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Solvent-free isomerization of 3-carene to 2-carene using Na/o-chlorotoluene catalyst in trans-isolimonene production
Trans-isolimonene is one of the important compound in drugs development. This compound can be made by isomerization of inexpensive 3-carene via 2-carene using Na/o-chlorotoluene catalyst in xylene. The existence of xylene as a solvent requires a further separation process that can reduce the efficiency when applied in the bulk industry. The isomerization of 3-carene to 2-carene has been studied in solvent free reaction compared by isomerization without xylene solvent. The result showed that the isomerization can also occur in solvent-free condition. Solventfree isomerization gave 27.72% of conversion and 83.27% of selectivity while isomerization with solvent gave 23.59% of conversion and 86.87% of selectivity.
Julianto, Tatang Shabur,Jumina,Jojo, Hardjono Sastrohamid,Mustofa
p. 3107 - 3111
(2017)
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Gas phase toluene isopropylation over high silica mordenite
Mordenite (HM) catalysts with three different Si/Al ratios were compared for their activity and selectivities in gas phase toluene isopropylation with isopropanol. Catalyst with Si/Al ratio 44·9 offered better cumene selectivity, hence, it was chosen for detailed kinetic investigations. The influence of various process parameters like temperature, time-on-stream, weight hourly space velocity (WHSV), reactant mole ratio on this catalyst activity are discussed. The cymene selectivity was found to increase with reaction temperature and passed through a maximum at 473 K. The deactivation with time-onstream is almost negligible. Lower isopropyl alcohol concentration in the feed improved cymene selectivity. The conversion and selectivity to cymenes were compared with those of the large pore beta catalyst. The rate constant and activation energy were found to be 7·34 m3/kg h and 41·84 kJ/mol, respectively using homogeneous kinetic model. Indian Academy of Sciences.
Upadhyayula, Sreedevi
p. 613 - 619
(2010)
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Alkylation of Toluene with Isopropanol on Lantanum Modified ZSM-5 Zeolite
Abstract: The effect of lanthanum concentration on the physicochemical and catalyticproperties of HZSM-5 zeolite in a reaction of toluene alkylation withisopropanol was studied in a temperature range of 250–350°C. Based on the dataobtained by X-ray diffraction analysis, low-temperature nitrogen adsorption (BETmethod), and IR spectroscopy, it was shown that an increase in lanthanumconcentration in HZSM-5 from 1.0 wt % to 7.0 wt % reduces both the specificsurface area and the pore volume of the zeolite despite the retention of itscrystalline structure. This also results in redistribution of acid sites,specifically decreases the concentration of strong Br?nsted acid sites (B) andincreases that of moderate Lewis acid sites (L), thus decreasing the B/L ratiofrom 3.53 to 0.20. All these occurrences have a crucial effect on theselectivity of reaction products and, in particular, on the p-isopropyl toluene (4-IPT) selectivity. Maximumselectivity, making up 72.4%, is achieved by a zeolite containing 5.0 wt %lanthanum at a B/L ratio of 0.25.
Abdullaeva,Voskressenskii,Akhmedova,Mamedov
p. 190 - 197
(2020/12/17)

Novel approach towards Al-rich AFI for catalytic application
A new germanosilicate structural analogue of AFI zeolite (Ge-AFI) was hydrothermally synthesized. One- and two-step alumination of the Ge-AFI zeolites were used to modify their structure and acidic properties traced using XRD, N2 adsorption, ICP-OES, 27Al NMR, and FTIR spectroscopy. Two-step aluminated sample (deGe-Al-AFI) provided a higher Al content, stronger acid sites and a higher micropore volume than one-step aluminated sample (Al-AFI). Extensive evaluation of the catalytic performance of these AFI zeolites compared with reference conventional zeolite catalysts for alkylation of toluene with isopropyl alcohol showed that deGe-Al-AFI exhibited relatively high toluene conversion and selectivity to valuable p-cymene due to the optimized textural and acidic properties.
Zhou, Yong,?ilková, Nadě?da,Shamzhy, Mariya,Avadhut, Yamini,Hartmann, Martin,?ejka, Ji?í,Opanasenko, Maksym
p. 62 - 68
(2019/04/01)

Iron-Catalyzed Isopropylation of Electron-Deficient Aryl and Heteroaryl Chlorides
Traditional methods for the preparation of secondary alkyl-substituted aryl and heteroaryl chlorides challenge both selectivity and functional group tolerance. This contribution describes the use of statistical design of experiments to develop an effective procedure for the preparation of isopropyl-substituted (hetero)arenes with minimal isopropyl to n-propyl isomerization. The reaction tolerates electronically diverse aryl chloride coupling partners, with excellent conversion observed for strongly electron-deficient aromatic rings, such as esters and amides. Electron-rich systems, including methyl- and methoxy-substituted aryl chlorides, were found to be less reactive. Furthermore, the reaction was found to be most successful when heteroaryl chlorides were submitted to the cross-coupling protocol. By mapping substituent effects on reaction selectivity, we were able to show that electron-deficient aryl chlorides are essential for efficient coupling, and use electronic structure calculations to predict the likelihood of successful coupling through the estimation of the electron affinity of each aryl chloride. Moderate isolated yields were achieved with selected aryl chlorides, and moderate to good isolated yields were obtained for all the heteroaryl chlorides coupled. Excellent selectivity was observed when a 2,6-dichloroquinoline was used, allowing mono-substitution on a challenging substrate. (Figure presented.).
Sanderson, James N.,Dominey, Andrew P.,Percy, Jonathan M.
p. 1007 - 1017
(2017/03/27)

Heterogeneous Catalytic Hydroarylation of Olefins at a Nanoscopic Aluminum Chlorofluoride
We report on hydroarylation reactions of arenes with olefins under very mild conditions catalyzed heterogeneously by aluminum chlorofluoride (ACF; AlClxF3?x, x≈0.05–0.25). The reactions of benzene and toluene with ethylene or propylene proceed with high conversions to afford various alkylated arenes. For cyclohexene and 1-hexene, the reactions require higher temperatures and the conversions are lower. ACF also catalyzes the hydroarylation of 1,3,5-trifluorobenzene and pentafluorobenzene with ethylene and propylene. The alkylations of arenes with non-fluorinated olefins resemble typical Friedel–Crafts chemistry to give rise to Markovnikov regioselectivity. The reaction of CF3CH=CH2 with benzene proceeds with anti-Markovnikov regioselectivity to give the fluorinated olefin PhCHCH=CF2 and the alkylation product PhCH2CH2CF3 as products of C?F and C?H activation.
Calvo, Beatriz,Wuttke, Jan,Braun, Thomas,Kemnitz, Erhard
p. 1945 - 1950
(2016/07/06)

Production of p -cymene from crude sulphate turpentine with commercial zeolite catalyst using a continuous fixed bed reactor
Crude sulphate turpentine (CST), containing -pinene, 3-carene, other terpene isomers, and organic sulphur compounds, was used as feedstock in the production of cymenes with commercial zeolite catalysts. The catalysts used were not sensitive to sulphur, and the desulphurisation step was not needed prior to cymene synthesis. The experiments were performed in a continuous fixed bed reactor. Promising results were obtained after initial optimization at temperatures close to 300 °C with faujasite Y zeolite under 5 bar N2 pressure. Cymenes were produced with 54% yields from model compound -pinene and with 28% yields from CST. The mechanistic route of the reaction can be divided into three steps: (1) ring opening, (2) rearrangement, and (3) dehydrogenation. The final step in the formation of p-cymene can occur via dehydrogenation or disproportion; here the effect of reaction conditions and catalyst plays a crucial role.
Linnekoski, Juha A.,Asikainen, Martta,Heikkinen, Harri,Kaila, Reetta K.,R?s?nen, Jari,Laitinen, Antero,Harlin, Ali
p. 1468 - 1475
(2015/02/19)

Polar reactions of acyclic conjugated bisallenes
The chemical behaviour of various alkyl-substituted, acyclic conjugated bisallenes in reactions involving polar intermediates and/or transition states has been investigated on a broad scale for the first time. The reactions studied include lithiation, reaction of the thus formed organolithium salts with various electrophiles (among others, allyl bromide, DMF and acetone), oxidation to cyclopentenones and epoxides, hydrohalogenation (HCl, HBr addition), halogenation (Br2 and I2 addition), and [2 + 2] cycloaddition with chlorosulfonyl isocyanate. The resulting adducts were fully characterized by spectroscopic and analytical methods; they constitute interesting substrates for further organic transformations.
Stamm, Reiner,Hopf, Henning
supporting information
p. 36 - 48
(2013/03/13)

Facile fabrication of aluminum-promoted vanadium phosphate: A highly active heterogeneous catalyst for isopropylation of toluene to cymene
Vanadium phosphate is well known as a heterogeneous catalyst in gas phase oxidation reactions. To date, there has been little interest in carrying out liquid-phase reactions with vanadium phosphate as catalyst. Herein, we report the catalytic activity of vanadium phosphate and aluminum-promoted vanadium phosphate toward liquid-phase isopropylation of toluene to cymene. The catalysts were unambiguously characterized by X-ray diffraction, N2 adsorption-desorption, FT-IR technique, UV-vis DRS, and FE-SEM. The total acid sites were estimated by an NH3 TPD analyzer. XPS was used as a powerful tool to know the electronic environment of the catalysts. The optimization of the reaction was carried out by varying temperature from 75 to 150 °C and molar ratio (toluene: isopropanol) from 1:1-1:3. Under optimum reaction conditions, 5 wt.% aluminum-promoted vanadium phosphate showed 90% conversion with 85% selectivity to p-cymene.
Behera, Gobinda Chandra,Parida,Das
scheme or table
p. 190 - 198
(2012/06/01)

Design and performance of supported Lewis acid catalysts derived from metal contaminated biomass for Friedel-Crafts alkylation and acylation
The main goal of this work was to prove the interest of metal hyperaccumulator plants in supported Lewis acid catalysis. Friedel-Crafts alkylation and acylation reveal the great catalytic activity of different plant extracts. This approach is a green solution with chemical benefits including high yield, excellent regioselectivity, small amounts of catalyst, mild conditions and concrete perspectives towards the depletion of mineral resources. The results also constitute an incentive for the development of phytoextraction programs on metal-bearing soils.
Losfeld, Guillaume,Escande, Vincent,Vidal De La Blache, Paul,L'Huillier, Laurent,Grison, Claude
experimental part
p. 111 - 116
(2012/09/08)

Selective reduction of biomass by hydriodic acid and its in situ regeneration from iodine by metal/hydrogen
HI returns: Hydroiodic acid is a highly selective reducing reagent for a wide variety of substrates. Its application is limited by the formation of iodine and the difficulty in reconverting that iodione back to HI in situ. We report the facile conversion of I2 to HI by metal-catalyzed hydrogenation in the presence of water, and demonstrate the utility of this process in the conversion of fructose to 5-methyfurfural and glycerol to 2-iodopropane. Copyright
Yang, Weiran,Grochowski, Matthew R.,Sen, Ayusman
scheme or table
p. 1218 - 1222
(2012/09/08)

Influence of mesoporous materials containing ZSM-5 on alkylation and cracking reactions
In order to increase the yield of cymene in alkylation of toluene with isopropanol, ZSM-5 zeolite units were incorporated into a mesostructured material. The catalysts were characterized by X-ray diffraction, TGA, SEM, NH3 temperature-programmed desorption and FTIR of pyridine adsorption. XRD analysis indicated that a structurally well ordered cubic MCM-48 aluminosilicate was successfully assembled from ZSM-5 zeolite seeds. The ZSM-5/MCM-48 catalyst exhibited significantly improved toluene conversion and yield of cymene product for toluene isopropylation. Catalytic tests show that the ZSM-5/MCM-48 composite material exhibits high catalytic activity compared with the conventional Y-zeolite for catalytic cracking of 1,3,5- triisopropylbenzene (TIPB). The exceptional catalytic performance of ZSM-5/MCM-48 catalyst in cracking and alkylation reaction was attributed to the easier access of active sites provided by the mesopores for both reactant and larger product molecules. The apparent activation energies for the cracking of 1,3,5-TIPB over ZSM-5/MCM-48 catalyst were found to decrease as follows: E C/CM-3 (tertiary cracking) > E C/CM-4 (disproportionation) > E C/CM-2 (secondary cracking) > E C/CM-1 (primary cracking).
Odedairo,Balasamy,Al-Khattaf
experimental part
p. 21 - 36
(2011/10/05)

FUEL COMPOSITIONS COMPRISING ISOPRENE DERIVATIVES
The invention provides for methods, compositions and systems using isoprene from a bioisoprene composition derived from renewable carbon for production of a variety of hydrocarbon fuels, fuel additives, and additives for fine chemistry and other uses.
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Page/Page column 71

(2012/01/06)

Regioselective arene functionalization: Simple substitution of carboxylate by alkyl groups
Arenes with various alkyl side-chains were synthesized in high yields and excellent regioselectivities. Starting from toluic and naphthoic acids, the carboxylate group was conveniently substituted by alkyl halides by Birch reduction and subsequent decarbonylation. The method is characterized by inexpensive starting materials and reagents, and methylation of arenes was realized. Besides simple alkyl substituents, the scope of arene functionalization was extended by benzyl, fluoro, amino, and ester groups. We were able to control the alkylation of 1-naphthoic acid during Birch reduction by the addition of tert-butanol. This allowed the regioselective synthesis of mono and bis-substituted naphthalenes from the same starting material.
Krueger, Tobias,Vorndran, Katja,Linker, Torsten
experimental part
p. 12082 - 12091
(2010/05/17)

Intermolecular hydroarylation of unactivated olefins catalyzed by homogeneous platinum complexes
Designing catalysts: The five-coordinate platinum(IV) complex A and the platinum(II) trans complex B act as precatalysts for the hydroarylation of unactivated olefins. The catalytic cycle features an aryl-olefin insertion at PtII and a C-H bond activation of the arene solvent as key steps. The Pt II cis complex C has been observed in hydroarylation reactions of ethylene with benzene.
Luedtke, Avery T.,Goldberg, Karen I.
supporting information; experimental part
p. 7694 - 7696
(2009/04/11)

Continuous, ionic liquid-catalysed propylation of toluene in a liquid-liquid biphasic reaction mode using a loop reactor concept
Acidic ionic liquids of the type [cation] [bis(trifluoromethanesulfonyl) imide anion]/aluminium trichloride {[cation] [(CF3SO 2)2N]/AlCl3} have been applied to realise for the first time a continuous Friedel-Crafts alkylation reaction in liquid-liquid biphasic reaction mode using a loop reactor concept. Exemplified for the continuous propylation of toluene we have proved that the acidic catalyst layer is successfully immobilised over at least 18 h in the loop reactor. After 8 h time-on-stream, a steady state has been reached followed by at least 10 h time-on-stream without any loss of activity or change in selectivity. Our results reveal the high potential of this class of acidic ionic liquids in continuous arene functionalisation reactions.
Ladnak, Viktor,Hofmann, Norbert,Brausen, Nicole,Wasserscheid, Peter
p. 719 - 726
(2008/02/09)

Liquid-phase noncatalytic oxidation of monoterpenoids with nitrous oxide
A series of monoterpenoids differing in the number of double bonds and the pattern of their substitution were tested in the liquid-phase noncatalytic oxidation with nitrous oxide (N2O). The structure of olefins has a significant effect on the oxidation route. In the case of terpenoids containing 1,1-disubstituted double bond, nor-carbonyl compounds are formed with high selectivity.
Romanenko,Starokon',Panov,Tkacheva
p. 1239 - 1243
(2008/09/17)

Identification by GC-MS of cymene isomers and 3,7,7-trimethylcyclohepta-1, 3,5-triene in essential oils
Retention indices of cymene isomers published in popular GC-MS atlases were found to be erroneous by analyzing synthetic samples. The following retention indices (RI) were found using a nonpolar phase (diphenyl: dimethylpolysiloxane, 5:95) for four essential-oil components with indistinguishable mass spectra: 3,7,7-trimethylcyclohepta-1,3,5-triene (RI = 970), m-cymene (RI = 1022), p-cymene (RI = 1024), and o-cymene (RI = 1039). The relative distributions of these compounds were evaluated based on the analysis of about 1000 essential oils. Simple methods were given for preparing standard mixtures of isomeric compounds for identification by GC-MS.
Romanenko,Tkachev
p. 699 - 701
(2008/02/08)

Reactions of alkyl radicals with substituted toluenes and the effect of substituents on dissociation energies of benzyl C-H bonds
Reactions of isopropyl and of undecyl radicals with meta- and para-substituted toluenes are reported. The results demonstrate that the reactivities of toluenes are due to both benzyl-H abstraction and addition of the alkyl radicals to the aromatic ring. Relative reactivities yield curved Hammett plots, consistent with kinetic data reported by Dutsch and Fischer. Abstractions and ring additions occur with comparable rates, but opposite Hammett slopes. Addition is favored by electron-withdrawing and abstraction by electron-donating substituents. The effects of substituents on the dissociation energies of benzyl C-H bonds are shown to be the major factor influencing reaction rates for benzyl-H abstraction by alkyl radicals.
Arafat, Abdelfattah M.,Mathew, Samuel K.,Akintobi, Solademi O.,Zavitsas, Andreas A.
p. 2226 - 2242
(2007/10/03)

Catalytic ring-attachment isomerization and dealkylation of diethylbenzenes over halide clusters of group 5 and group 6 transition metals
A molybdenum halide cluster, (H3O)2[(Mo 6Cl8)Cl6]·6H2O, possessing an octahedral metal framework was used as a catalyst in a gas flow reactor under 1 atm of hydrogen. On reaction of p-diethylbenzene, dehydrogenation to ethylstyrene proceeded selectively at 300°C. At 400°C, mutual interconversion of o-, m-, and p-diethylbenzenes proceeded selectively. The ethyl group migrated by an intramolecular 1,2-shift mechanism without yielding disproportionation products. Niobium and tungsten chloride clusters with the same metal framework were also active catalysts for the isomerization of p-diethylbenzene. All the reactions resulted in appreciable yields of dealkylation products. The catalytic activity for isomerization can be ascribed to acid sites on the cluster surface, and the catalytic activity for dealkylation, to the metallic nature of the framework metal.
Kamiguchi, Satoshi,Kondo, Kunihiko,Kodomari, Mitsuo,Chihara, Teiji
p. 54 - 63
(2007/10/03)

Simple two-step ipso substitution of aromatic carboxylic acids by alkyl halides
Methyl-substituted arenes can be synthesized with high regioselectivity in only two steps through formal exchange of an aromatic carboxylic acid function with an alkyl substituent. The results obtained with toluic acid illustrate that good to very good yields can be obtained from inexpensive reagents (see scheme).
Vorndran, Katja,Linker, Torsten
p. 2489 - 2491
(2007/10/03)

Influence of coke on the aromatization of 3-carene in the vapour phase over zeolites
Conversions of 3-carene to cymenes over Na13X, NaY and NaZSM-5 are less than over NaH13X (29% proton exchange), NaHY (33% proton exchange) and NaHZSM-5 (35% proton exchange). In the presence of oxygen, at its different partial pressures, the formation of cymenes increases significantly with increase in time on stream, indicating the formations of some species in the coke during the reaction which enhances the activity of the catalysts. To identify the species that cause enhancement of the activity, zeolite NaHY (catalyst B) has been doped with different amounts of NaOH and the reactions have been carried out over them at 350°C, at a contact time of 1.0 h (contact time is expressed as the reciprocal of Whsv, the weight hourly space velocity representing the weight of 3-carene passed over 1 g of catalyst per hour). The coke deposited has been examined by IR, ESR and XRD. Formation of quinone type of carbonyl group, responsible for the enhanced activity of the zeolites is observed. The participation of the quinone group in the dehydrogenation process is confirmed by extracting the coke after the reaction and the same reaction is carried out over the extracted coke both in the presence and in the absence of oxygen under the same experimental conditions. The quinone group is present in an atmosphere of oxygen but is absent if there is no oxygen.
Eswaramoorthy,Krishnasamy
p. 264 - 269
(2007/10/03)

Isomorphous substitution of chromium in AIPO-11 and AIPO-5 framework and their applications in the aromatization of 3-carene
CrAPO-11 and CrAPO-5 have been synthesized hydrothermally using aluminium isopropoxide, H3PO4, Cr(NO3)3 and di-n-propylamine for CrAPO-11 and triethylamine for CrAPO-5. The isomorphous substitution of Cr in AIPO-11 and AIPO-5 framework has been confirmed by XRD, SEM, DRS, MAS NMR, TGA, pore-volume and chemical analysis. Formation of cymenes (p-cymene and m-cymene) from 3-carene is higher over reduced than that over oxidized catalysts. The higher p/m (p-cymene/m-cymene) ratio, observed over reduced than over oxidized catalysts shows that p-cymene does not isomerise to m-cymene. The poisoning effects of pyridine and 4-methylquinoline are the same over large pore CrAPO-5 but different over medium pore CrAPO-11.
Eswaramoorthy,Mohan,Krishnasamy
p. 605 - 609
(2007/10/03)

Contributions of enthalpy and entropy factors to isomerization equilibrium of isopropyl- and cyclohexylbenzenes
Experimental and theoretical data on the liquid-phase equilibrium of the positional isomerization of isopropyl- and cyclohexylbenzenes are analyzed in detail. Contributions of the enthalpy and entropy factors to the equilibrium constants of the ortho-meta and para-meta transformations are estimated.
Nesterova,Pimerzin,Krasnykh
p. 1884 - 1890
(2007/10/03)

Indium trichloride catalyzed reductive Friedel-Crafts alkylation of aromatics using carbonyl compounds
Reductive Friedel-Crafts alkylation of aromatics with aldehydes or ketones using chlorodimethylsilane as a hydride source was effectively promoted by a catalytic amount of indium trichloride, whereas a popular type of Friedel-Crafts catalysts showed less effect.
Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
p. 6291 - 6294
(2007/10/03)

Influence of Protonation Exothermicity on Gas-Phase Concurrent Dealkylation and Isomerization of p-Cymene
The gas-phase protonation is reported of p-cymene (p-isopropyltoluene) by different radiolytically formed protonating agents (O2H+, N2H+, CH5+, COH+).The characteristics of the reactions vary with the protonation exothermicity.Both dealkylation and isomerization are observed with O2H+ or N2H+ ions.Only dealkylation occurs when the protonating agent is the CH5+ ion.Formation of products is not observed when the less energetic COH+ ions are employed.The results show that in the competition between isomerization and dealkylation the dealkylation reaction becomes favoured as the protonation exothermicity decreases.
Perez, Giorgio,Possagno, Elvira,Lilla, Edo
p. 623 - 626
(2007/10/02)

Nitration of Isopropylpyrenes. Strained Models for Protonation and Transfer-Nitration in the Condensed Phase
Protic mono- and dinitration of 1,3,5,7,9-pentaisopropylpyrene (1) occurred at the available α positions to give 2 and 3.Despite steric crowding, 2 and 3 did not exhibit a torsional barrier to i-Pr rotation at ambient temperatures; however, buttressing of the peri i-Pr groups was evident (1H NMR, UV, and force field energy minimizations).Persistent (dihydroxyiminium)pyrenium dications 2a+2 and 3a+2 were formed by low temperature protonation of 2 and 3 with CF3SO3H (TfOH)/SO2 or with FSO3H/SO2.Intramolecular cyclization of the nitro group of 2a+2 gave the rearranged pyrenium ion 2c+. 1 reacted with NO2+BF4- in acetonitrile solvent to give two pyrenium ions stable at rt, viz. the Wheland intermediate of α-nitration 2b+2 and the (dihydroxyiminium)pyrenium dication 2a+2; the latter was also the predominant pyrenium ion formed in the reaction of 1 with NO+BF4- in acetonitrile.Reaction of 1 with NO2+BF4- in chloroform solvent gave α-nitration products and a persistent radical cation RC.The simultaneous presence of α-nitration products and a persistent pyrenium RC was also observed in the reaction of 1 with NO+BF4- in chloroform, where broader NMR line widths and a stronger ESR signal suggested more extensive oxidation.Protic and aprotic nitrations of 1,3,6,8-tetraisopropylpyrene (10) occurred at the αβ positions; a minor addition product (26) was also found.A mixture of isomeric dinitropyrenes was obtained in NO2+ nitration of 1-isopropylpyrene (13).In line with low temperature protonation studies, aprotic nitrations of 2-isopropyl- and 4-isopropylpyrenes occurred predominantly at the α positions.The crowded pyrenium ion of 3 and 2 transfer nitrate to aromatics (toluene, mesitylene, benzene) under mild conditions in competition with a more facile transalkylation.
Laali, Kenneth Khosrow,Liang, Tze-Ming,Hansen, Poul Erik
p. 2658 - 2667
(2007/10/02)

Radiation-Induced Gas-Phase Concurrent Dealkylation and Isomerization of p-Cymene
D3+ ions, produced by deuterium γ-radiolysis, were allowed to react with gaseous p-cymene (p-isopropyltoluene).The reaction leads to the formation of excited arenium ions, which, if not stabilized by collision, undergo predominantly dealkylation and, alternatively, isomerization.Dealkylation is favoured with respect to isomerization by an increase in substrate concentration, these results showing that dealkylation requires a lower activation energy.
Perez, Giorgio,Lilla, Edo
p. 1119 - 1121
(2007/10/02)

A comparative study of gas phase aromatic desilylation and detertbutylation by charged electrophiles
Aromatic desilylation and detertbutylation by CH5+, C2H5+, i-C3H7+, and t-C4H9+ ions have been studied in the gas phase by mass spectrometric and radiolytic techniques.The higher rate of desilylation than of dealkylation in traced to the step involving the formation of ipso arenium ions, protonated at the ring carbon bearing the SiMe3 or the CMe3 substituent.The latter has been shown by ab initio calculations at the SCFSTO-3G level to selectively depress the basicity of the ipso position, hence the stability of the corresponding arenium ion relative to its protomers, e.g. the basicity of the ipso position of PhCMe3 is lower by ca. 11 kcal mol-1 than of the para position.The SiMe3 group has no comparable effect, very close basicities being computed for the para and the ipso position of PhSiMe3.The different effects of the CMe3 and SiMe3 groups are traced to electronic and steric factors.
Cacace, Fulvio,Crestoni, M. Elisa,Petris, Giulia De,Fornarini, Simonetta,Grandinetti, Felice
p. 3099 - 3107
(2007/10/02)

Competitive concerted and stepwise addition of free arylium ions to propane in the gas phase
Labelled tolylium ions from the decay of ring-multitritiated toluene have been allowed to react with propane in the gas phase, at pressures ranging from 20 to 744 Torr, yielding isomeric propyltoluenes as the major addition products. The relative composition of the n- versus iso-propyltoluenes (σp:σs 3.2-4.7) is found to depend appreciably upon the total pressure of the system and the presence of added bases (NH 3 or CH3OH). Pressure and base effects on the isomeric distribution of both n- and iso-propyltoluenes are also investigated. The results are consistent with a reaction pattern involving preliminary formation of an electrostatic adduct, wherein fast hydride-ion transfer from a secondary C-H bond of C3H8 to the arylium ion takes place. The same mechanism does not seem operative when the first interaction occurs between the tolylium ions and a primary C-H bond of the substrate. The behaviour of isomeric tolylium ions towards propane is discussed and compared with related studies involving unsubstituted phenylium ions. A mechanistic model is proposed for both reactions, which accounts for the apparent discrepancy between the indiscriminate affinity of arylium ions for any kind of substrate and their 'abnormally' high site selectivities.
Angelini, Giancarlo,Sparapani, Cinzia,Speranza, Maurizio
p. 1393 - 1400
(2007/10/02)

BORON, ALUMINUM, AND GALLIUM TRIS(TRIFLUOROMETHANESULFONATE) (TRIFLATE): EFFECTIVE NEW FRIEDEL-CRAFTS CATALYSTS.
Boron, aluminum, and gallium tris(trifluoromethanesulfonate) (triflate) were prepared from the corresponding chlorides (bromides) and triflic acid. The group IIIA triflates were isolated in pure form and fully characterized (elemental analysis, molecular weight, and NMR and IR spectroscopy). Boron tris(triflate) is a monomeric, relatively volatile compound left bracket mp 43-45 degree C, bp 68-73 degree C (0. 5 Torr) right bracket , whereas aluminum and gallium triflate are associated, high-melting associated solids. Boron, aluminum, and gallium tris(triflate) are efficient new Friedel-Crafts catalysts as shown in alkylation, isomerization, and acylation reactions. Alkylation of benzene and toluene with methyl, ethyl, isopropyl, and tert-butyl halides (fluoride, chloride, and bromide) were carried out with boron, aluminum, and gallium tris(triflate) as catalyst in CH//2Cl//2 and CH//3NO//2 solvent at room temperature.
Olah,Farooq,Morteza,Farnia,Olah
p. 2560 - 2565
(2007/10/02)

ORIENTATION IN METHYLATION AND PHENYLATION OF ALKYLBENZENES BY CATIONS GENERATED BY THE NUCLEAR CHEMICAL METHOD
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Sinotova, E. N.,Krylov, E. N.
p. 1042 - 1049
(2007/10/02)

Electrophilic Aromatic Substitution. 9. A Kinetic Study of the Friedel-Crafts Isopropylation Reaction in Nitromethane
The kinetics of the aluminum chloride catalyzed reaction between isopropyl chloride and benzene or toluene were determined in solvent nitromethane by using vacuum-line techniques.The reaction at 25 deg C was first order in isopropyl chloride and in aromatic hydrocarbon and first order in initial catalyst concentration.Noncompetitive results are kT/kB = 2.0 +/- 0.7 with the following toluene product isomer distribution: percent ortho, 45.3 +/- 1.5; percent meta, 22.7 +/- 1.1; percent para, 32.0 +/- 1.0.For competitive runs kT/kB was 2.3 +/- 0.1 with the same isomer distribution.Rate constants at 25, 15, 0, -15, and -27 deg C yielded Ea = 78 +/- 4 kJ/mol, ΔH = 76 +/- 4 kJ/mol, Δ = -13 +/- 14 J/mol deg.The results are consistent with a ? complex-like transition state and a predominantly ionic mechanism.
DeHaan, Franklin P.,Delker, Gerald L.,Covey, William D.,Ahn, Jeffrey,Cowan, Robert L.,et al.
p. 1587 - 1590
(2007/10/02)

Kinetics of Dehydration of Camphor and Fenchone over Alumina Catalysts
Kinetics of dehydration of camphor and fenchone to aromatics have been investigated over alumina of different acid strength in a flow reactor in the temperature range 300-405 deg.The dehydration activity increases with decreasing acid strength and fenchone is more reactive than camphor over all the three catalysts under the experimental conditions.The reactions follow first order kinetics.Energy of activation and other thermodynamic parameters are calculated.A linear regression analysis has been carried out to obtain isokinetic relationship which holds good for dehydration of camphor and fenchone with correlation coefficient of 0.98 and 0.96, respectively.
Krishnasamy, V.,Balasubramanian, K.
p. 213 - 215
(2007/10/02)

DISPROPORTIONATION OF HYDROGEN IN 3-CARENE
The disproportionation of hydrogen in 3-carene takes place with the formation of compounds of the 1,1,4-trimethylcycloheptane series.The proposed reaction mechanism involves dehydration of the 2-carene to 2,4-caradiene, which exists in a rapid tautomeric equilibrium with 3,7,7-trimethyl-1,3,5-cycloheptatriene.This gives rise to the appearance of compounds with a seven-membered ring in the reaction product.
Manukov, E. N.,Chuiko, V. A.,Vyglazov, O. G.
p. 257 - 262
(2007/10/02)

Cymenes as Xylene-substitutes by Catalytic Conversion of Indian Turpentine Over Supported Chromia and Platinum
Dehydrogenation of the constituents of Indian turpentine, viz., 3-carene, α-pinene and β-pinene to p- and m-cymenes has been investigated over chromia-alumina, chromia-alumina-potassium oxide and platinum-alumina catalysts in the vapour phase.Weak acidic alumina impregnated with low percentage of chromium is very effective in the conversion of 3-carene to p- and m-cymenes.Platinum-alumina, inlike chromium-alumina, develpos its catalytic activity in the lower temperature regions.The proportion of cymenes is always more from 3-cyrene than from pinenes.The total cymene content varies with the operation variables.The ratio of p-cymene to m-cymene (p/m) from 3-carene remains almost constant in the range of 1.5-2.0.Isokinetic relationship for the dehydrogenation of 3-carene over chromia-alumina-potassium oxide has been arrived at with a correlation coefficient of 0.988 and a standard deviation of 1.49.
Krishnasamy, V.,Balasubramanian, K.
p. 332 - 334
(2007/10/02)

Preparation, Pyrolysis, and Photolysis of Three Sterically Crowded Alkenes, 3,3,3',3',5,5,5',5'-Octamethyl-3,3',5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) 2,2,4,4-Tetramethyl-3-(3,3,5,5-tetramethyl-3,5-dihydro-4H-pyrazol-4-ylidene)-thietane 1,1-Dioxide and 2,2,2',2',4,4,4',4'-Octameth...
Photolysis and pyrolysis of the title compounds involve a stepwise elimination of nitrogen and/or sulphur dioxide and reactions which can be interpreted in terms of a series of trimethylenemethane (TMM) biradical intermediates.However, the photosensitised photolysis of the bi(pyrazolylidene) (11) give products indicative of an elimination of both nitrogens and the generation of a tetramethylene-ethane (TME) biradical intermediate.New synthesis of a number of highly sterically crowded alkenes including 2,2,4,4-tetramethyl-3-(3,3,5,5-tetramethyl-3,4-dihydro-4H-pyrazol-4-ylidene)thietane 1,1-dioxide (12) and 2,2,2',2',4,4,4',4'-octamethyl-3,3'-bithietanylidene 1,1,1',1'-tetraoxide (13), are described.Flash vacuum pyrolysis (f.v.p) of 3,3,3',3',5,5,5',5'-octamethyl-3,3'-5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) (11) at 400 deg C gives 3,3,5,5-tetramethyl-4-(2,2,3,3-tetramethylcyclopropylidene)-3,5-dihydro-4H-pyrazole (21), at ca. 400 deg C 1-isopropylidene-2,2,4,4,5,5-hexamethylspiropentane (22), and at ca. 580 deg C a ca. 5:1 mixture of 4-isopropyl-3-isopropylidene-2,5-dimethylhexa-1,4-diene (23) and 2-(2,3-dimethylbut-1-en-3-yl)-1-isopropyl-3,3-dimethylcyclopropene (27).Above 700 deg C a complex mixture of aromatic products and low molecular weight hydrocarbons is produced which includes ethane, ethylene, propene, isobutane, and isobutene, p-xylene, o-cumene and probably m-cumene, and 2,5-dimethylisopropylbenzene.F.v.p. of the dihydropyrazole sulphone (12) gives initially 2,2,4,4-tetramethyl-3-(2,2,3,3,-tetramethylcyclopropylidene)thietane 1,1-dioxide (41) and at higher temperatures similar mixtures to those obtained from the bipyrazolylidene (11).Similar results were also obtained for the f.v.p. of the bis-sulphone (13).Photolysis of the bipyrazolylidene (11) gave initially the dihydropyrazole (21) and then a 48:52 mixture of the spiro compound (22) and 2,2,2',2',3,3,3',3'-octamethylbicyclopropylidene (42).Photolysis of the dihydropyrazole sulphone (12) gave 2,2,4,4-tetramethyl-3-(2,2,3,3-tetramethylcyclopropylidene)thietane 1,1-dioxide (41).Benzophenone-sensitised photolysis of the bipyrazolylidene (11) gave 1,2-di-isopropylidene-3,3,4,4-tetramethylcyclobutane (32).
Bushby, Richard J.,Mann, Stephen,Jesudason, Malini, V.
p. 2457 - 2464
(2007/10/02)

FRIEDEL-CRAFTS ALKYLATION OF ANISOLE AND ITS COMPARISON WITH TOLUENE. PREDOMINANT ORTHO-PARA SUBSTITUTION UNDER KINETIC CONDITIONS AND THE EFFECT OF THERMODYNAMIC ISOMERIZATIONS
The AlCl3 and BF3, as well as 65percent HPF6, catalyzed Friedel-Crafts alkylation of anisole with alkyl halides and alkohols was investigated.The alkylation of anisole with lower catalyst concentrations under mild conditions shows predominant ortho/para directing effect generally with a ratio of c.a. 2:1, with the amount of meta isomer uniformly less than 3percent.With "swamping" catalyst conditions the amount of meta substitution in methylation and ethylation can substantially increase.The isomer distribution in tert-butylation changes with time due to rapid ortho-para interconversion.Consequently, the AlCl3-catalyzed isomerization of isomeric alkylanisoles was also studied.In case of tert-butylanisoles, the ortho isomer shows relatively rapid conversion into para followed by much slower isomerization to meta.The para and meta isomers show isomerization to meta-para mixtures.Isomerization of ethyl-, isopropyl-, and benzylanisoles is generally slow whereas methylanisoles do not isomerize.Comparing results of the alkylation of anisole with toluene leads to the conclusion that the latter are readily affected by concurrent (and in some cases consecutive) isomerization.As the barrier for isomerization in the benzenium ion intermediates of the alkylations is higher in the case of CH3O- than CH3-substituted systems, anisole tends to give the kinetically controlled ortho-para alkylation products and the amount of meta isomer is low.Study of alkylation of 3,5-di- and 2,4,6-trideuterated toluene and anisole and comparing retained deuterium contents with isomer distributions shows that alkylated product formation in case of toluene, but not of anisole, is proceeded by intramolecular, 1,2-alkyl, and hydrogen-deuterium shifting resulting also in increased meta substitution.This effect is most predominant in methylation and ethylation where the alkyl shifts are intramolecular but not in tert-butylation and benzylation, where alkyl transfer is intermolecular.Isopropylation is intermediate in nature.No simple selectivity-reactivity relationship is indicated in the studied alkylation reactions.As shown in benzylations with increasingly electron-donating and -withdrawing substituted benzyl chlorides overall rate (i.e., substrate selectivity) and isomer distributions (i.e., regioselectivity) are not determined in the same step as significantly decreased substrate selectivity is not accompanied by loss of positional selectivity.Previously reported alkylations showing high degree of meta substitution therefore, must have been affected by thermodynamically controlled rearrangement processes, including intramolecular alkyl and hydrogen shifts in the arenium ion intermediates of the alkylation reactions.These are to be differentiated from possible subsequent product isomerizations.Under predominantly kinetic conditions anisole as well as toluene are substantially ortho-para directing in alkylations, as in other electrophilic aromatic substitutions.
Olah, George A.,Olah, Judith A.,Ohyama, Toshiyuki
p. 5284 - 5290
(2007/10/02)

THE "SUPER-BASIC" BUTYLLITHIUM/POTASSIUM TERT-BUTOXIDE MIXTURE AND OTHER LICKOR-REAGENTS
The reactivity pattern of the butyllithium/potassium tert-butoxide mixture differs significantly from that of butylpotassium and thus disproves the claimed identity of these two reagents.
Schlosser, Manfred,Strunk, Sven
p. 741 - 744
(2007/10/02)

Utilization of Indian Turpentine. Catalitic Transformation Studies of α-Pinene, Δ3-Carene, Camphene and Tricyclene to Cymenes: Kinetic Aspects
The isomerization and aromatization of α-pinene, 3-carene, camphene and tricyclene to cymenes have been investigated over alumina and chromia-alumina of varying acid strength and also over chromia in the temperature range 235 to 500 deg C.These transformations follow second order kinetics.The isomerization of these compounds depends on the amount and strength of acid sites. Impregnation of these catalysts with small amounts of potassium ions decreases their isomerization activity and increases their dehydrogenation ability.Hydrofluoric acid does the reverse.Pyridine suppresses both overall conversion and the formation of cymenes.The ratio p/m* from 3-carene is higher over chromia than over chromia-alumina, it increases with the addition of potassium ions and decreases with that of fluorine ions.The p/m begins to fall when the reaction temperature rises above 450 deg C.
Krishnasamy, V.,Mohan, V.
p. 359 - 363
(2007/10/02)

HYDROGENATION AND DISPROPORTIONATION OF HYDROGEN IN 3-CARENE
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Manukov, E. N.,Chuiko, V. A.,Vyglazov, O. G.
p. 242
(2007/10/02)

GAS PHASE ISOPROPYLATION OF AROMATIC HYDROCARBONS. FLUORINE AND METHYL SUBSTITUENT EFFECTS ON REACTIVITY AND ORIENTATION.
The isopropylation of substituted benzenes by s-C3H7+ cations is studied to evaluate the directive effects of fluorine, methyl group and their combinations as ring substituents in the gas-phase aromatic substitution.
Attina, Marina,Petris, Giulia de,Giacomello, Pierluigi
p. 3525 - 3528
(2007/10/02)

Dehydrogenation of 3-Carene in the Vapour Phase. II. Performance Studies of Chromia and Chromia-Alumina Catalysts
The influence of contact time on the dehydrogenation of 3-carene over reduced chromia and chromia-alumina catalysts has been investigated at 450 and 400 deg C resepectively.For the dehydrogenation, reduced chromia-alumina catalyst is more active than reduced chromia alone.It has been found that the dehydrogenating ability of reduced chromia is superior to that of oxidized chromia.The effect of water vapour on reduced chromia showed an initial suppression of its reactivity, but at intermediate values increased its activity.Progressive increase of water vapour wasseen to modify the active sites of reduced chromia, an effect similar to that of the oxidized sample.The dehydrogenation of 3-carene, over chromia, follows second-order kinetics.The energy of activation is found to be greater for oxidized than for reduced chromia.Impregnation of chromia with potassium decreases the activation energy of reduced chromia and enhances its dehydrogenation ability by suppressing the side reactions.The observed experimental data are explained in terms of the acidity of the catalysts, oxidation states of chromium ions and the promoting influence of potassium ions.
Krishnasamy, V.
p. 1313 - 1321
(2007/10/02)

TRANSPOSITIONS THERMIQUES DE DERIVES HALOGENES DU DIMETHYLENECYCLOBUTANE ET DU METHYLENECYCLOBUTENE.
The title substances are converted by pyrolysis, in fair to excellent yields, into aromatic hydrocarbons.
Maurin, Robert,Piscot, Christian,Charrouf-Chafchaouni, Zoubida
p. 2425 - 2428
(2007/10/02)

Aromatic Substitution in the Gas Phase. A Comparative Study of the Alkylation of Benzene and Toluene with C3H7+ Ions from the Protonation of Cyclopropane and Propene
Gas-phase alkylaton of benzene and toluene has been used as a probe to sample the isomeric population of C3H7+ ions obtained from the protonation of cyclopropane and of propene, respectively, with H3+ ions in H2 gas at pressures from 50 to 720 torr.The reagent from cyclopropane promotes extensive (over 40percent) n-propylation, in addition to isopropylation of the arenes, on contrast to the reagent from propene that yields only traces of n-propylated products.The n-propylating reagent is identified as protonated cyclopropane, whose lifetime must exceed 10-7 s in the gaseous systems investigated.The mechanism and the selectivity of the gas-phase alkylation are discussed and compared to relevant mass spectrometric and kinetic results.
Attina, Marina,Cacace, Fulvio,Giacomello, Pierluigi
p. 4768 - 4772
(2007/10/02)

Catalytic Property of Calcined Iron Sulfate Treated with Hydrogen Chloride in Alkylation of Toluene and Benzene with Alkyl Chlorides
Alkylation was carried out at room temperature over catalysts prepared by calcination of FeSO4, Fe2O3, and Fe(OH)3 in the air at various temperatures and subsequent exposure to HCl at room temperature for 20 min.The FeSO4-HCl catalysts heat-treated at 700 and 750 deg C showed very high activity and selectivity, the other catalysts except for the sulfate treated at 800 deg C being almost inactive.The FeSO4(700 deg C)-HCl catalyst was found to consist of FeCl3 and α-Fe2O3 by means of Moessbauer effect, the absorption peak areas being 14 and 86percent for portions of iron based on the chloride and oxide, respectively.The results of DTA and TGA experiments suggest that the coordinate bond of water molecule on FeCl3 of the FeSO4(700 deg C)-HCl catalyst is stronger than that on FeCl3 of the FeSO4 (600, 800, and 900 deg C)-HCl and commercial FeCl3.The FeSO4(700 deg C)-HCl catalyst showed a much higher activity than pure FeCl3.The iron(III) chloride formed by reaction of HCl and α-Fe2O3 obtained by thermal decomposition of the sulfate at 700 or 750 deg C was found to be a very strong Lewis acid catalyst.
Arata, Kazushi,Hino, Makoto,Yabe, Katsumasa
p. 6 - 9
(2007/10/02)