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1.
Data on the kinetics, selectivity, kinetic isotope effect, and the effect of the acidity of the medium on the rate of the
reactions of benzene and alkylbenzenes in sulfuric acid (59–78 wt.% H 2SO 4) solutions of 1-adamantanol at 30 °C indicate that the direct reagents are the adamantyl carbocations (Ad +) that alkylate the arenes. The ortho positions of the benzene ring are not accessible on account of steric hindrances. The
rate of attack by the Ad + cation on the accessible para and meta positions of the ring is controlled by the formation of a σ complex.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 14–18, January–February, 2006. 相似文献
2.
For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C 6H 4—OC 11H 23)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods.
It has been found that in o-xylene at concentrations of Zn(4—O—CO—C 6H 4—OC 11H 23)Pc higher than 6×10 −4 mol⋅L −1
π– π dimers species are formed ( λ
max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C 6H 4—OC 11H 23)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes.
Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C 6H 4—OC 11H 23)Pc—DABCO—Zn(4—O—CO—C 6H 4—OC 11H 23)Pc sandwich dimers ( λ
max= 675 nm). 相似文献
3.
The effect of the acidity of the medium on the hydroxylation and nitration of alkanes (RH) in 90–98% H 2SO 4 at 25°C is described quantitatively by a model taking account of the thermodynamic activity of the RH, H 2O, and HSO 4- particles. It was concluded that in the transition states the reagents H 3O 2+HSO 4- and NO 2+ HSO 4- are present as HO + and NO 2+ ions without the bases H–O and HSO 4-, the alkanes are present without hydrophobic shells, and the initial reaction products are ROH 2+ and RNO 2H +. 相似文献
4.
The positive APCI-mass spectra in air of linear ( n-pentane, n-hexane, n-heptane, n-octane), branched [2,4-dimethylpentane, 2,2-dimethylpentane and 2,2,4-trimethylpentane ( i-octane)], and cyclic (cyclohexane) alkanes were analyzed at different mixing ratios and temperatures. The effect of air humidity
was also investigated. Complex ion chemistry is observed as a result of the interplay of several different reagent ions, including
atmospheric ions O 2+•, NO +, H 3O +, and their hydrates, but also alkyl fragment ions derived from the alkanes. Some of these reactions are known from previous
selected ion/molecule reaction studies; others are so far unreported. The major ion formed from most alkanes (M) is the species
[M − H] +, which is accompanied by M +• only in the case of n-octane. Ionic fragments of C
n
H 2n
+1/+ composition are also observed, particularly with branched alkanes: the relative abundance of such fragments with respect
to that of [M − H] + decreases with increasing concentration of M, thus suggesting that they react with M via hydride abstraction. The branched
C 7 and C 8 alkanes react with NO + to form a C 4H 10NO + ion product, which upon collisional activation dissociates via HNO elimination. The structure of t-Bu +(HNO) is proposed for such species, which is reasonably formed from the original NO +(M) ion/molecule complex via hydride transfer and olefin elimination. Finally, linear alkanes C 5–C 8 give a product ion corresponding to C 4H 7+(M), which we suggest is attributed to addition of [M − H] + to C 4H 8 olefin formed in the charge-transfer-induced fragmentation of M. The results are relevant to applications of nonthermal plasma
processes in the fields of air depuration and combustion enhancement. 相似文献
5.
We have determined the parameters of the Arrhenius equation ( E, log A) for reactions between
\text NO2+ {\text{NO}}_2^{+} ions and C 3-C 8 alkanes in HNO 3–93 wt.% H 2SO 4 solutions at 277–353 K, and we have also estimated the activation parameters E
j
, log A
j
for secondary and tertiary C—H bonds of these alkanes. We show that the following compensation relations are satisfied: E = 2.3 R βlog A + C with isokinetic temperature β = 360 ± 65 K, and also E
j
=2.3 Rβ
j
log A
j
+ C
j
, for secondary C—H bonds, β 2 =300 ± 60, and for tertiary C—H bonds, β 3 =310 ± 50. 相似文献
6.
We have determined the differences in the parameters log A and E of the Arrhenius equations for the kinetic isotope effect (KIE) ( c-C 6H 12/ c-C 6D 12) and the 5/6 effect ( c-C 5H 10/ c-C 6H 12) in reactions of the C—H bonds of cycloalkanes with adamantyl (Ad +) carbocations (1-adamantanol in 92.8% H 2SO 4, 40-97 °C). We have established the compensation relations between log A and E for the kinetic isotope effect and the 5/6 effect for anthracene (AH +), hydroxymethyl (CH 2OH +), Ad + carbocations and the hypothetical "infinitely strong reagent," supporting a hydride transfer mechanism in such reactions. 相似文献
7.
Due to hydrogen bonding, bis(18-crown-6) stilbene forms 1 : 1, 1 : 2, and 2 : 2 complexes with H 3N +(CH 2)
n
NH 3
+ 2ClO 4
− salts ( n = 2—10, 12). The length of the polymethylene chain in the diammonium ions affects the phototransformation direction of stilbene
and the composition of the products. In the 2: 2 bispseudosandwich complexes with relatively short alkanediammonium ions ( n = 2—4), the stereoselective reaction of [2+2] photocycloaddition proceeds to form mainly the rctt-isomer of the cyclobutane derivative. The structure of rctt-cyclobutane derivative as a complex with H 3N +(CH 2) 4NH 3
+2ClO 4
- was confirmed by X-ray diffraction analysis. 相似文献
8.
The oxidation kinetics of the 2-aminomethylpyridineCr III complex with periodate in aqueous solution were studied and found to obey the rate law:Rate = [Cr III] T [IO 4
-]{k 1K 2 + k 2 K 1 K 3/[H +]}/{1+K 1/[H +] + k 2[IO 4
-]+K 1K 3/[H +][IO 4
-]} where K
1, K
2 and K
3 are the deprotonation of [Cr(L) 2(H 2O)] 3+ and pre-equilibrium formation constants for [(L) 2—Cr—OIO 3] 2+ and [(L) 2—Cr—OH—OIO 3] + precursor complexes respectively. An inner-sphere mechanism was proposed. The effect of Cu 2+ on the oxidation rate was studied over the (1.0–9.0) × 10 −5 mol dm −3 range. The reaction rate was found to be inversely proportional to the Cu 2+ concentration over the range studied.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Oxidation of the cyclohexadienyl complex Fe(η 5-C 5H 5)(1-5-7 5-6- exo-C 5H 5-C 6H 6) (2) by (Ph 3C)PF 6 (CH 2Cl 2, from −30 to +20 °C) occurs as two concurrent processes: elimination of an H atom from the cyclohexadienyl ligand and replacement
of an H atom in the cyclopentadienyl ring by a CPh 3 fragment. A mixture of cationic complexes [Fe(η 5-C 5H 5) (η 6-Ph-C 5H 5] + (1 +) and [Fe(η 5-C 5H 4CPh 3) (η 6-Ph-C 5H 5] + (4 +) ( 4
+) with PF 6
− anions is obtained. Deprotonation of the mixture of 1 + and 4 + complexes under the action of Bu
t
OK in m-xylene followed by boiling of the reaction mixture gives phenylferrocene (7) as the product of η 6:η 6 haptotropic rearrangement.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, NO. 5, pp. 1045–1047, May, 1997. 相似文献
10.
Visible light irradiation of the [(η-C 6H 7)Fe(η-C 6H 6)] + cation ( 1) in CH 2Cl 2 in the presence of alkyl-substituted benzenes results in arene exchange forming the [(η 5-C 6H 7)Fe(η-C 6R 6)] + cations ( 2a–d: C 6R 6 is toluene, p-xylene, mesitylene, and durene). The mixed bis(arene) [(η-C 6H 6)Fe(η-C 6R 6)] 2+ iron complexes ( 3a–d) were synthesized by hydride ion abstraction from 2a–d by [Ph 3C] +.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1864–1865, September, 2007. 相似文献
11.
OH + is an extraordinarily strong oxidant. Complexed forms (L? OH +), such as H 2OOH +, H 3NOH +, or iron–porphyrin‐OH + are the anticipated oxidants in many chemical reactions. While these molecules are typically not stable in solution, their isolation can be achieved in the gas phase. We report a systematic survey of the influence on L on the reactivity of L? OH + towards alkanes and halogenated alkanes, showing the tremendous influence of L on the reactivity of L? OH +. With the help of with quantum chemical calculations, detailed mechanistic insights on these very general reactions are gained. The gas‐phase pseudo‐first‐order reaction rates of H 2OOH +, H 3NOH +, and protonated 4‐picoline‐ N‐oxide towards isobutane and different halogenated alkanes C nH 2n+1Cl ( n=1–4), HCF 3, CF 4, and CF 2Cl 2 have been determined by means of Fourier transform ion cyclotron resonance meaurements. Reaction rates for H 2OOH + are generally fast (7.2×10 ?10–3.0×10 ?9 cm 3 mol ?1 s ?1) and only in the cases HCF 3 and CF 4 no reactivity is observed. In contrast to this H 3NOH + only reacts with tC 4H 9Cl ( kobs=9.2×10 ?10), while 4‐CH 3‐C 5H 4N‐OH + is completely unreactive. While H 2OOH + oxidizes alkanes by an initial hydride abstraction upon formation of a carbocation, it reacts with halogenated alkanes at the chlorine atom. Two mechanistic scenarios, namely oxidation at the halogen atom or proton transfer are found. Accurate proton affinities for HOOH, NH 2OH, a series of alkanes C nH 2n+2 ( n=1–4), and halogenated alkanes C nH 2n+1Cl ( n=1–4), HCF 3, CF 4, and CF 2Cl 2, were calculated by using the G3 method and are in excellent agreement with experimental values, where available. The G3 enthalpies of reaction are also consistent with the observed products. The tendency for oxidation of alkanes by hydride abstraction is expressed in terms of G3 hydride affinities of the corresponding cationic products C nH 2n+1+ ( n=1–4) and C nH 2nCl + ( n=1–4). The hypersurface for the reaction of H 2OOH + with CH 3Cl and C 2H 5Cl was calculated at the B3 LYP, MP2, and G3 m* level, underlining the three mechanistic scenarios in which the reaction is either induced by oxidation at the hydrogen or the halogen atom, or by proton transfer. 相似文献
12.
The structure of aqua complexes of alkali metal ions Me +(H 2O)
n
, n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH 3) 2PhO − selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me +(H 2O)
n
, n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies
of binding of alkali metal hydrated cations with (CH 3) 2PhO − depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and
rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH 3) 2PhO − decreased in the series Li + > Na + > K + > Rb + > Cs + as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with
respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution
to the phenol phase compared with the stage of binding with ion exchange groups. 相似文献
13.
Hydrogen bromide is known to inhibit the bromination of aromatic substrates (ArH), either by fixing up bromine as HBr 3 or ArH as ArH · HBr. However, there is catalysis by HBr in the bromination of mesitylene in acetic acid. The bromination of o-xylene in acetic acid in the dark is found to be autocatalytic, and the reaction is overall third order, first order in o-xylene with the orders in Br 2 and HBr depending on the concentrations. A composite rate expression involving Br 2 and HBr as electrophiles has been proposed and verified using iodine bromide as a catalyst where the orders are one in each of the reactants, irrespective of the concentrations used. 相似文献
14.
The dimeric bis(quaternaryammonium bromide) surfactants, [Br −(CH 3) 2N +(C
m
H 2
m
+1)—(CH 2)
s
—(C
m
H 2
m
+1)N +(CH 3) 2Br −, s = 2, 3 and m = 4, 6, 10 and 12, s = 6 and m = 8, 10, 12], have been synthesized and the phase maps of the sm6-8-water, sm6-10-water and sm6-12-water binary systems have
been determined (sm6-8 implies s = 6, m = 8). In order to examine the molecular structures of these solid samples and of their dimeric surfactant-water binary systems,
Raman spectra of the simple dimeric surfactants, sm2-4 and sm3-4, in which crystal structures of the trans- and cis-type conformations
have been determined by single-crystal X-ray diffraction analysis, have been investigated, and Raman bands characteristic
of these skeletal structures were found in the skeletal deformation region. On the basis of these characteristic Raman bands
for the two conformations, it has been concluded that the dimeric surfactants, sm6-8, sm6-10 and sm6-12 also take up a cis-type
conformation in the crystalline state. Furthermore, it has been found that the Raman bands in the C—H stretching, skeletal
stretching and CH 2 scissoring regions are sensitive to phase structure.
Received: 21 July 1998 Accepted in revised form: 9 November 1998 相似文献
15.
The extraction of the pertechnetate anion has been investigated in the systems tributylphosphate (TBP)—solvent (carbon tetrachloride,
n-heptane, chloroform)—metal salt (uranyl nitrate and chloride, thorium nitrate)—ammonium salt. In the absence of a metal,
the solvates HTeO 4. iTBP (i=4) are extracted, while in the presence of uranium and thorium, the distribution of technetium corresponds to the
formation of the mixed complexes: UO 2(NO 3)(TeO 4)·2TBP, UO 2Cl(TcO 4)·2TBP and Th(NO 3) 3 (TcO 1)·2TBP. The effective constants of the reactions H ++TcO
4
−
+i(TBP) org←(HTcO 1·iTBP) org, and (ML n·2TBP) org+TcO
4
−
←(ML n−1TcO 4·2TBP) org+L were established in the above systems. The extraction of pertechnetate ion is more effective when it is coordinated to
a cation solvated by TBP than the extraction in the form of pertechnetate acid solvated by TBP. 相似文献
16.
The enthalpies of solvation of four geometric isomers of 2,5-dimethyl-1-phenyl-1-thioxophosphorinan-4-one in chloroform, nitrobenzene,
and methanol were calculated using the enthalpies of vaporization of the isomers determined by the modified Solomonov—Konovalov
method from the enthalpies of solution of the compounds in CCl 4 and p-xylene and molar refractions. The enthalpies of formation (Δ H
f
o) of the isomers in the condensed and gas phase were assessed in the framework of Benson's group additivity scheme by summing
the Δ H
f
o values for phosphacycloketone fragments obtained from molecular mechanics calculations with the contributions of the phenyl
group and S atom attached to the P atom.
Published in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1533–1536, September, 2000. 相似文献
17.
Excess molar enthalpies, H
E,
for the binary mixtures { p-xylene+(1– x) octane}, { x
p-xylene+(1– x)
diethyl carbonate}, { x octane+(1– x) diethyl carbonate} and the corresponding ternary
system { x
1
p-xylene+ x
2
octane+(1– x
1– x
2) diethyl carbonate} have
been measured by using a Calvet microcalorimeter at 298.15 K under atmospheric
pressure. The experimental H
E
values are all positive for the binary and ternary mixtures over the entire
composition range. 相似文献
18.
The complexation reactions between Ag +, Hg 2+ and Pb 2+ metal cations with aza-18-crown-6 (A18C6) were studied in dimethylsulfoxide (DMSO)–water (H 2O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stoichiometry
of the complexes in most cases is 1:1(ML), but in some cases 1:2 (ML 2) complexes are formed in solutions. A non-linear behaviour was observed for the variation of log K
f of the complexes vs. the composition of the binary mixed solvents. Selectivity of A18C6 for Ag +, Hg 2+ and Pb 2+ cations is sensitive to the solvent composition and in some cases and in certain compositions of the mixed solvent systems,
the selectivity order is changed. The values of thermodynamic parameters (Δ H
co, Δ S
co) for formation of A18C6–Ag +, A18C6–Hg 2+ and A18C6–Pb 2+ complexes in DMSO–H 2O binary systems were obtained from temperature dependence of stability constants and the results show that the thermodynamics
of complexation reactions is affected by the nature and composition of the mixed solvents. 相似文献
19.
Interaction of immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene with Na+, Cs+, and NH4
+ ions and organic cations
The equilibrium in the system water—electrolyte—cross-linked polymer containing immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene
was studied. Immobilized calixarene 1 was shown to form 1∶1, 1∶2, 1∶3, and 1∶4 compounds with inorganic cations (Na +, Cs +, and NH 4
+), and with organic cations (hexamethylen-tetramine and β-diethylaminoethyl p-aminobenzoate) 1∶1 compounds are formed. The affinity of immobilized calixarene 1 increases in the series of cations: hexamethylenetetramine <Na +, Cs +, NH 4
+<β-diethylaminoethyl p-aminobenzoate.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2214–2216, November, 1998. 相似文献
20.
The photoionization and dissociative photoionization of m-xylene (C8H10) were researched by using synchrotron radiation vacuum ultraviolet (SR-VUV) and supersonic expanding molecular beam reflectron time-of-flight mass spectrometer (RFTOF-MS) system. The photoionization efficiency spectra (PIEs) of parent ion C8H10+ and main fragment ions C8H9+ and C7H7+ were observed, and the ionization energy (IE) of m-xylene and appearance energies (AEs) of main fragment ions C8H9+ and C7H7+ were determined to be 8.60 ± 0.03 eV, 11.76 ± 0.04 eV and 11.85 ± 0.05 eV, respectively. Structures of reactant, transition states (TSs), intermediates (INTs), and products involved in two dominant dissociation channels were optimized at the B3LYP/6-311++G(d,p) level, and the relative energies were calculated at the G3 level. Based on the results, two major dissociative photoionization channels, C7H7++CH3 and C8H9++H were calculated at the B3LYP/6-311++G(d,p) level. On the basis of theoretical and experimental results, the dissociative photoionization mechanisms of m-xylene were proposed. The C–H or C–C bond dissociation and hydrogen migration are the main processes in the dissociation channels of m-xylene cation. 相似文献
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