- Investigation of Structure-Property Relationships of Three Nitroaromatic Compounds: 1-Fluoro-2,4,6-trinitrobenzene, 2,4,6-Trinitrophenyl Methanesulfonate, and 2,4,6-Trinitrobenzaldehyde
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Recently the investigation of the correlation between the crystal structure and important properties such as the sensitivity and thermostability of energetic materials has gained more and more interest among experts in the field. To contribute to this development, several models for the sensitivity prediction of energetic materials have been applied to the title compounds. Very often, older models that focus on bond dissociation enthalpy or electrostatic potential result in values that differ significantly from values of actual measurements. However, more recent models such as Hirshfeld surface analysis and fingerprint plot analysis offer an improved correlation between prediction and practical tests. We compared these methods with the aforementioned older models and gained further insight into the structure-property relationships of energetic materials. The accuracy of predictions of structure-property relationships that can be deduced from a crystal structure increases with the sample size over time. Therefore, this method should be pursued and applied to different energetic materials in the future, for a better understanding of those relationships.
- Dosch, Dominik E.,Reichel, Marco,Born, Max,Klap?tke, Thomas M.,Karaghiosoff, Konstantin
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- Formation constants in C-H hydrogen bonding. 4. Effects of cyano, nitro, and trifluoromethyl substituents in aromatic compounds
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Formation constants ( Keq) have been measured using 1H NMR for H-bond complexes with HMPA in CCl 4of 35 aromatic compounds variously substituted with cyano, nitro, and trifluoromethyl groups; several compounds contained F and Cl. The three strongly polar groups enhance H-bonding significantly, usually in the order NO2 > CN > CF3; all are superior to Cl and F. 1,3,5-Trinitrobenzene fails to H-bond at all; however, TNT, its tert-butyl analog, and trinitro-m-xylene show significant Keq values. Coplanarity of nitro groups with the ring blocks approach of HMPA, probably via intramolecular H-bonds. The buttressing effect is evident in some crowded compounds.
- Lorand, John P.
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p. 186 - 205
(2015/02/19)
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- Preparation process of fluorine substituted aromatic compound
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A preparation process of a fluorine substituted aromatic compound comprising reacting an alkali metal or alkali earth metal salt of an aromatic compound having a hydroxy group with an organic fluorinating agent is disclosed. As a representative fluorinating agent, a bis-dialkylamino-difluoromethane compound, for example, 2,2′-difluoro-1,3-dimethylimidazolidine, is exemplified. According to the process, an industrially useful fluorinated aromatic compound, for example, a fluorobenzene, a fluorine substituted benzophenone, a fluorine substituted diarylsulfone can be prepared with ease in economy without specific equipment.
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- Reaction pathways for ambident aryloxide O- and C-nucleophiles in SNAr displacement versus Meisenheimer complex formation with picryl halides. Stereoelectronic effects on regioselectivity
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To probe regioselectivity in Meisenheimer complexation, the reaction of two picryl halides (PiX where X = F, Cl) with a series of aryloxide nucleophiles (phenoxide, 2,4,6-trimethylphenoxide and 2,6-di-t-butylphenoxide) were monitored by 1H NMR spectroscopy in dimethyl sulphoxide at ambient temperature and in acetonitrile-dimethoxyethane(MeCN-DME) at low temperature (-40°C). The reactions of both picryl halides with the ambident (oxygen versus carbon) nucleophile, phenoxide ion (PhO-), and 2,4,6-trimethylphenoxide (mesitoxide, MesO-) leads to clean SNAr displacement of X via the oxygen site of the nucleophile to form the respective aryl picryl ethers, i.e. phenyl picryl ether (3a) and mesityl picryl ether (3b). Meisenheimer complex formation at C-1 or C-3 was not detected in these systems. With 2,6-di-t-butylphenoxide (2,6-DTBPhO-), where oxygen attachment of the aryloxide is precluded by the bulky ortho t-butyl groups, para-carbon attachment was found to occur at C-1 to give picryl 2,6-di-t-butylphenol (3d) in competition with C-attack at C-3 to give the respective carbon-bonded Meisenheimer complexes [X = Cl (4) and X = F (5)]. For both picryl halides, the ratio of 3d, the product of C-1 attack, to the product of C-3 attack, 4 or 5, was roughly 7:1. These findings are considered with regard to the nucleofugality of the halide, X, steric hindrance (F-strain) to attack by the aryloxides at the various positions and stereoelectronic stabilization of C-1 adducts afforded by n → σ* donation.
- Manderville, Richard A.,Dust, Julian M.,Buncel, Erwin
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p. 515 - 528
(2007/10/03)
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- Reactions of 1-X-2,4,6-Trinitrobenzenes and 1-X-2,4-Dinitrobenzenes with Hydroxide Ions. Comparison of the Relative Rates of Nucleophilic Attack at Substituted and Unsubstituted Ring-Positions
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Kinetic and equilibrium measurements are reported for the reactions with hydroxide ions of 1-X-2,4,6-trinitrobenzenes (X = H, F, Cl, Br, I) in water and of 1-X-2,4-dinitrobenzenes in dimethyl sulphoxide-water (80:20, v/v).Attack at unsubstituted ring-positions results in the formation of ?-adducts while attack at halogen-substituted positions leads to 2,4,6-trinitro- or 2,4-dinitro-phenolate ions by nucleophilic substitution; the rate constants for these processes are compared.The results provide evidence for two types of steric effects: (i) increasing the size of the halogen atom results in disruption of the planarity of the nitro-groups, giving a general decrease in reactivity at both unsubstituted and halogen-substituted positions; (ii) unfavourable steric and electrostatic repulsion between entering and leaving groups slows the attack of hydroxide at carbon atoms carrying Cl, Br, or I.In water there is evidence for ionization of added hydroxy groups (3)> and for nucleophilic displacement of nitrite by hydroxide within the 3-hydroxy adducts (2) and (3).Contrary to a recent report the reaction of hydroxide ions with nitro compounds to form hydroxy adducts is found to occur without the observation of spectrophotometrically detectable intermediates.
- Crampton, Michael R.,Davis, Antony B.,Greenhalgh, Colin,Stevens, J. Andrew
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p. 675 - 682
(2007/10/02)
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