- Rate constant ratios in the consecutive chlorination of liquid-phase p-xylene with Cl2 and an iron(III) chloride catalyst
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Given that p-xylene is an important chemical feedstock for many final products in the market from pesticides, pharmaceuticals, peroxides to dyes, its chlorinated derivatives are of interest in the chemical industry. In this paper, the rate constant ratios of the consecutive chlorination of p-xylene at 70°C in a gas–liquid semibatch reactor using molecular chlorine and iron(III) chloride as a catalyst was investigated up to the fourth successive reaction (tetrachloro-p-xylene production). The ratios were determined with both mathematical expressions and a graphical method proposed recently in the literature by use of the maxima of the successive products. The ratios found for monochloro-p-xylene (2-chloro-p-xylene), dichloro-p-xylene (the sum of 2,3-dichloro-p-xylene and 2,5-dichloro-p-xylene), trichloro-p-xylene (2,3,5-trichloro-p-xylene), and tetrachloro-p-xylene (2,3,5,6-tetrachloro-p-xylene) are k2/k1=?0.295, k3/k1=?0.0826, and k4/k1=?0.00383. The ratio of the dichlo-isomers produced was also determined as 2.12 in favor of 2,5-dichloro-p-xylene, which is reasonable since 2,3-dichloro-p-xylene is highly hindered by the adjacent groups on the aromatic nucleus. The existing knowledge found in the literature on the rate constant ratios of consecutive reactions was also extended in this paper with a new mathematical expression for the determination of the third stage product peak concentration. The standard uncertainties of the rate constant ratios, the standard deviation of the means, as well as the expanded uncertainties of the means, were calculated. Finally, the propagation of uncertainties for the trichloro-p-xylene was estimated using the partial derivatives of this product for each of the rate constants.
- Rigas, Fotis P.
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- Triptycenyl Sulfide: A Practical and Active Catalyst for Electrophilic Aromatic Halogenation Using N-Halosuccinimides
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A Lewis base catalyst Trip-SMe (Trip = triptycenyl) for electrophilic aromatic halogenation using N-halosuccinimides (NXS) is introduced. In the presence of an appropriate activator (as a noncoordinating-anion source), a series of unactivated aromatic compounds were halogenated at ambient temperature using NXS. This catalytic system was applicable to transformations that are currently unachievable except for the use of Br2 or Cl2: e.g., multihalogenation of naphthalene, regioselective bromination of BINOL, etc. Controlled experiments revealed that the triptycenyl substituent exerts a crucial role for the catalytic activity, and kinetic experiments implied the occurrence of a sulfonium salt [Trip-S(Me)Br][SbF6] as an active species. Compared to simple dialkyl sulfides, Trip-SMe exhibited a significant charge-separated ion pair character within the halonium complex whose structural information was obtained by the single-crystal X-ray analysis. A preliminary computational study disclosed that the πsystem of the triptycenyl functionality is a key motif to consolidate the enhancement of electrophilicity.
- Nishii, Yuji,Ikeda, Mitsuhiro,Hayashi, Yoshihiro,Kawauchi, Susumu,Miura, Masahiro
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p. 1621 - 1629
(2020/02/04)
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- Sulfur(VI) fluoride compounds and methods for the preparation thereof
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This application describes a compound represented by Formula (I): (I) wherein: Y is a biologically active organic core group comprising one or more of an aryl group, a heteroaryl aryl group, a nonaromatic hydrocarbyl group, and a nonaromatic heterocyclic group, to which Z is covalently bonded; n is 1, 2, 3, 4 or 5; m is 1 or 2; Z is O, NR, or N; X1 is a covalent bond or —CH2CH2—, X2 is O or NR; and R comprises H or a substituted or unsubstituted group selected from an aryl group, a heteroaryl aryl group, a nonaromatic hydrocarbyl group, and a nonaromatic heterocyclic group. Methods of preparing the compounds, methods of using the compounds, and pharmaceutical compositions comprising the compounds are described as well.
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- Photocatalytic activation of N-chloro compounds for the chlorination of arenes
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Photoredox catalysis activates N-chloramines and N-chloro-succinimide (NCS) for the electrophilic chlorination of arenes. The photooxidation of the nitrogen atom to a radical cation induces a positive polarization on the chlorine atom, which results in a higher reactivity in electrophilic aromatic chlorination reactions.
- Hering, Thea,K?nig, Burkhard
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p. 7821 - 7825
(2016/11/16)
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- Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
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Aryl chlorides and bromides are formed from arenes in a ball mill using KHSO5 and NaX (X = Cl, Br) as oxidant and halogen source, respectively. Investigation of the reaction parameters identified operating frequency, milling time, and the number of milling balls as the main influencing variables, as these determine the amount of energy provided to the reaction system. Assessment of liquid-assisted grinding conditions revealed, that the addition of solvents has no advantageous effect in this special case. Preferably activated arenes are halogenated, whereby bromination afforded higher product yields than chlorination. Most often reactions are regio- and chemoselective, since p-substitution was preferred and concurring side-chain oxidation of alkylated arenes by KHSO5 was not observed. The Royal Society of Chemistry.
- Schmidt, Robert,Stolle, Achim,Ondruschka, Bernd
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p. 1673 - 1679
(2013/02/22)
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- Photochemical dehalogenation mediated by macrocyclic nickel(II) complexes
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A new photochemical dehalogenation system mediated by macrocyclic nickel(II) complexes was developed. Using this system, which consists of a macrocyclic nickel(II) complex catalyst, triethanolamine (TEOA) as a sacrificial reductant, and the ruthenium complex [Ru(bpy)3](ClO 4)2 as a photosensitizer, catalytic debromination of 1-bromo-4-t-butylbenzene in acetonitrile was effectively carried out. The catalytic capabilities of various macrocyclic nickel(II) complexes in debromination reactions were also elucidated.
- Mochizuki, Katsura,Suzuki, Mana
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experimental part
p. 902 - 905
(2011/06/23)
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- Microwave assisted solid additive effects in simple dry chlorination reactions with n-chlorosuccinimide
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Solid additives participate in the dry microwave assisted chlorination reaction of N-chlorosuccinimide with the xylenes affecting both yields and chemoselectivities. Total yields can be increased up to nine times for simple alkylaromatics and chemoselectivities can be altered according to the desired ring or α-side chlorination product by choosing the appropriate additive. We believe that in these reactions the solid additives play a very important role by increasing yields and affecting chemoselectivities, as well as behaving as microwave energy absorbers that consequently aid the transfer of heat to the active reagents.
- Bucos, Madalina,Villalonga-Barber, Carolina,Micha-Screttas, Maria,Steele, Barry R.,Screttas, Constantinos G.,Heropoulos, Georgios A.
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experimental part
p. 2061 - 2065
(2010/04/26)
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- Phosphonium nitrate ionic liquid catalysed electrophilic aromatic oxychlorination
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Trioctylmethylphosphonium nitrate (P8,8,8,1NO3), an ionic liquid made via a green synthesis, catalyses electrophilic aromatic chlorination of arenes with HCl and air at 80 °C. The aromatic oxychlorination is truly catalytic in nitrate, proceeds without added solvents, and uses atmospheric oxygen as oxidant. The extent of chlorination can be controlled to yield selectively mono or dichlorinated products, and the ionic liquid catalyst can be recycled. Dependence of the chlorination rate on HCl and nitrate concentrations as well as on the rate of re-oxidation of the nitrogen intermediates by air, allowed us to propose a reaction mechanism.
- Noe, Marco,Perosa, Alvise,Selva, Maurizio,Zambelli, Luca
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experimental part
p. 1654 - 1660
(2010/12/19)
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- Regiospecific chlorination of xylenes using K-10 montmorrillonite clay
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Regiospecific chlorination of xylenes has been developed by employing NCS as a reagent and K-10 montmorrillonite clay as a solid support. Copyright Taylor & Francis Group, LLC.
- Thirumamagal,Narayanasamy, Sureshbabu,Venkatesan
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scheme or table
p. 2820 - 2825
(2009/05/07)
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- Chlorination of aromatics with trichloroisocyanuric acid (TCICA) in bronsted-acidic imidazolium ionic liquid [BMIM(SO3H)][OTf]: An economical, green protocol for the synthesis of chloroarenes
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A survey study on electrophilic chlorination of aromatics with trichloroisocyanuric acid (TCICA) in Bronsted-acidic imidazolium ionic liquid [BMIM(SO3H)][OTf] is reported. The reactions are performed under very mild conditions (at ～50°C) and give good to excellent yields, depending on the substrates. Chemoselectivity for mono- v. dichlorination can be tuned by changing the arene-to-TCICA ratio and the reaction time. The survey study and competitive experiments suggest that triprotonated/protosolvated TCICA is a selective/moderately reactive transfer-chlorination electrophile. Density functional theory was used as guide to obtain further insight into the nature of the chlorination electrophile and the transfer-chlorination step. CSIRO 2007.
- Hubbard, Abigail,Okazaki, Takao,Laali, Kenneth K.
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p. 923 - 927
(2008/03/17)
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- Grindstone chemistry: (Diacetoxyiodo)benzene-mediated oxidative nuclear halogenation of arenes using NaCl, NaBr or I2
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A technique of "Grindstone chemistry" is applied to the solvent-free halogenation of arenes with NaCl, NaBr or I2 using (diacetoxyiodo)benzene as the oxidant. Improved yields and higher purities of the products are observed compared with those from established methods.
- Karade,Tiwari,Huple,Siddiqui
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p. 366 - 368
(2007/10/03)
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- PROCESS FOR HALOGENATION OF BENZENE AND BENZENE DERIVATIVES
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In a process of halogenation of benzene or benzene derivatives, di-substituted halobenzene derivatives having para-aromatic compounds or tri-substituted halobenzene derivatives having 1,2,4-substituted aromatic compounds are selectively produced. In halogenation of benzene or benzene derivatives, a fluorine-containing zeolite catalyst such as L-type zeolite, or a zeolite catalyst having the crystal size of at most 100 nm is used. The reaction is preferably effected in the presence of a solvent, and the solvent is preferably a halogenated compound.
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Page/Page column 23-24
(2008/06/13)
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- Electrophilic aromatic chlorination and haloperoxidation of chloride catalyzed by polyfluorinated alcohols: A new manifestation of template catalysis
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We have demonstrated that a polyfluorinated alcohol, 2,2,2-trifluoroethanol, solvent enables haloperoxidase type activity and the oxychlorination of arenes (benzene and its alkylated derivatives) without a metal catalyst. The polyfluorinated alcohol has a dual function; it catalyzes electrophilic chlorination of less reactive arenes by several orders of magnitude and oxidation of chloride at lower H+ concentrations. DFT calculations show that a complementary charge template in the transition state explains the catalysis of the electrophilic chlorination. Copyright
- Ben-Daniel, Revital,De Visser, Samuel P.,Shaik, Sason,Neumann, Ronny
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p. 12116 - 12117
(2007/10/03)
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- A novel and efficient ceric ammonium nitrate catalyzed oxidative nuclear chlorination of activated aromatic compounds by acetyl chloride
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A mild and efficient oxidative chlorination of activated aromatic compounds have been achieved in excellent yields using acetyl chloride in the presence of a catalytic amount of ceric ammonium nitrate at room temperature. However, chlorination failed to occur with deactivated aromatic rings.
- Roy, Subhas Chandra,Rana, Kalyan Kumar,Guin, Chandrani,Banerjee, Biplab
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p. 221 - 222
(2007/10/03)
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- Novel process for generating useful electrophiles from common anions using Selectfluor fluorination agent
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In the present work, the electrophile equivalents C1+, Br+, SCN+, and NO2+ are generated from their respective sodium, potassium, and in some cases ammonium salts (M+X-) by reaction with Selectfluor electrophilic fluorination agent in acetonitrile solution at room temperature. These generated electrophilic species subsequently react in situ with a variety of aromatic substrates containing one or more substituent groups including H, F, C1, CH3, COOH, C(O)CH3, NO2, and OR′ and NR′R″ where R′ and R″ are H or CH3. The resulting substitution products are, in most cases, isolable as pure compounds in high yield. Variations in the process include the use of other anions, electrophilic fluorination agents, and solvents.
- Syvret, Robert G.,Butt, Kathleen M.,Nguyen, Tung P.,Bulleck, Victoria L.,Rieth, Ryan D.
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p. 4487 - 4493
(2007/10/03)
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- Peroxide Salts as Reagents in Oxidative Halogenation of Aromatic Compounds
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Chloromesitylene, chloro-p-xylene, and 1-bromonaphthalene are formed in 78, 79, and 86percent yield, respectively, under the action of the halogenating system hydrogen peroxide-hydrohalic acid-AcOH.The following aryl halides are also formed in high yields in this halogenating system: 2-bromothiophene (89 - 92percent) upon bromonation of thiophene; chlorobenzene (77 - 79percent) and iodobenzene (79 - 81percent) upon chlorination and iodination of benzene.
- Rudakova, N. I.,Erykalov, Yu. G.,Zharikova, S. M.,Dmitrieva, E. V.,Mataradze, M. S.
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p. 271 - 272
(2007/10/03)
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- Ring Halogenations of Polyalkylbenzenes by Ionic Halides and Koser's Reagent
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Ring chlorinations of polyalkylbenzenes such as mesitylene have been carried out at room temperature with LiCl or NaCl and stoichiometric amounts of Koser's reagent.Solvent range from water to methylene chloride.The procedures were extended to bromination and iodination.
- Bovonsombat, Pakorn,Djuardi, Elsa,Nelis, Edward Mc
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p. 2841 - 2844
(2007/10/02)
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- Kinetics of nuclear chlorination of toluene and some substituted toluenes by trichloroisocyanuric acid
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Nuclear chlorination of toluene and substituted toluenes by trichloroisocyanuric acid is first order each in and .The observed second order rate constants increase with increase in +> in solvent mixtures containing less than 50percent HOAc.The k2 values increase with an increase in the proportion of HOAc, reach maximum at 50percent HOAc above which the rate constants have a diminishing trend.At higher proportion of HOAc, the rate constants are insensitive to change in .Added Cl- ions enhance the rate.Based on the observed results a plausible mechanism has been proposed which envisages a positive ion dipole reaction between H+2OCl generated from hydrolysis of TCICA and the substrate molecules at low proportions of HOAc.At high proportion of HOAc, chlorine acetate has been suggested to be the electrophile.Molecular chlorine as well as H2O+Cl are the chlorinating species in the presence of Cl- ions.The Hammett plot is linear with a ρ value -5.55.The activation parameters have been computed.
- Panda, H. P.,Sahoo, K. K.
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p. 717 - 720
(2007/10/02)
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- REACTIVITY OF 3,6-DIMETHOXY-3,6-DIMETHYLCYCLOHEXA-1,4-DIENE: NUCLEAR VERSUS BENZYLIC NUCLEOPHILIC SUBSTITUTION
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The treatment of cis/trans-3,6-dimethoxy-3,6-dimethylcyclohexa-1,4-diene (ca. 1/1 mixture; easily prepared electrochemically in multigram scale from p-xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a trasposition reaction.The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-dimethylphenol 12, and with hydrogen chloride a mixture of 2- and α-chloro-p-xylene (13, 14) is isolated.Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols,thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/ and benzylic substitution on p-xylene (15 - 20).The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner.In all cases the mixtures of isomers are separated by column chromatography.The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving p-xylene.A probable mechanism is proposed for the studied reactions.
- Alonso, Francisco,Barba, Isidoro,Yus, Miguel
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p. 2069 - 2080
(2007/10/02)
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- Versatility of Zeolites as Catalysts for Ring or Side-Chain Aromatic Chlorinations by Sulfuryl Chloride
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Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2.It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination.Zeolite ZF520 is the choice catalyst for the former, because of its high Broensted acidity.Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be reused many times with no loss in activity.Both reaction modes, the ionic (ring chlorination)and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid.The effects of various experimental factors - such as the nature of the solvent, the reaction time and temperature, the Broensted acidity of the solid support, the presence of radical inhibitors, and the quantity of catalysts - were investigated.The procedures resulting from this study are very easy to implement in practice and are quite effective.
- Delaude, Lionel,Laszlo, Pierre
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p. 5260 - 5269
(2007/10/02)
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- RING CHLORINATION OF BENZENOID COMPOUNDS USING CALCIUM HYPOCHLORITE
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Chlorination of activated benzenoid rings is efficiently effected at 0 deg C in aqueous acetone/HOAc using calcium hypochlorite as the chlorinating agent.Good to excellent yields of the chlorinated products are obtained.
- Nwaukwa, Stephen O.,Keehn, Philip M.
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p. 799 - 804
(2007/10/02)
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- Halogenation Using Quaternary Ammonium Polyhalides. XIX. Aromatic Chlorination of Arenes with Benzyltrimethylammonium Tetrachloroiodate
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The reaction of arenes with a calculated amount of benzyltrimethylammonium tetrachloroiodate in acetic acid at room temperature or at 70 deg C gave nuclear chloro-substituted arenes in fairly good yields.
- Kajigaeshi, Shoji,Ueda, Yasuhiro,Fujisaki, Shizuo,Kakinami, Takaaki
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p. 2096 - 2098
(2007/10/02)
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- Lewis Acid Catalyzed Sulphenylation of Methylbenzene by p-Chlorobenzenesulphenyl Chloride
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The Lewis acid catalyzed reactions of benzene and several methylbenzenes with p-chlorobenzenesulphenyl chloride are reported.The products include sulphenylated arenes - p-chlorophenyl aryl sulphides, bis(p-chlorophenylthio)arenes, chloro(p-chlorophenylthio)arenes - as well as chlorinated arenes and bis(p-chlorophenyl)disulphides.The disulphide: combined sulphenylation products ratio for each arene, e.g. 27:73 (for benzene) and 12:86 (for mesitylene), shows only a small variation when compared to the large differences in reactivity of the arenes towards electrophilic reagents.
- Grant, Douglas W.,Hogg, Donald R.,Wardell, James L.
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p. 3123 - 3143
(2007/10/02)
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