- Carbocationic polymerization of isoprene using cumyl initiators: Progress in understanding side reactions
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The cationic polymerization of isoprene using cumyl chloride/B(C6F5)3 and cumyl ether/TiCl4 systems was investigated in dichloromethane or in dichloromethane/methylcyclohexane mixtures varying the polymerization conditions. Polymerizations were performed in all cases in the presence of a large excess of a proton trap (2,6-di-tert-butyl pyridine, dtBP) compared to initiator in order to suppress any protic side reactions. As a consequence, no polymerization went to completion. Independently of the reaction conditions, trans-1,4-oligomers were exclusively obtained with mainly an olefinic terminal group. It was highlighted that an important loss of double bonds yielding saturated parts was observed, even in the absence of protons, assuming that a great amount of double bond loss generally observed in isoprene cationic polymerization could be due to intramolecular cyclization reactions. Nevertheless, under particular conditions (low temperature and/or low polarity medium), branching and cross-linking reactions were also found responsible for double bond loss.
- Ouardad, Samira,Wirotius, Anne-Laure,Kostjuk, Sergei,Ganachaud, Fran?ois,Peruch, Frédéric
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Read Online
- First X-ray crystallographic study of a benzyl cation, cumyl hexafluoroantimonate(V), and structural implications
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The crystal structure of the cumyl cation (1; 2-phenyl-2-propyl cation) has been determined at -124°C (as hexafluoroantimonate, 1.SbF6; R1 = 0.0502, wR2 = 0.1054). The cation 1 is nearly planar and has a short C+-C(ipso) bond (1.41(2) A?) and bond lengths in the phenyl ring which agree with strong benzylic delocalization. The weak but distinct shortening of the C+-CH3 bonds by 0.025(12) A? indicates weak C-H hyperconjugation. Nearly all H atoms are involved in H...F contacts to SbF6 anions, and one close C+...F contact (3.11 (2) A?) is observed. The phenyl rings form infinite stacks and are shifted against each other in the stack.
- Laube, Thomas,Olah, George A.,Bau, Robert
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Read Online
- Thiourea-Mediated Halogenation of Alcohols
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The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
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supporting information
p. 12901 - 12911
(2020/11/26)
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- Desulfurative Chlorination of Alkyl Phenyl Sulfides
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The chlorination of readily available secondary and tertiary alkyl phenyl sulfides using (dichloroiodo)benzene (PhICl2) is reported. This mild and rapid nucleophilic chlorination is extended to sulfa-Michael derived sulfides, affording elimination-sensitive β-chloro carbonyl and nitro compounds in good yields. The chlorination of enantioenriched benzylic sulfides to the corresponding inverted chlorides proceeds with high stereospecificity, thus providing a formal entry into enantioenriched chloro-Michael adducts. A mechanism implying the formation of a dichloro-λ4-sulfurane intermediate is proposed.
- Canestrari, Daniele,Lancianesi, Stefano,Badiola, Eider,Strinna, Chiara,Ibrahim, Hasim,Adamo, Mauro F. A.
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p. 918 - 921
(2017/02/26)
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- Mechanistic insight into the thermal 1,3-chlorine migrations of N-chloroacetanilides under neutral conditions
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The mechanistic insight of the thermal 1,3-chlorine migration reactions of N-chloroacetanilides under neutral conditions has been investigated. The results indicate that the 1,3-chorinemigration reaction is initiated by the radical reaction of the homocleavage of the Cl-N bond and subsequent radical combination of the Cl-C bond on the aromatic rings. The radical mechanism was verified by the thermal rearrangement of Nchloro- N-(4-methylphenyl)acetamide in cumene. After generation of hydrochloric acid in the radical mechanism, the migrations occurred through the acid-catalyzed rearrangement as well as the acid-catalyzed Orton reaction. The current results provide a comprehensive understanding on the mechanistic insights in the Orton reaction under different conditions.
- Cheng, Baoxiang,Xu, Jiaxi
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p. 518 - 525
(2017/05/01)
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- Direct halogenation of alcohols with halosilanes under catalyst- and organic solvent-free reaction conditions
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A chemoselective method for the direct halogenation of different types of alcohols with halosilanes under catalyst- and solvent-free reaction conditions (SFRC) is reported. Various primary, secondary and tertiary benzyl alcohols and tertiary alkyl alcohols were directly transformed to the corresponding benzyl and alkyl halides, respectively, using chlorotrimethylsilane (TMSCl) and bromotrimethylsilane (TMSBr).
- Ajvazi, Njomza,Stavber, Stojan
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supporting information
p. 2430 - 2433
(2016/05/19)
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- A Visible-Light-Induced α-H Chlorination of Alkylarenes with Inorganic Chloride under NanoAg@AgCl
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An efficient, photocatalytic chlorination of alkylarene α-H groups using NaCl/HCl as a chlorine source has been developed, which involves a radical mechanism under visible-light (including sunlight) conditions. A chlorine radical is proposed to be formed by an electron transfer from chloride ion to O2 in air through the bandgap hole of the semiconductor AgCl. The chlorination protocol is characterized by its use of natural sunlight or other visible light, mild conditions, cheap source of chlorine, green solvent, and high selectivity. The yield of benzylchloride is 95 % with a toluene conversion as high as 40 %, which rivals traditional chlorination methods.
- Liu, Shouxin,Zhang, Qi,Li, Huiying,Yang, Yihua,Tian, Xia,Whiting, Andrew
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supporting information
p. 9671 - 9675
(2015/06/30)
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- Iron-catalyzed borylation of alkyl electrophiles
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The use of low-cost iron(III) acetoacetate (Fe(acac)3) and tetramethylethylenediamine (TMEDA) enables the direct cross-coupling of alkyl halides with bis(pinacolato)diboron. This approach allows for the borylation of activated or unactivated primary, secondary, and tertiary bromides. Moreover, even the borylation of benzylic or allylic chlorides, tosylates, and mesylates are possible. The reactions proceed under mild conditions at room temperature and show broad functional-group compatibility and "robustness" as measured by a modified Glorius robustness screen.
- Atack, Thomas C.,Lecker, Rachel M.,Cook, Silas P.
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supporting information
p. 9521 - 9523
(2014/07/22)
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- Solvolysis of 2-chloro-2(3,4-disubstituted) phenylpropanes: Validity of Hammett-Brown σ+ constants in assessing additive effects of substituents
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The objective of this study is to test the suitability of the extended Hammett-Brown equation, log (kXX/kHH) = ρ+∑σ+, in depicting satisfactorily additive effects of electronegative atom-bearing substituents, which are known to possess diverse and multicomponent influences on the side chain reactions of polysubstituted benzenes. The equation has been used to correlate, for the first time, the additive effect of substituents in the specific rates of solvolysis of 2-chloro-2-phenylpropanes (3b-3f) having 3-F,4-Me, 3-Br,4-Me, 3-I,4-Me, 3-Me,4-Me, or 3-MeO,4-Me substituents. The rates were determined titrimetrically at 288, 298, and 308 K using 90% aqueous acetone as solvent. Measured additive effects of these substituents on the solvolysis rate and activation parameters of the parent cumyl chloride (2-chloro-2-phenylpropane) are found to be well correlated using the equation given above. Plots of log (kXX/k HH) of 3b-3f together with mainly di-, but also tri- and mono-substituted cumyl chlorides from previous studies against ∑σ+ give a linear correlation coefficient of 0.990 as a measure of the validity of the equation to depict such systems. The halogen substituents' extent of conformity with additivity reflected in their relative (kobsd/kcalcd) rate ratios is found to correlate with the steric size of substituents. Plots of rate ratios against Taft's steric factor of each halogen give a linear correlation coefficient of 0.994 for the 3-halo substituents. The 3,4-dimethyl substituents' relative rate ratio of 1.03 shows excellent additivity, whereas the 3-methoxy-4-methyl ratio of 1.43 shows the methoxy group to be far less deactivating than predicted. Similar trends were found for the free energy of activation (δG? - δG 0?) differences, which correlated linearly with a coefficient of 0.983 with Taft's steric factor of halogen atoms.
- Taha, Ahmed A.
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scheme or table
p. 514 - 523
(2012/07/28)
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- Hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine
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Non-heme iron halogenases, such as SyrB2 and CytC3, catalyze the regioselective chlorination and bromination of aliphatic C-H bonds. Reported here is the hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The reactions between these coordination compounds and meta-chloroperbenzoic acid generate oxidants capable of oxidizing weak C-H bonds to C-Cl bonds. This chemistry is regioselective, with a strong preference for activating C-H bonds on secondary carbons over weaker C-H bonds on tertiary carbons. The reactivity is consistent with the methyl groups on the ligands preventing more sterically encumbered substrates from accessing the reactive portions of a [MIV(LMen)(O)Cl2] oxidant. The iron compounds promote more hydrocarbon chlorination than their manganese analogs.
- Goldsmith, Christian R.,Coates, Cristina M.,Hagan, Kenton,Mitchell, Casey A.
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scheme or table
p. 24 - 30
(2011/04/22)
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- Room temperature living cationic polymerization of styrene with HX-styrenic monomer adduct/FeCl3 systems in the presence of tetrabutylammonium halide and tetraalkylphosphonium bromide salts
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Living cationic polymerization of styrene was achieved with a series of initiating systems consisting of a HX-styrenic monomer adduct (X?=?Br, Cl) and ferric chloride (FeCl3) in conjunction with added salts such as tetrabutylammonium halides (nBu4N+Y-; Y-?=?Br-, Cl-, I-) or tetraalkylphosphonium bromides [nR′4PBr; R′?=?CH3CH2-, CH3(CH2)2CH2-, CH3(CH2)6CH2-] or tetraphenylphosphonium bromide [(C6H5)4PBr] in dichloromethane (CH2Cl2) and in toluene. Comparison of the molecular weight distributions (MWDs) of the polystyrenes prepared at different temperatures (e.g., -25?°C, 0?°C and 25?°C) showed that the polymerization is better controlled at ambient temperature (25?°C). The polymerization was almost instantaneous (completed within 1?min) and quantitative (yield ~100%) in CH2Cl2. In CH2Cl2, polystyrenes with moderately narrow (Mw/Mn?~?1.33-1.40) and broad (Mw/Mn?~?1.5-2.4) MWDs were obtained respectively with and without nBu4N+Y-. However, in toluene, the MWDs of the polystyrenes obtained respectively with and without nBu4N+Y-/nR′4P+Br- were moderately narrow (Mw/Mn?=?1.33-1.5) and extremely narrow (Mw/Mn?=?1.05-1.17). Livingness of this polymerization in CH2Cl2 was confirmed via monomer-addition experiment as well as from the study of molecular weights of obtained polystyrenes prepared simply by varying monomer to initiator ratio. A possible mechanistic pathway for this polymerization was suggested based on the results of the 1H NMR spectroscopic analysis of the model reactions as well as the end group analysis of the obtained polymer.
- Banerjee, Sanjib,Paira, Tapas K.,Kotal, Atanu,Mandal, Tarun K.
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experimental part
p. 1258 - 1269
(2011/04/18)
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- PROCESS FOR PRODUCTION OF CHLORINATED AROMATIC COMPOUND
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[PROBLEMS] To provide a simpler method for producing a high-quality chlorinated aromatic hydrocarbon (e.g., cumylchloride), which can be used as a cationic polymerization initiator. [MEANS FOR SOLVING PROBLEMS] A chlorinated aromatic hydrocarbon can be produced by repeating both (a) the step of performing chlorination reaction by stirring an organic solution containing a compound represented by Ar(R1C=CH2)n with an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 30% by weight or higher and (b) the step of removing the water phase in part or whole from the reaction solution produced in the step (a), and then adding an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 30% by weight or higher to the reaction solution, until the chlorination reaction rate of the compound reaches a predetermined level.
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Page/Page column 6-7
(2010/11/30)
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- An efficient method for chlorination of alcohols using PPh3/Cl3CCONH2
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A new and convenient method for the chlorination of alcohols utilizing PPh3/Cl3CCONH2 is addressed. Various alcohols could smoothly be converted into their corresponding alkyl chlorides in high yield under mild conditions with short reaction times. A mechanism is disclosed with the evidence of inversion of configuration of the analogous alkyl chloride derived from R-(-)-2-octanol.
- Pluempanupat, Wanchai,Chavasiri, Warinthorn
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p. 6821 - 6823
(2007/10/03)
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- Kinetics of elimination reactions of cumyl chloride and its substituted derivatives in acetonitrile
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A cent per cent unimolecular elimination reaction of tertiary aralkyl halides in acetonitrile is being reported for the first time. The reversibility in the rate determining step can be prevented by the addition of a weak base like pyridine in cumyl chloride and its α- and p-substituted derivatives. A plot of logarithmic rate constants of α-substituted cumyl chloride against Charton's steric parameter 'v' gives a linear relationship.
- Balachandran,Santhosh Kumar
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p. 1731 - 1734
(2007/10/03)
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- Indium-catalyzed direct chlorination of alcohols using chlorodimethylsilane-benzil as a selective and mild system
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The InCl3-catalyzed reaction of alcohols with chlorodimethylsilane (HSiMe2Cl) in the presence of benzil gave the corresponding organic chlorides under mild conditions. Benzil significantly changes the reaction course because the reducing product through dehydroxyhydration was obtained in the absence of benzil. The secondary or tertiary alcohols were effectively chlorinated. The substrates bearing acid-sensitive functional groups were also applied to this system. The highly selective chlorination of the tertiary site was observed in the competitive reaction between tertiary and primary alcohols. The highly coordinated hydrosilane generated from benzil and HSiMe2Cl is an important intermediate. Copyright
- Yasuda, Makoto,Yamasaki, Satoshi,Onishi, Yoshiyuki,Baba, Akio
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p. 7186 - 7187
(2007/10/03)
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- Process for preparing dithioesters
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The present invention relates to a process for preparing dithioesters in which a dithiocarboxylic acid and/or a dithiocarboxylic salt is reacted with a vinyl compound and/or an alkyl compound which includes a leaving group, the reaction being carried out in a biphasic system in which one of the phases comprises water and the weight ratio of the aqueous phase to the organic phase lies in the range from 95:5 to 5:95.
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- Method for producing aromatic compounds having alkyl group with at least three carbon atoms
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Aromatic compounds having an alkyl group with at least 3 carbon atoms are produced in a process comprising at least one of the following steps: (1) a step of contacting a starting material that contains an aromatic compound having a branched alkyl group with at least 3 carbon atoms, with a zeolite-containing catalyst in a liquid phase in the presence of hydrogen therein, thereby changing the position of the carbon atoms of the alkyl group bonding to the aromatic ring of the compound; (2) a step of contacting a starting material that contains an aromatic compound having a branched alkyl group with at least 3 carbon atoms, with a catalyst containing zeolite and containing rhenium and/or silver, in a liquid phase, thereby changing the position of the carbon atoms of, the alkyl group bonding to the aromatic ring of the compound; (3) a step of contacting a halogenated aromatic compound having an alkyl group with at least 3 carbon atoms, with an acid-type catalyst, thereby isomerizing the compound; (4) a step of treating a mixture of isomers of an aromatic compound having an alkyl group with at least 3 carbon atoms, with a zeolite adsorbent that contains at least one exchangable cation selected from alkali metals, alkaline earth metals, lead, thallium and silver, thereby separating a specific isomer from the isomer mixture through adsorption.
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- Synthesis and end group structure of 2-deoxydextrans prepared via the cationic ring-opening polymerization of an anhydro sugar
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1,6-Anhydro-3,4-di-O-benzyl-2-deoxy-β-D-glucose was polymerized using 1-chloroethyl isobutyl ether or cumyl chloride as initiator and ZnI2 as activator. The resulting polymer contained predominantly α-(1,6) linkages, and the molecular weight distributions were narrow (≤ 1.25). The kinetics of polymerization was first-order with respect to monomer concentration. There was evidence of slow chain transfer at these polymerization temperatures, although the majority of polymer chains contained the initiator fragment. Mass spectra of the polymer revealed that the initiator fragment at the polymer chain end was an isobutyl group, presumably arising from nucleophilic attack of monomer on the methylene unit of the isobutyl group in the initiating cation with loss of acetaldehyde as opposed to attack at the Sp2-methylene carbon. Cyclic oligomers were present in the polymer sample as well and could have arisen from two processes: HCl initiation or a backbiting reaction.
- Liang, Yu-Zeng,Franz, Andreas H.,Newbury, Chrisana,Lebrilla, Carlito B.,Patten, Timothy E.
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p. 3402 - 3412
(2007/10/03)
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- Reactivity of bismuth(III) halides towards alcohols. A tentative to mechanistic investigation
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The reactivity of bismuth(III) halides (BiX3; X=Cl, Br and I) towards a series of alcohols has been investigated. Three different reactions have been studied, namely: halogenation, dehydration and etherification. The behaviour of these bismuth derivatives was found to depend on the nature of the halide bonded to the bismuth atom. Their reactivities can be interpreted on the basis of the Hard and Soft Acids and Bases (HSAB) principle. A mechanism is proposed which involves the formation of a complex of the alcohol with Bi(III).
- Keramane, El Mehdi,Boyer, Bernard,Roque, Jean-Pierre
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p. 1909 - 1916
(2007/10/03)
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- Electronic properties of the nitrone substituent. Stabilization of benzylic carbocations
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The nitrone substituent CH=N(O) t-Bu is electron-withdrawing with a Taft σI value of 0.20. It also retards the solvolysis rate of a cumyl chloride when placed in the meta-position (σ = 0.20). However, CH=N(O) t-Bu becomes weakly cation stabilizing when placed in the para-position of a cumyl cation (σ+ = -0.04). This weak cation stabilization is a result of a conjugative interaction which delocalizes charge and offsets the inductive effect of the nitrone. When the nitrone is placed in the para-position, but then twisted out of conjugation with the aromatic ring by incorporation of flanking 3,5-dimethyl groups, it again retards solvolysis rates. Computational studies (B3LYP/6-31G*) show that the nitrone substituent stabilizes a para-substituted benzyl cation relative to the meta-substituted analog by a conjugative interaction. However, the calculated stabilization greatly overestimates the cation stabilization seen in solvolytic reactions. Copyright
- Creary, Xavier,Hartandi, Kresna
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- Interpretation of retention indices in gas chromatography for establishing structures of isomeric products of alkylarenes radical chlorination
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By an example of previously uncharacterized products obtained by alkylarenes radical chlorination was demonstrated that combination of various interpretation methods applied to the retention indices (RI) in the gas chromatography on the standard nonpolar phases (comparison of RI of products and initial compounds, characteristics of succession of the chromatographic elution of the structural isomers with the use of estimation of molecular dynamic parameters, application of the additive schemes to RI calculation, and using of structural analogy CH3?Cl for testing the results obtained) permitted unambiguous identification of the structure even without data of mass spectrometry.
- Zenkevich
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p. 270 - 280
(2007/10/03)
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- Simple synthetic protocols for tertiary alkyl and allyl thiols
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Convenient preparative methods for tertiary alkyl and allyl thiols are described. Accordingly, thiolesters and thiocyanates, obtained from the reaction of SN1-active halides and appropriate zinc salts, on hydrolysis and LAH reduction respectively, afford the corresponding thiols in near quantitative yields. Besides the well known p-menth-1-ene-8-thiol, p-menthane-1-thiol, p-mentha-1,8-diene-6-thiol and 2-(2-phenyl)propane thiol have been prepared.
- Gurudutt, K. N.,Rao, Sanjay,Srinivas, P.,Srinivas, S.
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p. 1169 - 1171
(2007/10/03)
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- Substituent Effects on the CC Bond Strength, 16. - Thermal Stability and Enthalpies of Formation of β-Dicarbonyl Compounds. - Stabilisation Enthalpies of α,α'-Diketoalkyl Radicals
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The geminal interactions of the two carbonyl groups in seven β-diketones of the type 8-9 and 11-13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization.The radical stabilisation enthalpies RSE of the α,α'-diketoalkyl radicals 9-13 were obtained from the enthalpies of activation ΔH(excit.) of thermal CC bond cleavage of eight model compounds of the type 9-13 by their comparison with ΔH(excit.) of comparable hydrocarbons of similar strain.For non-cyclic α,α'-diacylalkyl radicals and six-membered cyclic ones RSE = 54.8 +/- 1.3 kJ mol-1 was determined, which indicates an additive stabilisation by two carbonyl groups. - Key Words: Enthalpies of formation/ Geminal substituents, energetic interaction of/ Bond cleavage, C-C, kinetics of/ Radicals, stability of/ Increments, thermochemical/ Bond strength, substituent effects on
- Noelke, Margot,Verevkin, Sergej P.,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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- RETROVIRAL PROTEASE INHIBITING COMPOUNDS
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A retroviral protease inhibiting compound of the formula: STR1 is disclosed wherein R 1, R 2, R 5, R 6, Y m and Y' n are herein defined.
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- The Reaction between Acyl Halides and Alcohols: Alkyl Halide vs. Ester Formation
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In the reaction between an acyl halide and an alcohol the thermodynamically favoured products are the free carboxylic acid and the alkyl halide.The initial reaction is, generally, the formation of an ester and HHal.When the alcohol is very prone to yield an alkyl cation upon protonation by HHal, formed H2O exhibited a superior reactivity and competed successfully with the alcohol for the acyl halide making, therefore, ester formation practically confined to a triggering role.But, in those cases where the cation is less easily formed, ester formation was favoured and, consequently, became the necessary elementary step towards alkyl halide formation.Tis final product, on the other hand, might be extremely slow to form in an SN2 reaction between the protonated ester function and the halide ion.In these instances, therefore, as well as in the cases when a basic solvent competes for the proton of HHal, the ester is the final product.A notable exception of the situation above outlined, is given by α-hydroxy-α-phenylbenzeneacetic acid (2y), which appears to undergo direct chlorine-hydroxyl interchange through a quaternary intermediate (E), in the end collapsing to α-chloro-α-phenyl-benzeneacetic acid (4y).Different systems were compared using CH2Cl2 as a solvent under strictly similar conditions.Some 28 different substrates were tested for reaction with AcCl (1a), whereas the action of eight acyl halides (a) against (RS)-α-methylbenzenemethanol (2n) and α-phenylbenzenemethanol (2p), as well as the effect of five different solvents on the reaction between two alcohols (2p and 2-methyl-2-propanol, 2c) with 1a, were observed.
- Strazzolini, Paolo,Giumanini, Angelo G.,Verardo, Giancarlo
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p. 217 - 254
(2007/10/02)
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- Aromatic transformation process
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A process is provided for transaralkylating a class of starting compounds comprised of aryl-substituted lower alkanes and aryl-substituted fused alkylene ring compounds to produce derivatives of such compounds wherein benzyl substituents thereof have different alkyl substituents compared to the starting compounds. The process is carried out by admixing such a starting compound with a lower alkyl-substituted aromatic compound under liquid phase conditions in the presence of a catalytically effective amount of a Friedel-Crafts catalyst. The process makes possible new and economical routes for synthesizing desired lower alkyl-substituted benzyl group containing compounds, such as 2,2-di(lower alkyl-substituted) phenyl propanes and 1,3,3-trimethyl-1-(lower alkyl-substituted)-phenyl indans. Thus, there is provided a three-step process for making dixylylpropane from alpha methyl styrene and also a two-step process for making 1,3,3,6-tetramethyl-1-o-xylyl indan from alpha-4-dimethyl styrene. Provided also is a process for preparing 3,3',4,4'-dixylylmethane from a mixture of isomeric dixylylmethanes.
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- New facile synthesis of dimethyl(phenyl)-carbinol and its acetate
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Addition of hydrogen chloride to α-methylstyrene yields a tertiary chloride (II) which on nucleophilic substitution using zinc hydroxide or acetate under optimized conditions affords the carbinol (III) or its acetate.Formation of the dimeric by-products V and VI in the reaction has been suppressed.
- Gurudutt, K. N.,Rao, L. Jagan Mohan,Rao, Sanjay,Srinivas, P.
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p. 468 - 470
(2007/10/02)
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- Potential Dependence of Coupling vs. Reduction in the Reaction between Benzyl Halides and Anion Radicals
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Anion radicals of aromatic and heteroaromatic compounds with reduction potentials in a certain potential interval react with benzyl halides with dissociative electron transfer.The resulting benzyl radical B. may either couple with or be reduced by another anion radical.If the reduction potential of the aromatic compound E0A is more negative than a certain potential Eq1/2 the anion radical A.- will reduce the benzyl radical to the benzyl anion; if E0A is less negative than Eq1/2, coupling between A.- and B. will take place.The relation between Eq1/2, which is defined as the potential at which half of the radicals are reduced and the other half couple, and the standard reduction potential E0(R./R-) for the benzal radicals is discussed.
- Fuhlendorff, Rene,Occhialini, Donatella,Pedersen, Steen U.,Lund, Henning
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p. 803 - 806
(2007/10/02)
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- Electron-Transfer Substitution Reactions: Leaving Groups
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A number of groups that do not participate in SN2 displacement processes are able to function as leaving groups in electron-transfer chain reactions at room temperature; such groups include azide, sulfone, ethers, nitro, quaternary ammonium ions, esters, and thioethers.Even carbanions are able to function as leaving groups as can be seen from fragmentation of carbon-carbon bonds.
- Kornblum, Nathan,Ackermann, Peter,Manthey, Joseph W.,Musser, Michael T.,Pinnick, Harold W.,et al.
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p. 1475 - 1481
(2007/10/02)
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- The Electronic Effect of the Phenylazo and t-Butylazo Groups
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Hammett ?p+-values for arylazo and t-butylazo groups have been determined by measurements of the kinetics of solvolysis of the appropriately substituted arylpropan-2-yl chlorides.They have been found to be considerably more positive than expected and differ significantly from earlier estimates based on the rates of electrophilic attack on azobenzene.An interpretation of the discrepancy has been advanced based on the differing orientations of the azo linkage with respect to the aromatic ring in the transition state.The introduction of methyl groups into positions ortho to the phenylazo and t-butylazo substituents causes a change in character from -I, -R to -I, +R.This is true not only for the solvolysis reaction but also for benzoic acid ionisation.
- Byrne, Christopher J.,Happer, Duncan A. R.,Hartshorn, Michael P.,Powell, H. Kipton J.
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p. 1649 - 1654
(2007/10/02)
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- Working fluid for traction drive
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The working fluid for traction drive comprises (A) a compound having, in a molecule, two decahydronaphthalene rings bonded either directly to each other or to the same or different carbon atoms in an alkane molecule or a compound having, in a molecule, one decahydronaphthalene ring and one cyclohexane ring bonded either directly to each other or to the same carbon atom in an alkane molecule and (B) a compound having two cyclohexane rings bonded either to the terminal carbon atoms of a C2-3 alkane molecule or to the carbon atoms of cyclopentane. The working fluid has a high traction coefficient with stability over a wide range of temperature, especially, in low temperatures.
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- Conformational Dependence of Isotope Effects for Hyperconjugating Methyl Groups. Nonadditivity of NMR Isotope Shifts in Benzylic Ions
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Deuterium substitution in the methyl groups induces long-range downfield shifts in 13C NMR signals of the ortho and para positions of the phenyldimethylcarbenium ion.Similar downfield isotope shifts occur in 19F signals of (p-fluorophenyl)carbenium ions upon deuteration of α-methyl groups.These NMR isotope shifts are analogous to secondary β-deuterium isotope effects on rates and equilibria and arise from hyperconjugative interactions.The effects of substituting entire CD3 groups for CH3 groups are additive, but the effects of deuterium substitution within a methyl group are not additive.The nonadditive behavior is attributed to unequal populations of the possible methyl conformation for partially deuterated methyl groups, so that each C-H(D) bond is not equally involved in hyperconjugation.This interpretation is supported by the observation of an isotope effect on the vicinal 1H-19F coupling constant in the phenylmethylfluorocarbenium ion, PhCFCH3+.
- Forsyth, David A.,Lucas, Peter,Burk, Robert M.
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p. 240 - 245
(2007/10/02)
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- Process for the production of thiolcarbamate compounds
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In the process for the production of a thiolcarbamate compound of the formula STR1 wherein R1 and R2 are as defined in claim, comprising reacting a tertiary halogen compound of the formula STR2 wherein X and R3 are as defined in claim, with a thiolcarbamic acid salt of the formula STR3 wherein M represents a member selected from the group consisting of the alkali metals, ammonium group and immonium group, in an aqueous reaction medium, in the presence of a strong base; the improvement wherein the reaction is carried out under conditions in which the reaction system is adjusted to a pH ranging from about 9 to about 13.
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- Photochemistry of Some Deoxybenzoins in Micellar Solutions. Cage Effects, Isotope Effects, and Magnetic Field Effects
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The photolyses of 1,2-diphenyl-2-methyl-1-propanone (1) and its D-, 13C-, and alkyl-substituted derivatives 2-5 in various micellar solutions have been investigated.It was found that the extent of cage disproportionation to yield benzaldehydes 6 and α-methylstyrenes 7 is enhanced by a factor of about 10 compared to the photolyses in homogeneous organic solvents.The advantage of using micelles rather than homogeneous solutions to enhance the magnitude of magnetic isotope and magnetic field effects on cage disproportionation is demonstrated.The results are interpreted in terms of a mechanism involving the competition between hyperfine-induced intersystem crossing of a triplet radical pair (3RP) to form a singlet radical pair (1RP) and escape of 3RP from the micelle.
- Turro, Nicholas J.,Mattay, Jochen
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p. 4200 - 4204
(2007/10/02)
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- Reactions of Difluoridichloromethane with Hydrocarbons
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The reaction of difluoridichloromethane with different hydrocarbons between 150 deg C and 250 deg C yields the CFCl2-substituted hydrocarbons.Beside it the corresponding chlorides are formed.For the hydrocarbons studied the following sequence of reactivity against difluordichloromethane was found: n-paraffins isoparaffins ca. cycloparaffins alkylaromatics olefines.
- Schmidt, H.,Burtzlaff, Ch.,Masuhr, H.',Ohl, J.,Pehle, W.,et al.
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p. 751 - 760
(2007/10/02)
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- PHOTOCHEMISTRY OF 1,2-DIPHENYL-2,2-DIMETHYL-PROPANONE-1 IN MICELLAR SOLUTIONS. CAGE EFFECTS, ISOTOPE EFFECTS AND MAGNETIC FIELD EFFECTS.
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The cage reaction resulting from photolysis of PhCOC(CH3)2Ph and PhCOC(CD3)2Ph in micellar solution is shown to be subject to substantial magnetic field and magnetic isotope effects.
- Turro, J. Nicholas,Mattay, Jochen
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p. 1799 - 1802
(2007/10/02)
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- Stabilities of Carbonium Ions in Solution. 12. Heats of Formation of Alkyl Chlorides as an Entree to Heats of Solvation of Aliphatic Carbonium Ions
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Heats of formation (ΔHf) of tertiary alkyl chlorides may be calculated from measurements of the heats of hydrochlorination of appropriate olefins at -50 deg C in CH2Cl2.Since many good values for heats of formation of the olefins have been published, the heats of hydrochlorination lead directly to ΔHf for the chlorides, for which few previous values are available.The new data, when combined with previously reported heats of ionization for the chlorides, provide heats of formation for the carbonium ions.Relative values for ΔHf for the carbonium ions are remarkably similar in the gas phase and in SO2ClF, thus supporting the proposal that differential solvation of carbonium ions is small in solvents such as SO2ClF.Because solvation energies are nearly constant for carbonium ions, their relative energies as calculated from quantum theory should apply directly to nonnucleophilic condensed phase values - a situation which is drastically different from that for ammonium or oxonium ions.We have shown previously the close relationship between ionization energies for alkyl chlorides in SO2ClF and their solvolysis rates in ethanol.The present results complete the series of data which are necessary for rigorously relating theoretical calculations of carbonium ion stability to solvolysis reaction rates in solution.Thereby, they help to explain the great success of the carbonium ion theory of organic chemistry.
- Arnett, Edward M.,Pienta, Norbert J.
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p. 3329 - 3334
(2007/10/02)
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