- One-pot process for preparing acetic acid -2, 5 -dimethylphenyl ester and 2,5 -dimethylnitrobenzene (by machine translation)
-
The method comprises the following steps of: adding acetic anhydride in a single-mouth flask; adding additional p-xylene; adding the reaction solution obtained in Step III to a separatory funnel; stirring the reaction; cooling to room temperature; and quenching the reaction solution obtained in the step three steps: adding deionized water, stirring the reaction and cooling to room temperature; and quenching the reaction solution in step three steps: adding deionized water, stirring the reaction and cooling to room temperature; and thirdly, distilling the reaction solution obtained in the step three steps into dichloromethane to volatilize to obtain a product, namely acetic acid -2 -2, 5 - 5 -dimethylphenyl ester 2,5 - and 2,5 -dimethylnitrobenzene. To the method, nitrate is used as an oxidant and a nitrate agent, the price is low,2-dimethylnitrobenzene can be obtained while the acetic acid 5 - and 2,5 -dimethylphenyl ester are obtained, two products can be obtained through one-step reaction, and the utilization rate of the raw material is improved. (by machine translation)
- -
-
Paragraph 0021-0041; 0046
(2020/06/16)
-
- Method and device for preparing methylnitro-benzene by channelization
-
The invention discloses a method and a device for preparing methylnitro-benzene by channelization. The device comprises a storage tank, a nitrogen dioxide cylinder, an ozone generator, a flow pump, agas flowmeter, a reaction pipeline filled with a catalyst, a mixing pipeline, two T-shaped mixed joints, a cooling system, a heating system, a back pressure valve and a receiving tank. The method specifically comprises the following steps: opening the cooling system and the heating system; opening the ozone generator; arranging the flow pump and the gas flowmeter; and mixing raw materials liquid methyl benzene and nitrogen dioxide through the first T-shaped mixing joint and feeding the mixture into the mixing pipeline, then mixing the mixture with ozone in the second T-shaped mixing joint, feeding the mixture into the reaction pipeline filled with the catalyst for a nitrifying reaction, and post-treating a reaction liquid to obtain methylnitro-benzene. The method is controlled precisely and automatically, and is simple to operate, mild in reaction condition, simple in post treatment, quick to transfer mass and heat, high in safety and good in economical benefit.
- -
-
Paragraph 0053; 0054; 0055
(2019/02/04)
-
- Hydrophobic WO3/SiO2 catalyst for the nitration of aromatics in liquid phase
-
WO3/SiO2 solid acid catalyst synthesized using sol gel method has shown promising activity (up to 65% conversion) for aromatic nitration in liquid phase using commercial nitric acid (70%) as nitrating agent without using any sulfuric acid. The water formed during the reaction as well as water from dilute nitric acid (70%) was removed azeotropically, however due to the hydrophilic nature of the catalyst, some water gets strongly adsorbed on catalyst surface forming a barrier layer between catalyst and organics. This prevents effective adsorption of substrate on catalyst surface for its subsequent reaction. To improve the activity further, the hydrophilic/hydrophobic nature of the catalyst was altered by post modification by grafting with commercial short chain organosilane (Dynasylan 9896). The modified 20% WO3/SiO2 catalyst when used for o-xylene nitration in liquid phase, showed significant increase in the conversion from 65% to 80% under identical reaction conditions. Catalyst characterization revealed decrease in the surface area of 20% WO3/SiO2 from 356 m2/g to 302 m2/g after grafting with Dynasylan 9896. The fine dispersion of WO3 particles (2–5 nm) on silica support was not affected due to modification. NMR and FTIR study revealed the decrease in surface hydroxyl groups imparting hydrophobicity to the catalyst. Interestingly the total acidic sites of the catalyst remained almost unaltered (0.54 mmol NH3/g) even after modification. Even though, the acidity and other characteristics of the catalyst did not change appreciably, there was a considerable increase in the o-xylene conversion which can be ascribed to the hydrophobic nature of the catalyst.
- Kulal,Kasabe,Jadhav,Dongare,Umbarkar
-
p. 105 - 113
(2019/02/15)
-
- MOF Decomposition and Introduction of Repairable Defects Using a Photodegradable Strut
-
Photoswitchable components can modulate the properties of metal organic frameworks (MOFs); however, photolabile building blocks remain underexplored. A new strut NPDAC (2-nitro-1,4-phenylenediacetic acid) that undergoes photodecarboxylation has been prepared and incorporated into a MOF, using post-synthetic linker exchange (PSLE) from the structural analogue containing PDAC (p-phenylenediacetic acid). Irradiation of NPDAC-MOF leads to MOF decomposition and concomitant formation of amorphous material. In addition to complete linker exchange, MOFs containing a mixture of PDAC and NPDAC can be obtained through partial linker exchange. In NPDAC30-MOF, which contains approximately 30 % NPDAC, the MOF retains crystallinity after irradiation, but the MOF contains defect sites consistent with loss of decarboxylated NPDAC linkers. The defect sites can be repaired by exposure to additional PDAC or NPDAC linkers at a much faster rate than the initial exchange process. The photoremoval and replacement process may lead to a more general approach to customizable MOF structures.
- Yan, Jingjing,MacDonald, John C.,Maag, Alex R.,Coudert, Fran?ois-Xavier,Burdette, Shawn C.
-
p. 8393 - 8400
(2019/05/28)
-
- HNO3/HFIP: A Nitrating System for Arenes with Direct Observation of π-Complex Intermediates
-
This report describes an efficient nitrating system for the nitration of arenes at room temperature by using an equivalent of nitric acid in HFIP (1,1,1,3,3,3-hexafluoroisopropanol). The π-complex intermediate of an arene with a nitronium ion stabilized by HFIP can be directly observed by UV-vis spectra and is supported by theoretical calculations.
- Lu, Le,Liu, Huixin,Hua, Ruimao
-
supporting information
p. 3197 - 3201
(2018/06/11)
-
- Nucleophilic Nitration of Arynes by Sodium Nitrite and its Multicomponent Reaction Leading to Double-Functionalized Arenes
-
An unusual nucleophilic nitration of arynes by NaNO2 in the presence of water has been developed, and the concept was further demonstrated to accomplish a double functionalization of arynes using a multicomponent reaction protocol to synthesize pharmaceutically important (2-nitrophenyl)methanol derivatives. Such substitution ortho to -NO2 is difficult by other means. The reaction conditions are mild and avoid the use of strong acids, expensive transition metal catalysts, and additives.
- Dhokale, Ranjeet A.,Mhaske, Santosh B.
-
supporting information
p. 3010 - 3013
(2016/07/06)
-
- Poly(4-vinylpyridine)-nitrating mixture complex (PVP-NM): Solid nitrating mixture equivalent for safe and efficient aromatic nitration
-
Friedel-Crafts type aromatic nitration has served as an indispensable reaction within both industrial and academic applications. However, growing concern over the use of copious amounts of strong acids has prompted the search for more environmentally friendly alternatives. Polymer-bound Bronsted acids, on the other hand, have been shown useful as convenient alternatives to liquid acids. Nitric acid and sulfuric acids have, therefore, been combined, both individually and as a mixture, with poly(4-vinylpyridine). The new solid acid systems have been used to nitrate both activated and deactivated arenes under mild conditions and proved to be effective nitrating agent.
- Surya Prakash,Gurung, Laxman,Glinton, Kevin E.,Belligund, Kavita,Mathew, Thomas,Olah, George A.
-
supporting information
p. 3446 - 3451
(2015/06/25)
-
- Regioselective nitration of m-xylene catalyzed by zeolite catalyst
-
Nitration with nitric acid and acetic anhydride via acetyl nitrate as nitrating species is efficient with the substrate m-xylene as solvent. Zeolite Hβ with an SiO2/Al2O3 ratio of 500 was found to be the most active of the catalysts tried both in yield and regioselectivity in the nitration of m-xylene. The molecular volume of the reactants was calculated with the Gaussian 09 program at the B3LYP/6-311+G(2d, p) level and compared with the size of the zeolite Hβ channels. A range of other substrates were subjected to the nitrating system under the same conditions as those optimized for m-xylene and excellent selectivity was obtained.
- Dong, Xiongzi,Peng, Xinhua
-
p. 1122 - 1128
(2016/01/15)
-
- Regioselective preparation of 4-nitro-o-xylene using nitrogen dioxide/molecular oxygen over zeolite catalysts. remarkable enhancement of para-selectivity
-
In the presence of molecular oxygen and zeolite H-β with Si/Al 2 = 500, o-xylene reacted regioselectively with liquid nitrogen dioxide at 35 °C to yield mononitro-o-xylenes as the main product, where the 4-nitro-o-xylene isomer predominated up to 89% and the 4-nitro-/3-nitro-o- xylene isomer ratio improved to 7.8. The process is eco-friendly, less expensive, and the zeolite could be easily regenerated by a simple workup to afford results similar to those obtained with the fresh catalyst.
- Liu, Hongtao,Ji, Cheng,Dong, Xiongzi,Peng, Xinhua,Shi, Chunjie
-
supporting information
p. 817 - 819
(2014/06/23)
-
- Eco-friendly nitration of benzenes over zeolite-β-SBA-15 composite catalyst
-
Direct synthesis of microporous-mesoporous zeolite-β-SBA-15 (ZBS-15) composite catalyst from the synthetic precursors of SBA-15and zeolite-β seeds under acidic hydrothermal conditions through the simultaneous self-assembly of mesoporous silica SBA-15 and zeolite-β has been accomplished and characterized the ZBS-15 catalyst by XRD, N2 sorption, FT-IR, TPD of ammonia and SEM techniques. The activity of the ZBS-15 composite catalyst for the nitration of benzenes under solvent-free conditions has been investigated, which revealed that there is a significant synergistic influence of both zeolite-β and SBA-15 materials on the activity of the ZBS-15 catalyst.
- Ganjala, Venkata Siva Prasad,Neeli, Chinna Krishna Prasad,Pramod, Chodimella Venkata,Khagga, Mukkanti,Rao, Kamaraju Seetha Rama,Burri, David Raju
-
-
- Rapid and efficient solvent-free synthesis of cyclophanes based on bipyridinium under mechanical ball milling
-
We reported here the first rapid and solvent-free template-directed preparation of cyclophanes based on bipyridinium, which was achieved using mechanical ball milling. The method affords a new strategy for construction of diverse substituted CBPQT·4PF6, which greatly shortens the reaction period, rendering this methodology practical in the field of supermolecular chemistry.
- Xi, Hai-Tao,Zhao, Ting,Sun, Xiao-Qiang,Miao, Chun-Bao,Zong, Ting,Meng, Qi
-
p. 691 - 694
(2013/03/28)
-
- Aromatic nitration with bismuth nitrate in ionic liquids and in molecular solvents: A comparative study of Bi(NO3)3·5H 2O/[bmim][PF6] and Bi(NO3)3· 5H2O/1,2-DCE systems
-
A suspension of bismuth nitrate pentahydrate (BN) in [bmim][PF6] or [bmim][BF4] imidazolium ionic liquid (IL) is an effective reagent for ring nitration of activated aromatics under mild conditions without the need for external promoters. Nitration can also be effected in 1,2-DCE, MeCN, or MeNO2 without additives. Nitration of activated arenes (anisole, toluene, ethylbenzene, cumene, p-xylene, mesitylene, durene, and 1,3-dimethoxybenzene) is considerably faster (time to completion) in BN/[bmim][PF6] relative to BN/1,2-DCE and there are also differences in isomer distributions (for anisole, toluene, and ethylbenzene). With introduction of strongly deactivating substituents (-CHO; -MeCO; -NO 2) the BN/IL system is no longer active but reactions still proceed with BN/1,2-DCE in reasonable yields. The ready availability and low cost of BN, simple operation, and absence of promoters, coupled to recycling and reuse of the IL, provide an attractive alternative to classical nitration methods for activated arenes. Switching from Bi(NO3)3·5H 2O/[bmim][PF6] to Bi(NO3)3· 5H2O/1,2-DCE increases the scope of the substrates that can be nitrated.
- Jacoway, Jonathan,Kumar, G. G. K. S. Narayana,Laali, Kenneth K.
-
p. 6782 - 6785,4
(2012/12/12)
-
- Regioselective nitration of aromatics under phase-transfer catalysis conditions
-
Mononitration of aromatics was performed in a two-phase system using phase-transfer catalyst. The most advantageous conditions for the nitration were determined (temperature, reaction time, the type and amount of phase transfer catalyst, nitrification strength of the nitro-sulfuric acid). From the results, a significant improvement in the selectivity and conversion of the nitration of xylene was observed: the ratio of 4-nitro-m-xylene to 2-nitro-m-xylene was unprecedented increased up to 91.3%:7.7%, the ratio of 4-nitro-o-xylene to 3-nitro-o-xylene was also increased to 71.1%:27.2%; both the conversions were over 96%.
- Wang, Peng-Cheng,Lu, Ming,Zhu, Jie,Song, Yan-Ming,Xiong, Xian-Feng
-
experimental part
p. 42 - 47
(2012/01/15)
-
- Pd-catalyzed conversion of aryl chlorides, triflates, and nonaflates to nitroaromatics
-
(Chemical Equation Presented) An efficient Pd catalyst for the transformation of aryl chlorides, triflates, and nonaflates to nitroaromatics has been developed. This reaction proceeds under weakly basic conditions and displays a broad scope and excellent
- Fors, Brett P.,Buchwald, Stephen L.
-
supporting information; experimental part
p. 12898 - 12899
(2009/12/07)
-
- LIGANDS FOR TRANSITION-METAL-CATALYZED CROSS-COUPLINGS, AND METHODS OF USE THEREOF
-
Ligands for transition metals are disclosed herein, which may be used in various transition-metal-catalyzed carbon-heteroatom and carbon-carbon bond-forming reactions. The disclosed methods provide improvements in many features of the transition-metal-catalyzed reactions, including the range of suitable substrates, number of catalyst turnovers, reaction conditions, and efficiency. For example, improvements have been realized in transition-metal-catalyzed cross-coupling reactions.
- -
-
Page/Page column 144-145
(2009/07/17)
-
- Polymer-supported ytterbium perfluorooctanesulfonate [Yb(OPf)3]: A recyclable catalyst for organic reactions
-
Amberlyst A-21, a kind of well-known and cheap polymeric material, was treated with ytterbium perfluorooctanesulfonate [Yb(OPf)3] giving a reagent with a ytterbium loading of 1.34 (wt%). The polymer-supported fluorous ytterbium catalyses the highly efficient nitration, esterification, Fridel-Crafts acylation, and aldol condensation. The catalyst can be recovered by simple filtration and used again without a significant loss of catalytic activity. The protocol avoids the use of fluorous solvents during the reaction or workup, which are expensive and can leach in small amounts.
- Yi, Wen-Bin,Cai, Chun
-
p. 524 - 528
(2008/12/22)
-
- BF3·2CF3CH2OH (BF 3·2TFE), an efficient superacidic catalyst for some organic synthetic transformations
-
BF3 · 2CF3CH2OH complex was found to be a very effective superacidic catalyst comparable in acid strength to at least that of 100% anhydrous sulfuric acid for various acid-catalyzed organic transformations such as isomerizations, rearrangements, ionic hydrogenation of various ketones, and aromatics with triethylsilane and nitration of aromatics with metal nitrate. Studies of the pivalaldehyde-methyl isopropyl ketone rearrangement and the benzopinacol to phenanthrene transformation suggest that the complex has an acidity comparable to that of 100% anhydrous sulfuric acid. The structure and properties of the 1:2 boron trifluoride-trifluoroethanol complex have been further studied using NMR (1H, 13C, 19F, 11B) and DFT calculations at the B3LYP/6- 311++G**//B3LYP/6-31G* level.
- Prakash, G. K. Surya,Mathew, Thomas,Marinez, Eric R.,Esteves, Pierre M.,Rasul, Golam,Olah, George A.
-
p. 3952 - 3958
(2007/10/03)
-
- Supported tetramethylamonium nitrate/silicasulfuric acid as a useful reagent for nitration aromatic compounds under solvent-free conditions
-
A variety of aromatic compounds are nitrated to the parent nitro aromatic compounds under solvent-free conditions using supported tetramethylammonium nitrate/silicasulfuric acid as a useful reagent. This methodology is useful for nitration of activated and deactivated aromatic rings. Copyright Taylor & Francis, Inc.
- Hajipour, Abdol R.,Zarei, Amin,Khazdooz, Leila,Ruoho
-
p. 2237 - 2241
(2007/10/03)
-
- Supported bismuth(III) nitrate on silica sulfuric acid as useful reagent for nitration of aromatic compounds under solvent-free conditions
-
A number of aromatic compounds were nitrated to the corresponding nitroaromatic derivatives with the use of supported bismuth(III) nitrate on silica sulfuric acid under solvent-free conditions.
- Hajipour,Zarei,Ruoho
-
p. 1493 - 1495
(2007/10/03)
-
- Synthesis and characterization of Nitro-p-xylenes
-
In this paper we elected to nitrate p-xylene because this compound has only one mononitro- and trinitro- isomer. Trinitro-p-xylene was used as a starting material for the synthesis of other compounds in subsequent work. The mononitration of p-xylene can be easily carried out at 30°C. Nitro-p-xylene is easily nitrated to dinitro-p-xylene at a temperature of 80°C. The trinitro-p-xylene can be obtained at 120°C. Single crystals of 2,3-dinitro-p-xylene and 2,3,5-trinitro-p-xylene were grown using the slow cooling method and we report the X-ray structure of the former. The thermal decomposition of the compounds was studied using differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) techniques and FT-IR. The target compounds were also characterized by 1H-NMR, 13C-NMR and MS.
- Yan-Hong, Liu,Tong-Lai, Zhang,Jian-Guo, Zhang,Jin-Yu, Guo,Kai-Bei, Yu
-
p. 978 - 989
(2007/10/03)
-
- Lanthanide(III) nosylates as new nitration catalysts
-
Lanthanide(III) nosylates are novel, recyclable catalysts prepared from the noncorrosive and inexpensive p-nitrotoluenesulfonic acid and the corresponding lanthanide(III) oxide. With 5-10% catalyst loading, atom economic nitration of simple aromatic compounds was achieved in good to high yields.
- Parac-Vogt, Tatjana N.,Binnemans, Koen
-
p. 3137 - 3139
(2007/10/03)
-
- Electrophilic Aromatic Nitration Using a Mixed Catalyst of Lithium, Molybdenum, Ytterbium on Silica Gel
-
A novel mixed catalyst of LiClO4 (15% w/w), Yb(OPf)3 (15% w/w, Pf = perfluorooctanesulfonyl), MoO3 (15% w/w) on silica gel for electrophilic aromatic nitration reaction has been explored. The nitration reactions were accomplished by this mixed catalyst and nitric acid under solvent-free conditions. Moreover, the mixed catalyst can be easily recovered from the aqueous layer by heating in an oven and reused for the next nitration reaction.
- Shi, Min,Cui, Shi-Cong
-
p. 1329 - 1333
(2007/10/03)
-
- Mechanistic duality of the side-chain substitution in electrophilic aromatic nitration. Unexpected large difference in deuterium isotope effect k(H)/k(D) between the side-chain nitration and nitrooxylation of deuterated p-xylenes
-
A large difference in deuterium kinetic isotope effect observed between the side-chain nitration and nitrooxylation of deuterated p-xylenes, 1,4- (CH3)(CD3)C6H4 and 1,4-(CD3)2C6D4, suggests the operation of different mechanisms for these two types of side-chain substitution.
- Nonoyama, Nobuaki,Iwaya, Masao,Suzuki, Hitomi
-
p. 229 - 233
(2007/10/03)
-
- Reductive coupling of nitrobenzene or nitrobenzenes substituted on the nucleus to give the corresponding azobenzenes and azoxybenzenes by means of redox catalysts
-
Nitrobenzene or a nitrobenzene substituted on the nucleus is subjected to reductive coupling to give the corresponding azobenzene and azoxybenzene under heterogeneous catalysis with substantial avoidance of overreduction to aniline derivatives by means of a redox catalyst in its reduced or partly reduced form, the redox catalyst containing at least one active metal component capable of a change of oxidation state.
- -
-
-
- The first electron-donor-acceptor paracyclophanes with ferrocene NLO-phores: Synthesis, absorption and electrochemical properties
-
As potential nonlinear optical materials, 12-nitro-4,7-bis(2-ferrocenylvinyl)[2.2]paracyclophane (1) and 12-nitro-4,5,7,8-tetrakis(2-ferrocenylvinyl)[2.2]paracyclophane (2) have been synthesized by Pd-catalyzed coupling reactions of vinylferro-cene with the precursor cyclophanes 9 and 13, respectively. The absorption and electrochemical properties of 1 and 2 are also described. VCH Verlagsgesellschaft mbH.
- Kay, Kwang-Yol,Back, Yong Gu
-
p. 581 - 584
(2007/10/03)
-
- Lanthanide(III) triflates as recyclable catalysts for atom economic aromatic nitration
-
Lanthanide(III) triflates catalyse (1-10 mol%) the nitration of a range of simple aromatic compounds in good to excellent yield using stoichiometric quantities of 69% nitric acid; the only by-product is water and the catalyst can be readily recycled by simple evaporation.
- Waller, Francis J.,Barrett, Anthony G. M.,Braddock, D. Christopher,Ramprasad, Dorai
-
p. 613 - 614
(2007/10/03)
-
- Sulfuric acid on silica-gel: An inexpensive catalyst for aromatic nitration
-
Solid acidic catalysts made of sulfuric acid supported on silica-gel and their application to the nitration of aromatics with nitric acid and isopropyl nitrate are described. Substrates with very different levels of activation were investigated. Methods to overcome the poisoning produced by water and to tune the catalysts activity according to the reactivity of the substrate are outlined.
- Riego, Juan M.,Sedin, Zeno,Zaldivar, Jose M.,Marziano, Nunziata C.,Tortato, Claudio
-
p. 513 - 516
(2007/10/02)
-
- Iron(III)-catalysed nitration of non-activated and moderately activated arenes with nitrogen dioxide-molecular oxygen under neutral conditions
-
In the presence of molecular oxygen and a catalytic amount of tris(pentane-2,4-dionato)iron(III), non-activated and moderately activated arenes, which include alkylbenzenes, halogenobenzenes, phenolic ethers, naphthalene and derivatives, can be nitrated with nitrogen dioxide at ice-bath temperature or below to give the corresponding nitro derivatives in fair to good yields. An electron-transfer mechanism has been proposed, where an activated NO2-FeIII complex plays a key role in the cyclic process for converting arenes into nitroarenes.
- Suzuki, Hitomi,Yonezawa, Shuji,Nonoyama, Nobuaki,Mori, Tadashi
-
p. 2385 - 2389
(2007/10/03)
-
- Chemical pressure effect by selective deuteration in the molecular-based conductor, 2,5-dimethyl-N,N'-dicyano-p-benzoquinone immine-copper salt, (DMe-DCNQI)2Cu
-
The mixed-valence copper salt of DMe-DCNQI91, where DMe-DCNQI=2,5-dimethyl-N,N'-dicyano-p-benzoquinone diimine) is a molecular conductor whose electrical and magnetic properties are quite sensitive to pressure.We have performed selective deuteriation of the molecule 1.By control of the position and number of deuterium atoms, the low-pressure region (ca. 500 bar) in the pressure-temperature phase diagram of (1)2Cu was reproduced at ambient pressure.The equivalency of the deuteriation and pressure effects is explained from steric origins; 'contraction' aroused by the slightly shorter C-D bond (steric isotope effect) and 'constriction' by pressure.
- Aonuma, Shuji,Sawa, Hiroshi,Kato, Reizo
-
p. 1541 - 1550
(2007/10/02)
-
- Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation
-
Various polymethylbenzenes and anisoles are selectively nitrosated with the electrophilic nitrosonium salt NO(1+)BF4(1-) in good conversions and yields under mild conditions in which the conventional procedure (based on nitrile neutralization with strong acid) is ineffective.The reactivity patterns in acetonitrile deduced from the various time/conversions in Tables 2 and 3 indicate that aromatic nitrosation is distinctly different from those previously established for electrophilic aromatic nitration.The contrasting behavior of NO(1+) in aromatic nitrosation is ascribed to a rate-limiting deprotonation of the reversibly formed Wheland intermediate, which in the case of aromatic nitration with NO2(1+) occurs with no deuterium kinetic isotope effect.Aromatic nitroso derivatives (unlike the nitro counterpart) are excellent electron donors that are subject to a reversible one-electron oxidation at positive potentials significantly less than that of the parent polymethylbenzene or anisole.As a result, the series of nitrosobenzenes are also much better Broensted bases than the corresponding nitro derivatives, and this marked distinction, therefore, accounts for the large differentiation in the deprotonation rates of their respective conjugate acids (i.e.Wheland intermediates).
- Bosch, Eric,Kochi, Jay K.
-
p. 5573 - 5586
(2007/10/02)
-
- GAS-PHASE NITRATION OF AROMATIC COMPOUNDS AT ZEOLITES WITH NITROGEN DIOXIDE
-
The gas-phase nitration of benzene, toluene, ethylbenzene, chlorobenzene, and isomeric xylenes at various zeolites was studied. The dependence of the isomeric composition of the obtained products on the reaction conditions was investigated. A possible reaction mechanism is proposed.
- Salakhutdinov, N. F.,Ione, K. G.,Kobzar', E. A.,Malysheva, L. V.
-
p. 457 - 466
(2007/10/02)
-
- Aromatic nitration with electrophilic N-nitropyridinium cations. Transitory charge-transfer complexes as key intermediates
-
Electrophilic aromatic nitration of various arenes (ArH) is shown to be critically dependent on labile charge-transfer complexes derived from N-nitropyridinium cations. The electrophiles XPyNO2+, with X = CN, CO2CH3, Cl, H, CH3, and OCH3, form a highly graded series of electron acceptors that produce divers [ArH,XPyNO2+] complexes, with charge-transfer excitation energies (hvCT) spanning a range of almost 50 kcal mol-1. The latter underlie an equally broad spectrum of aromatic substrate selectivities from the different nitrating agents (XPyNO2+), but they all yield an isomeric product distribution from toluene that is singularly insensitive to the X substituent. The strong correlation of the nitration rates with the HOMO-LUMO gap in the [ArH,XPyNO2+] complex is presented (Scheme III) in the context of a stepwise process in which the charge-transfer activation process is cleanly decoupled from the product-determining step-as earlier defined by Olah's requirement of several discrete intermediates. This charge-transfer formulation thus provides a readily visualized as well as a unifying mechanistic basis for the striking comparison of XPyNO2+ with other nitrating agents, including the coordinatively unsaturated nitronium cation (NO2+BF4-), despite their highly differentiated reactivities.
- Kim,Lee,Kochi
-
p. 1756 - 1770
(2007/10/02)
-
- Reactions of 1,4-Dimethyl-4-nitro-cyclohexa-2,5-dien-1-yl Acetates with Nitrogen Dioxide; the Formation of Polynitro Cyclohexenyl Esters
-
Reactions of the epimeric 4-nitrocyclohexa-2,5-dienyl acetates (10) and (11) with nitrogen dioxide in acetic anhydride give closely similar mixtures of the nitro aromatic compounds (12)-(15), three polynitro nitrate esters (16)-(18), and two polynitro acetates (19) and (20).X-Ray crystal structure determinations are reported for compounds (16)-(18).
- Abell, Andrew D.,Hartshorn, Michael P.,Maclennan, Michael E.,Robinson, Ward T.,Wright, Graeme J.
-
-
- SYNTHESIS OF FLUOROMETHOXYTHRIN AND ITS INSECTICIDAL ACTIVITY
-
Fluoromethoxythrin is a kind of pyrethroid.It was synthesized by an eight-step synthesis.The biological activity tests indicated that it has higher insectizidal activity against mosquitoes (larvae), houseflies and German cockroaches than the corresponding methoxythrin.
- Xinzhuo Zou,Keqan Gu
-
p. 507 - 513
(2007/10/02)
-
- Oxidative Aromatic Nitration with Charge-Transfer Complexes of Arenes and Nitrosonium Salts
-
Brightly colored solutions are obtained immediately upon the exposure of various arenes (ArH) to nitrosonium (NO+) salts.The colors arise from the charge-transfer transitions of 1:1 complexes +> that are reversibly formed as persistent intermediates.However the yellow-red charge-transfer (CT) colors are readily bleached by dioxygen, and the corresponding nitroarenes (ArNO2) can be isolated in excellent yields from acetonitrile solutions.Such an oxidative aromatic nitration of aromatic donors proceeds via the initial autooxidation of the charge-transfer complex.The collapse of the resulting radical ion pair .+,NO2> to the ?-adduct, followed by the loss of proton, affords ArNO2.Direct evidence for electron transfer in the initial step when anthracene is treated with NO+PF6- stems for the isolation of (a) the anthracene ion radical salt .+PF6-> along with nitric oxide in dichloromethane solution and (b) the formation of 9-nitroanthracene (admixed with anthraquinone) in the more polar acetonitrile.The aromatic products (and isomer distribution) from oxidative aromatic nitration are highly reminiscent of those from electrophilic aromatic nitration.The possibility of common reactive intermediates in these two distinctive pathways for aromatic nitration is discussed.
- Kim, E. K.,Kochi, J. K.
-
p. 1692 - 1702
(2007/10/02)
-
- Reactions of the 1-hydroxy-1,4-dimethylcyclohexadienyl cation, an intermediate in the solvolysis of 1,4-dimethyl-4-nitrocyclohexa-2,5-dien-1-ol
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Solvolysis of 1,4-dimethyl-4-nitrocyclohexa-2,5-dien-1-ol in mixed aqueous organic solvents gives the diastereomers of 1,4-dimethylcyclohexa-2,5-dien-1,4-diol, 1,4-dimethylcyclohexa-3,5-diene-1,2-diol, 2-nitro-p-xylene, 2,4-dimethylphenol (all derived from the title cation, itself formed by ionization of the nitro group as nitrite), and 2,5-dimethylphenol.In aqueous methanol the diastereomers of 4-methoxy-1,4-dimethylcyclohexa-2,5-dienol are also obtained.Significant yields of 2,5-dimethylphenol are only obtained on the acid-catalyzed further reaction of the dienediol (or the methoxydienol) and involve the intermediate formation of 1,4-dimethylcyclohexa-3,5-diene-1,2-diol.In the absence of added base the acid released in the solvolysis catalyses this reaction and leads to the aromatization of the dienes.
- Fischer, Alfred,Henderson, George N.,Smyth, Trevor A.
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p. 1093 - 1101
(2007/10/02)
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- Steric Influences on Spin-Lattice Relaxation Rates of Methyl Protons in Substituted Aromatic Molecules
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Proton spin-lattice relaxation rates (R1 values) have been measured at 400 MHz for a series of substituted aromatic compounds to determine the steric effects of ortho substituents on the R1 values of the methyl groups.These values have been interpreted on the basis of differences in the barriers to methyl group rotation caused by the substituent, resulting in changes in the contributions from the dipolar and the spin-rotation relaxation mechanisms.A significant dynamic range of methyl R1 values has been observed, showing that these measurements are sensitive to the steric environment.
- Chazin, Walter J.,Colebrook, Lawrence D.
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p. 597 - 604
(2007/10/02)
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- Reactions of Cerium(IV) Ammonium Nitrate with Aromatic Compounds in Acetonitrile. Part 2. Nitration; Comparison with Reactions of Nitric acid
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The nitration of benzene and a number of alkylbenzenes by cerium(IV) ammonium nitrate in acetonitrile shows the same intra- and inter-molecular selectivity as nitration with nitric acid under the same conditions but the extent of the other products formed in the two sets of reactions is very different.Nitration by cerium(IV) ammonium nitrate (but not side-chain substitution) is suppressed by the addition of water.The results suggest that these nitration reactions by cerium(IV) ammonium nitrate occur through the intermediate formation of a nitronium ion from the cerium(IV) complex but the order with recpect to the aromatic compound shows that this nitronium ion must then be formed in the presence of the aromatic substrate as a 'spectator'.The relative reactivities with respect to benzene in the nitration of anisole and naphthalene are much greater than those observed in nitration by nitric acid and, with both, the isomer proportions are also anomalous.
- Dinctuerk, Suphi,Ridd, John H.
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p. 965 - 970
(2007/10/02)
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- Ipso Nitration. Solvolytic Behavior of 1,4-Dimethyl-4-nitrohexadienyl Acetate and 1,4-Dimethyl-4-nitrocyclohexadienol
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The solvolytic rearomatizations of the E and Z isomers of 1,4-dimethyl-4-nitrocyclohexadienyl acetate (1) have been examined in aqueous ethanol and in sulfuric acid solutions.Solvolysis of 1 in aqueous ethanol involves the elimination of nitrous acid and the migration of the acetoxyl group to yield 2,5-dimethylphenyl acetate.The kinetic behavior of this solvolytic reaction parallels that of the secondary adduct 4-nitro-3,4,5-trimethylcyclohexadienyl acetate (2).No kinetic isotope effects were detected when 1,4-dimethyl-4-nitrocyclohexadienyl-2,3,5,6-d4 acetate (1-d4) or 1,4-dimethyl-4-nitrocyclohexadienyl-Me-d6 (1-d6) were used as substrates.The collected data suggest a rate-limiting loss of nitrile ion from 1 followed by migration of the acetoxyl group and proton loss.The behavior of Z and E isomers of 1,4-dimethyl-4-nitrocyclohexadienol (3) in aqueous ethanol differs from that of 1 in several ways.The major product of solvolysis is 2,4-dimethylphenol.The rates of solvolysis of the stereoisomers of 3 do not differ appreciably one from another, and the spectral yield is only 30-40percent of that anticipated.These differences are taken to reflect a rate-limiting migration in the solvolysis of 3 rather than a rate-limiting loss of nitrate ion.Solvolysis of 1 in greater than 77percent sulfuric acid gives 1,4-dimethyl-2-nitrobenzene in quantitative yield.The yield of nitro aromatic falls off smoothly as the acid concentration is lowered toward 50percent.Within the 70-50percent acid range, the yield of side-chain substitution products appears to increase, hold roughly constant, and then decrease.Larger yields of nitro aromatic and smaller yields of side-chain substitution product are found when 1-d6 is used as a reactant.The solvolyses in strong acids are discussed in terms of re-formation of the ipso ion and subsequent partitioning.
- Geppert, J. T.,Johnson, M. W.,Myhre, P. C.,Woods, S. P.
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p. 2057 - 2062
(2007/10/02)
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- Gas-Phase Hydroxyl Radical Reactions. Products and Pathways for the Reaction of OH with Aromatic Hydrocarbons
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The reactions of OH with benzene, toluene, 1,4-dimethylbenzene, and 1,3,5-trimethylbenzene have been investigated in a discharge flow system at total pressures of 6-12 torr.In the presence of NO, NO2, and O2 the intermediate radicals are converted quantitatively to stable products from which two major reaction pathways are identified.Abstractionof a hydrogen atom from the methyl group by OH leads primarily to the corresponding aldehyde, and addition to the aromatic ring by OH gives primarily the corresponding phenols.Nitro substitution of the aromatics via the OH adduct competes with phenol formation; however, the amount depends on the ratio of NO2/O2.In the case for toluene, the ratio of rate constants, kNO2/kO2, for the two processes is (4+/- 2) X 103.The isomer distributions for OH addition to toluene were determined to be 0.806 +/- 0.022 ortho, 0.051 +/- 0.009 meta, 0.143 +/- 0.019 para, and 1) relative to total reaction (k1 + k2) are 0.15 +/- 0.02 for toluene, 0.15 +/- 0.02 for 1,4-dimethylbenzene, and 0.021 +/- 0.006 for 1,3,5-trimethylbenzene.
- Kenley, Richard A.,Davenport, John E.,Hendry, Dale G.
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p. 2740 - 2746
(2007/10/02)
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- Aromatic Substitution. 48. Boron Trifluoride Catalyzed Nitration of Aromatics with Silver Nitrate in Acetonitrile Solution
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Benzene, alkylbenzenes, halobenzenes, and anisole were nitrated with silver nitrate/boron trifluoride in acetonitrile solution.Correlation of competitive rates with ?- and ?-complex stabilities indicated that the transition state of highest energy lies relatively early on the reaction coordinate.Data indicate that nitrations occur via a polarized complex of the nitrating agent, with the catalyst undergoing nucleophilic displacement by the aromatic substrate.
- Olah, George A.,Fung, Alexander P.,Narang, Subhash C.,Olah, Judith A.
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p. 3533 - 3537
(2007/10/02)
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