate salts were measured in various solvents (isooctane, methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, acetic acid and isooctane mixed solvent, and pH adjusted solvent) at room temperature and 77 K. These spectral data were interpretated by the molecular orbital method. From these results it was found that the formation of 2(1H)-pyridinimine with the accompanying 2-pyridinium amine occurs only in the π,π* excited singlet state in the acetic acid and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2-pyridinamine in the pH ⪢ 11 controlled solution was assigned to the monoanion species, that is, the 2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

Electronic spectra of nitroethylene

A systematic study of the electronic excited states of nitroethylene (C₂H₃NO₂) was carried out using the approximate coupled‐cluster singles‐and‐doubles approach with the resolution of the identity (RI‐CC2), the time dependent density functional theory with the CAMB3LYP functional (TDDFT/CAMB3LYP) and the DFT multireference configuration interaction (DFT/MRCI) method. Vertical transition energies and optical oscillator strengths were computed for a maximum of 20 singlet transitions. Semiclassical simulations of the ultraviolet (UV) spectra were performed at the RI‐CC2 and DFT/MRCI levels. The main features in the UV spectrum were assigned to a weak n‐π* transition, and two higher energy π_CC+O‐π* bands. These characteristics are common to molecules containing NO₂ groups. Simulated spectra are in good agreement with the experimental spectrum. The energy of the bands in the DFT/MRCI simulation agrees quite well with the experiment, although it overestimates the band intensities. RI‐CC2 produced intensities comparable to the experiment, but the bands were blue shifted. A strong π_CC+O‐π* band, not previously measured, was found in the 8–9 eV range. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012