- An Improved Procedure for the Preparation of Very Pure Ethanol-OD
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Changed molar ratio of starting materials and prolonged reaction times in the deuterolysis of tetraethylorthosilicate gave yields of pure (>99.5percent) ethanol-OD (relative to starting D2O) nearly twice of that of a literature procedure. - Keywords: Deuterolysis; Ethanol-OD; Methanol-OD; Tetraethylorthosilicate
- Pesendorfer, Johann,Vierhapper, Friedrich W.
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Read Online
- Aqueous phase hydrodeoxygenation of polyols over Pd/WO3-ZrO2: Role of Pd-WO3 interaction and hydrodeoxygenation pathway
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Aqueous phase processing of biomass derived sugar alcohols is one of the promising routes to convert biomass into fuels and chemicals. Bifunctional catalysts are critical in the aqueous phase hydrodeoxygenation of sugar alcohol. Understanding the interaction between metal and acidic metal oxides as well as the hydrodeoxygenation pathways will help develop more efficient bifunctional catalysts. Here, tungstated zirconia supported palladium catalysts were prepared and further characterized using nitrogen sorption, X-ray diffraction, FT-IR analysis of adsorbed pyridine, CO chemisorption and diffuse reflectance UV-vis. Strong interaction between palladium and WO3 in addition to a synergetic effect of the acidic and metallic sites were found to promote the aqueous phase hydrodeoxygenation of ethylene glycol. H-D exchange experiments using 13C{1H} NMR spectroscopy confirmed that the aqueous phase hydrodeoxygenation follows a dehydration-hydrogenation pathway. The hydrogenation of the dehydration products shifts the dehydration-hydration equilibrium toward the dehydration pathway and leads to highly selective C-O cleavage.
- Liu, Changjun,Sun, Junming,Brown, Heather M.,Marin-Flores, Oscar G.,Bays, J. Timothy,Karim, Ayman M.,Wang, Yong
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p. 103 - 109
(2016/05/11)
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- Isotope Effects in the Solvolysis of Sterically Hindered Arenesulfonyl Chlorides
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Solvent isotope effects in the ethanolysis of sterically hindered arenesulfonyl chlorides ruled out a proton transfer in the rate-determining step and agreed with a SN2 mechanism involving at least a second solvent molecule in the transition state (TS). The lack of a secondary kinetic isotope effect in the o-alkyl groups allows us to disregard the possible contribution of σ-π hyperconjugation. The measured activation parameters are consistent with a SN2 mechanism involving the participation of solvent molecules in the TS, possibly forming a cyclic TS through a chain of solvent molecules.
- Iazykov, Mykyta,Canle L., Moisés,Santaballa, J. Arturo,Rublova, Ludmila
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p. 744 - 750
(2015/10/06)
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- Synthesis, reactivity and catalytic properties of the allenylidene [Ru(C=C=CPh2)Cp(PTA)(PPh3)](CF3SO3) (PTA = 1,3,5-triaza-7-phosphaadamantane)
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The reactivity of [RuCpCl(PTA)(PPh3)] with HC≡CPh and HC≡CC(OH)PPh2 has been studied. The reaction with the phenylacetylene did not provide the desired vinylidene ruthenium complex but as a collateral result the complex [RuCp(DMSO-κS)(PTA)(PPh 3)](CF3SO3) (1) was obtained by reaction of [RuCpCl(PTA)(PPh3)] with Ag(CF3SO3) in DMSO. Reaction of [RuCpCl(PTA)(PPh3)] with HC≡CC(OH)PPh2 provided the Ruthenium(II) diphenyl-allenylidene complex [Ru(C=C=CPh 2)Cp(PTA)(PPh3)](CF3SO3) (2) that was characterized by NMR, IR spectroscopy and elemental analysis. The chemistry of the new diphenyl-allenylidene ruthenium complex has been studied towards a variety of small molecules such as water, O2, n-propylamine, cyclohexylamine and ethanethiol. From the reaction of 2 with the amines and thiol, two isomers are obtained respectively but only one of them could be isolated and characterized. The allenylidene complex was found to be a useful catalyst for the trans-etherification of 1,4-butanedioldivinyl-ether, ethoxyethene and 1-methoxycyclohexa-1,3-diene
- Serrano-Ruiz, Manuel,Lidrissi, Chaker,Ma?as, Sonia,Peruzzini, Maurizio,Romerosa, Antonio
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p. 654 - 661
(2014/03/21)
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- On the solvolysis kinetics of amidoesters derived from β-aminoalcohols
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To better understand reactivity in such systems, fifteen amidoesters derived from β-aminoalcohols were solvolyzed at the ester group in mildly basic methanol-d4. All trials showed pseudo-first-order kinetics by 1H NMR. The rate constants are about 2 to 140-fold larger than those found with simple alkyl esters. The least bulky N-acyl groups generally sponsor the largest rate constants, and strongly so in two cases, but apparently not as a result of lesser steric crowding between the amide and ester groups. Rate constants are also greater for those amidoesters favoring an anti conformation at the amide linkage.
- Hankins, Jamilah N.,Gouws, Michele,Mahajer, Amir,Kim, Ethan S.,Gwaltney, Kevin P.,Haseltine, John
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experimental part
p. 2450 - 2453
(2012/06/01)
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- Structure dependence in the solvolysis kinetics of amino acid esters
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To better understand acyl transfer reactions of oligopeptides, seventeen N-acyl amino acid esters were solvolyzed in mildly basic methanol-d4. All show pseudo-first-order kinetics by 1H NMR. The rate constant varies up to 400-fold with the identity of the amino acid and up to 6200-fold with the identity of the N-acyl group. The impact of the N-acyl group on the rate constant is discussed in terms of crowding, amide conformation, and amide C{double bond, long}O bond character.
- Haseltine, John,Runyon, Jason W.
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scheme or table
p. 3280 - 3283
(2010/07/18)
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- Alkyl radical generation in water under ambient conditions - A new look at the Guareschi reaction of 1897
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(Chemical Equation Presented) Chemical and biochemical significance of a long-forgotten 19th century observation: The hydrocarbon production from quaternary glutarimides on neutralization in water is the consequence of formation of alkyl radicals, which means that it is possible to generate alkyl radicals under very mild conditions. Oxygen trapping competes with hydrogen abstraction (see scheme).
- Nguyen, Bao,Chernous, Katya,Endlar, Daniel,Odell, Barbara,Piacenti, Michela,Brown, John M.,Dorofeev, Alexander S.,Burasov, Alexander V.
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p. 7655 - 7658
(2008/09/18)
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- Catalysis of transesterification reactions by lanthanides - Unprecedented acceleration of methanolysis of aryl and alkyl esters promoted by La(OTf)3 at neutral sspH and ambient temperatures
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La3+ catalysis of the methanolysis of the esters p-nitrophenyl, 2,4-dinitrophenyl, and phenyl acetate (1-3), phenyl benzoate (4), and ethyl, i-propyl, cyclohexyl, and tert-butyl acetate (5, 6a, 6b, 7) was studied at 25°C as a function of sspH and [La(OTf)3]. The active form of the catalyst is attributed to a dimethoxy-bridged dimer of stoichiometry (La3+)2(-OCH3)2, having maximum activity atsspH 8 to 9. For preparative reactions, the active catalyst can be made in situ simply by adding 0.01 equiv of La(OTf)3, and 0.01 equiv of NaOCH3 to a methanol solution containing the ester (1 M). Strong catalysis of methanolysis of both aryl and alkyl esters was observed, although tert-butyl acetate was inert. At sspH 8.5, where the catalyst is maximally active, the transesterification reactions are accelerated by 40 000-fold to 18 000 000-fold in the presence of as little as 5 mM catalyst relative to the background reaction depending on the ester structure. A mechanism for catalysis of transesterification is presented wherein the reactive species is generated by breaking a single La-OCH3 bond of the dimethoxy-bridged dimer to reveal a nucleophilic metal-bound methoxide - Lewis acid La3+ electrophilic pair.
- Neverov, Alexei A.,McDonald, Todd,Gibson, Graham,Brown
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p. 1704 - 1710
(2007/10/03)
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- Analysis of the Mechanism of Photolysis of Methanol-d4 Solutions of Acetylpropionyl Peroxide With the Use of Chemically Induced Dynamic Nuclear Polarization
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On the basis of the effects of chemically induced dynamic nuclear polarization of 1H and 13C and the yields of reaction products, the photolysis of methanol-d4 solutions of acetylpropionyl peroxide is investigated within the. temperature interval 193-333
- Skakovskii, E. D.,Stankevich, A. I.,Lamotkin, S. A.,Tychinskaya, L. Yu.,Avrinskii, G. S.,Rykov, S. V.
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p. 770 - 777
(2007/10/03)
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- Study of the mechanism for the hydrolysis of alkoxy(aryl)(phenyl)-λ6- sulfanenitriles, ArPhS(OR)(?N)
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The hydrolysis of alkoxy(aryl)(phenyl)-λ6-sulfanenitriles in several buffer solutions was found to follow a good pseudo-first-order kinetic equation, giving the corresponding sulfoximides and alcohols (for the case of the hydrolysis of neopentyloxy-λ6-sulfanenitrile, giving a rearranged product, 2-methyl-2-butanol). The dependence of the rate of hydrolysis on the structure of the alkyl group showed the opposite trend to the usual S(N)2 character, i.e. Me +] at pH more than 6.08, and trends to saturate at low pH. According to these kinetic results, a two-step reaction mechanism was proposed which involves a pre-equilibrium protonation on the nitrogen atom of the alkoxy-λ6- sulfanenitriles, followed by a rate-determining C-O bond cleavage via an S(N)2 or S(N)1 mechanism on the alkyl carbon atom depending on the structure of the alkyl group. From a double-reciprocal plot of 1/k(obs) vs. 1/[H+], the pK(a) value and the rate constant of the second reaction of neopentyloxy(diphenyl)-λ6-sulfanenitrile were estimated to be 5.02 and 7.02x10-3 s-1, respectively. The substituent effects on the phenyl group of neopentyloxy(diphenyl)-λ6-sulfanenitrile afforded a large negative p- value (-1.88) for pK(a) and positive one (+1.66) for the second reaction at 25.2 °C. The small negative p-values observed at pH 6.27 for diphenyl(propoxy)-λ6-sulfanenitrile (-0.42) and neopentyloxy(diphenyl)- λ6-sulfanenitrile (-0.26) were found to be the results of a cancellation of those for the opposite trend of the reactions of the pre-equilibrium and the second step. The activation parameters for both the pre-equilibrium and the subsequent reactions were also estimated based on the parameters for the hydrolysis of neopentyloxy(diphenyl)-λ6-sulfanenitrile at pH 6.22 and 2.99. The buffer effect is due to a nucleophilic attack of the buffer base to the alkyl carbon atom of the protonated alkoxy-λ6-sulfanenitriles. The sulfoximide moiety in the protonated λ6-sulfanenitrile is revealed to be a very good leaving group.
- Yoshimura, Toshiaki,Dong, Tiaoling,Fujii, Takayoshi,Ohkubo, Masanori,Sakuta, Mikiko,Wakai, Youko,Ono, Shin,Morita, Hiroyuki,Shimasaki, Choichiro
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p. 957 - 965
(2007/10/03)
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- Acylphosphonate hemiketals - Formation rate and equilibrium. The electron-withdrawing effect of dimethoxyphosphinyl group
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Examination of alcoholic solutions of dimethyl acetylphosphonate (1) and dimethyl benzoylphosphonate (2) by 31P NMR spectroscopy reveals the presence of considerable amounts of hemiketals. Because of the great difference between the 31P chemical shifts of acylphosphonates (ca. 0 ppm) and their hemiketals (17-21 ppm), 31P NMR spectroscopy is a uniquely suitable method for studying the rates and equilibria of hemiketal formation of acylphosphonates with different alcohols. The equilibrium constants Kf, K′f (K′f = Kf[ROH]), pseudo-first-order rate constants k′f, the second order rate constants, kf for hemiketal formation from dimethyl acetylphosphonate with various alcohols, as well as the reverse reaction rate constants, kr to starting materials, were determined. The kinetic isotope effect of 2.8 for the forward reaction kf (EtOH addition) and the backward reaction kr indicates a general catalysis pathway. On the other hand, the calculated values of the enthalpies of activation ΔH? = 10.37 kcal mol-1 (forward), ΔH? = 13.66 kcal mol-1 (backward) and the entropies of activation, ΔS? = -17.25 cal mol-1 K-1 (forward), ΔS? = -9.82 cal mol-1 K-1 (backward) are not in accord with high molecularity of the reaction (1 cal = 4.184 J). Our analysis led to the conclusion that this is probably due to the fact that the transition state is mainly reactant-like with the development of only limited extent of bond formation. Various plausible reaction pathways for hemiketal formation are discussed. In addition, we have calculated the value of 2.65 σ* for the P(O)(OMe)2 group based on proton affinity obtained from heats of formation (ΔHf) of applying the MNDO techniques. The following linear correlation between pKa values and PA values of hemiketals of the form (Me)(R)C(OH)(OCH2X) was developed: pKa = PA - 356.58 + 9.18 [σ*(Me) + σ*(R) + 0.2σ*(X)].
- Katzhendler, Jehoshua,Ringel, Israel,Karaman, Rafik,Zaher, Hisham,Breuer, Eli
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p. 341 - 349
(2007/10/03)
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- A Novel Hybrid System for the Direct Oxidation of Ethane to Acetic and Glycolic Acids in Aqueous Medium
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A combination of platinum(II) ion and metallic platinum is found to oxidise ethane to a mixture of acetic and glycolic acids in aqueous medium in the presence of oxygen; the platinum(II) ion is responsible for the initial C-H activation step leading eventually to the formation of ethanol and ethylene glycol, while metallic platinum catalyses the subsequent air oxidation of the alcohols to the corresponding acids.
- Sen, Ayusman,Lin, Minren
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p. 508 - 510
(2007/10/02)
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- Iridium alkoxide and amide hydride complexes. Synthesis, reactivity, and the mechanism of O-H and N-H reductive elimination
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The ethoxy hydride complex Cp*IrPPh3(OEt)(H) (3, Cp* = η-C5Me5) was prepared from Cp*IrPPh3Cl2 and sodium ethoxide in ethanol. Ethoxide 3 reacted with alcohols to form the alkoxy hydrides Cp*IrPPh3(OR)(H) (R = OCD2CD3, 6a; R = n-Pr, 6b; R = i-Pr; 6c; R = Ph, 6e) and with amines to give the amido hydrides Cp*IrPPh3(NHR)(H) (R = Ph, 8a; R = CH2Ph, 8b). The isopropoxide 6c was characterized by X-ray diffraction (P21/c; a = 11.7943 (13) A?, b = 11.7467 (8) A?, c = 20.3034 (27) A?, β = 96.56 (1)°, V = 2794.5 (9) A?3, 3642 unique data, 2979 for which F2 > 3σ(F2); R = 1.59%, Rw = 2.08%, GOF = 1.378). Irradiation of complex 3 yielded ethanol and the phosphine-cyclometalated complex Cp*Ir(PPh2C6H4)(H) (5a) in cyclooctane or a mixture of 5a and Cp*IrPPh3(Ph)(H) (5b) in benzene. The reaction of 3 with heterocumulenes afforded the products of insertion into the Ir-O bond, Cp*IrPPh3(OCO2Et)(H) (9), Cp*IrPPh3(S2COEt) (10), and Cp*IrPPh3(RNCO2Et) (R = Ph, 11a; R = p-Tol, 11b; R = Me, 11c). Similarly, CS2 underwent insertion into the Ir-N bond of the amido hydrides 8a,b to form Cp*IrPPh3-(S2CNHR)(H) (R = Ph, 12a; R = CH2Ph, 12b). Reaction of MeNCO with 8a, however, gave Cp*IrPPh3(NPhC(O)NHMe)(H) (13b). The reaction of 3 with several two-electron donor ligands yielded ethanol and the Ir(I) compounds Cp*IrPPh3(L) (L = CO, 14; L = C2H4,15; L = CN-t-Bu, 16; L = PPh3, 17; L = PPh2Me, 18). The anilido hydride 8a underwent similar elimination reactions with these ligands to afford 14-18 and aniline; benzylamido hydride 8b reacted with PPh3 to give benzylamine and 17. Saturation kinetics were observed in all cases for the reaction of PPh3 with 3 and 8a,b in toluene, suggesting that these alkoxy and amido hydride compounds reversibly form an intermediate that is trapped by PPh3 to form 17 and alcohol or amine. Additional evidence is provided that supports the ring-slipped species (η3-C5Me5)IrPPh3(X)(H) (X = OEt, NHPh, NHCH2Ph) as the identity of this intermediate.
- Glueck, David S.,Newman Winslow, Linda J.,Bergman, Robert G.
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p. 1462 - 1479
(2008/10/08)
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- THE SYNTHETIC UTILITY OF DIOXYPHOSPHORANES IN ORGANIC SYNTHESIS
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Diethoxytriphenylphosphorane, DTPP, prepared by reaction of triphenylphosphine and diethyl peroxide, is a "hydrolytically active" dioxyphosphorane which promotes mild and efficient cyclodehydration of diols to cyclic ethers in neutral media.Simple 1,2-, 1,4-, and 1,5-diols afford good yields of the cyclic ethers but 1,3-propanediol and 1,6-hexanediol give mainly 3-ethoxy-1-propanol and 6-ethoxy-1-hexanol, respectively, with DTPP.Tri- and tetra-substituted 1,2-diols afford the relatively stable 1,3,2-dioxaphospholanes in the presence of DTPP and the reaction conditions dictate whether epoxides, ketones, or allylic alcohols are obtained.
- Robinson, Philip L.,Kelly, Jeffery W.,Evans, Slayton A.
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- HOMOLOGATION WITH CO+H2 OF ETHYL ORTHOFORMATE IN THE PRESENCE OF RUTHENIUM CATALYSTS: A STEPWISE HYDROGENATION AND CARBONYLATION REACTION
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The reaction of ethyl orthoformate with CO+H2 (P 10-15 MPa) in the presence of ruthenium carbonyl iodide catalysts at temperatures of 130-200 deg C has been studied.Products of hydrogenation, carbonylation and homologation of the CH, Et and EtO moieties of the ester are formed, indicating that the catalyst can activate the substrate in three ways.Diethoxymethane was the main product at lower temperatures, whereas methyl ethyl ether, methanol, and ethyl propionate predominate at higher temperatures.The formation of significant amounts of diethyl carbonate and diethoxyethane indicates the intermediate formation of EtO-Ru derivatives.Results of experiments with CO+D2 suggest a step-wise process of hydrogenation and carbonylation of the substrate, and shed new light on the mechanism of activation of esters by ruthenium carbonyl iodide catalysts.
- Braca, G.,Galletti, A. M. Raspolli,Sbrana, G.,Lazzaroni, R.
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p. 107 - 116
(2007/10/02)
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- Onium Ylide Chemistry. 4. Alkylhalonium Methylides
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Alkylhalonium methylides were generated by two independent routes, proving their formation through derived product analysis.The reaction of singlet methylene, produced by photolysis of diazomethane, with methyl and ethyl halides gives in competition with C-H insertion evidence of methylenation of halogen atom, i.e., alkylhalonium methylide formation.The unstable halonium methylides are immediatly protonated or alkylated in the reaction medium to give dialkylhalonium ions which then undergo cleavage to the corresponding alkyl halides.Methyliodonium methylide was also generated via the deprotonation of dimethyliodonium hexafluoroantimonate with sodium hydride in competition with the expected methylation of fluoride and hydride, giving the major products.Subsequent methylation of the methyliodonium methylide by excess dimethyliodonium ion gives methylethyliodonium ion followed by cleavage leading to the formation of ethyl halides and via hydride reduction to ethane, respectively.Attempted formation of alkylhalonium methylides via fluoride cleavage of methylhalonium hexafluoroantimonates was unsuccessful due to ready disproportionation of the halonium ions.
- Olah, George A.,Doggweiler, Hans,Felberg, Jeff D.
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p. 4975 - 4978
(2007/10/02)
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- A New Method for Obtaining Isotopic Fractionation Data at Multiple Sites in Rapidly Exchanging Systems
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A new method for rapidly and conveniently obtaining isotopic fractionation factors in dilute aqueous solutions of compounds containing rapidly exchanging OH, NH, and SH groups is described.Shifts in the positions of NMR peaks for spectroscopically observable nuclei induced by isotopic substitution are the basis of this procedure which has the unique capability of separately measuring the isotopic exchange constants simultaneously for several different groups in the same molecule.The results for a series of alcohols, amines, thiols, phenols, acids, and amides with use of 13C NMR spectroscopy are reported.Atypically low values of Kfrac are observed in several cases, indicating that there are strong internal hydrogen bonds in competition with those to water, yielding conformational information.
- Jarret, Ronald M.,Saunders, Martin
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p. 2648 - 2654
(2007/10/02)
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- Thermoneutral Isotope Exchange Reactions of Cations in the Gas Phase
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Rate constants have been measured for reactions of the type AD2+ + MH --> MD + ADH+, where AD2+ is CD3CND+, CD3CDOD+, (CD3COCD3)D+, or (C2D5)2OD+ and the MH molecules are alcohols, acids, mercaptanes, H2S, AsH3, PH3, or aromatic molecules.Rate constants are also presented for the reactions ArHD+ + D2O --> ArDD+ + HDO, where ArHD+ is a deuteronated aromatic molecule and ArDD+ is the same species with a D atom incorporated on the ring.In all but two cases, the competing deuteron transfer is sufficiently endothermic that it cannot be observed under the conditions of the ICR experiments at 320 - 420 K.The efficiencies of the isotope exchange reactions are interpreted in terms of estimated potential surface cross sections for the reactions AD2+ + MH --> 2+*MH> --> +> --> +*MD> --> ADH+ + MD.When the formation of the +> complex is estimated to be thermoneutral or slightly endothermic, the isotope exchange process is inefficient (probability of a reactive collision 2+*MH> --> +> is exothermic.For most of the systems, trends in reaction efficiency appear to be related to factors such as dipole moments of reactant species (or for aromatic compounds, the electron-donating or -withdrawing properties of ring substituents) which influence the relative orientation of the two reactant species in the complex.
- Ausloos, P.,Lias, S. G.
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p. 3641 - 3647
(2007/10/02)
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- Vapour Pressure Study of the Deuterium Exchange Reaction in Methanol-Ethanol Systems: Equilibrium Constant Determination
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The equilibrium constant of the reaction: CH3OH(l) + C2H5OD(l) --> CH3OD(l) + C2H5OH(l) is obtained from vapour pressure measurements on methanol+ethanol systems.The value obtained, 1.03 +/- 0.01 at 298 K, is in good agreement with that calculated independently from previously reported vapour pressure studies of water+methanol systems and water+ethanol systems.Vapour pressures at 298.15 K are reported for the systems CH3OH+C2H5OH, CH3OH+C2H5OD, CH3OD+C2H5OH and CH3OD+C2H5OD.Molar excess Gibbs functions are obtained from these vapour pressures.
- Kooner, Zorawar S.,Fenby, David V.
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p. 1943 - 1946
(2007/10/02)
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