3315-60-4Relevant academic research and scientific papers
Concurrent Methoxide Ion Attack at the 5- and 7-Carbons of 4-Nitrobenzofurazan and 4-Nitrobenzofuroxan. A Kinetic Study in Methanol
Terrier, Francois,Chatrousse, Alain-Pierre,Millot, Francois
, p. 2666 - 2672 (1980)
In methanolic solution,methoxide ions attack both the 5- and 7-carbons of 4-nitrobenzofurazan (5) and 4-nitrobenzofuroxan (8) to give the Meisenheimer-type complexes 6, 9 and 7, 10.The kinetics of the interactions have been studied by the stopped-flow method.The formation of the 5-methoxyl adducts 6 and 9 is found to always precede that of the thermodynamically more stable 7-methoxyl isomers 7 and 10.The results indicate that the para-like 4-nitro group is more efficient than the furazan and the furoxan rings in delocalizing the negative charge in 7 and 10.The kinetic and thermodynamic parameters Δ H0, Δ S0, Δ H(excit.), and Δ S(excit.) or the various reactions have been determined.It appears that only a large positive entropy change, Δ S0 (about +80 J/mol*K), is responsible for both the formation and the greater stability of the 7-methoxyl complexes 7 and 10 as compared to that of their 5-methoxyl analogues.Stabilization of 7 and 10 by association of the 4-nitro group with the potassium counterion is suggested.
Acceleration of the methanolysis of phosphate diesters promoted by La(OTf)3 - The analysis of non-integer s spH/rate profiles resulting from changes in metal ion speciation
Gibson, Graham T.T.,Neverov, Alexei A.,Teng, Allen Chun-Tien,Brown
, p. 1268 - 1276 (2007/10/03)
In a previous publication (A.A. Neverov and R.S. Brown. Inorg. Chem. 40, 3588 (2001)) we reported very effective catalysis of the methanolysis of some phosphate diesters (methyl p-nitrophenyl phosphate (1), bis(p-nitrophenyl) phosphate (2), and diphenyl p
Acidity, basicity, and the stability of hydrogen bonds: Complexes of RO- + HCF3
Chabinyc, Michael L.,Brauman, John I.
, p. 10863 - 10870 (2007/10/03)
Ion-molecule complexes of RO- (R = Me, Et, i-Pr) and HCF3 have been studied with Fourier transform ion cyclotron resonance spectrometry. The RO- complexation energies with HCF3 were measured relative to RO-·H2O. These complexes, [ROHCF3]-, have complexation energies on the order of -20 kcal/tool and have low deuterium fractionation factors and are, therefore, hydrogen bonded. The structure of the complexes was studied by isotopic equilibrium experiments and ab initio calculations. All of the complexes studied have the structure RO-·HCF3 even when HCF3 is a stronger acid than ROH. The structure of the complexes can be understood through electrostatic arguments rather than the difference in acidity between the ion and neutral.
Gas-Phase Nucleophilic Displacement Reactions
Olmstead, William N.,Brauman, John I.
, p. 1653 - 1662 (2007/10/03)
Displacement reactions of each of a variety of anionic nucleophiles reacting with each of a variety of neutrals have been studied by pulsed ion cyclotron resonance (ICR) spectroscopy.Rate constants for these reactions are interpreted in terms of a three-step reaction sequence.RRKM calculations are used to obtain information about the energy of transition states.The origin of the barrier to reaction in solution is discussed.
Kinetic analysis of elementary steps in nucleophilic vinylic substitution reactions of α-nitro-β-X-stilbenes (X = OCH2CF3, OCH3, NO2) with various nucleophiles.
Bernasconi, Claude F.,Schuck, David F.,Ketner, Rodney J.,Weiss, Minda,Rappoport, Zvi
, p. 11764 - 11774 (2007/10/02)
Rate constants of elementary steps in the addition-elimination mechanism of nucleophilic vinylic substitutions (SNV) were determined by studying the following reactions in 50% Me2SO-50% water at 20 °C: (1) α-nitro-β-(2,2,2-trifluoroethoxy)stilb
Reaction Rates of Trimethylethoxysilane and Trimethylmethoxysilane in Alkaline Alcohol Solutions
Jaeglid, Ulf,Lindqvist, Oliver
, p. 887 - 891 (2007/10/02)
The kinetics of the reaction (CH3)3SiOC2H5 + CH3O- (CH3)3SiOCH3 + C2H5O- have been investigated in both directions by means of FTIR spectroscopy.To obtain k1, trimethylethoxysilane was reacted with methoxide in a metha
Kinetics of reactions of hydroxide ion and water with β-X-substituted α-nitrostilbenes (X = Cl, I, SEt, OMe, SCH2CH2OH) in 50% Me2SO-50% water. Search for the intermediate in nucleophilic vinylic substitution
Bernasconi, Claude F.,Fassberg, Julianne,Killion Jr., Robert B.,Schuck, David F.,Rappoport, Zvi
, p. 4937 - 4946 (2007/10/02)
The hydrolysis of Ph(LG)C=Cph(NO2) (4-LG, Lg = Cl, I, Set, Ome) in basic solution yields the anion of 1,2-diphenyl-2-nitroethanone, PhC(=O)C(=NO2-)Ph (8-), by the addition-elimanation mechanism of nucleophilic v
The gas-phase elimination reaction of 3-methoxycyclohexene: Regiochemistry
Rabasco, John J.,Kass, Steven R.
, p. 4077 - 4080 (2007/10/02)
Gas-phase elimination reactions of deuterium labeled 3-methoxycyclohexenes have been investigated. 1,4-Elimination is heavily favored over 1,2-elimination when strong bases such as hydroxide and amide are used. The 1,2-pathway becomes more competitive when weaker bases such as methoxide are employed, and the mechanism shifts from E1 cB to E2.
KINETICS AND MECHANISM OF SOLVOLYSIS OF N-ARYL SULFURIC DIAMIDES
Kavalek, Jaromir,Kralikova, Ulrika,Machacek, Vladimir,Sedlak, Milos,Sterba, Vojeslav
, p. 202 - 222 (2007/10/02)
The methanolysis and hydrolysis kinetics have been studied with the following sulfuric diamide derivatives: N-methyl-N-phenyl- (IIIa), N-methyl-N-(4-methoxycarbonylphenyl)- (IIIb), N-(4-methoxycarbonylphenyl)- (IIIc), N-methyl-N-(2-methoxycarbonylphenyl)- (IIId), N-(2-methoxycarbonylphenyl)- (IIIe), and N-methyl-N-(2,4-dibromophenyl)- (IIIf).The solvolyses of the neutral substrates IIIa and IIIb proceed by the addition-elimination mechanism.In the presence of the solvent lyate ions the solvolyses go by the E1cb mechanism.The solvolyses of the conjugated bases ofcompounds IIIa and IIIb are subject to general acid catalysis, the effects of the ring substituents being opposite to those in the addition-elimination mechanism.The solvolyses of compounds IIId and IIIf exhibit a distinct catalytic effect of neighbouring group; the reaction goes via a reactive intermediate, the transformation of the intermediate into the solvolysis product being subject to general acid and base catalysis.
Study of Reactions Leading to Sulfine Formation. 3. Competition of Reaction Pathways in the Reaction of Methoxide Ion with Methyl 1-Naphthylmethanesulfinates
Kice, John L.,Lotey, Harvinder
, p. 3596 - 3602 (2007/10/02)
In CD3O1-/CD3OD methyl 1-naphthylmethanesulfinates, NpCH2S(O)OCH3 (2), undergo both exchange of CH3O by CD3O by substitution at the sulfinyl group and elimination to form the sulfine, NpCH=S=O.With use of methyl (2-methoxy-1-naphthyl)methanesulfinate (2a) it has been shown that formation of the sulfine takes place by an (E1cB)irrev mechanism.The rates of substitution (ks) and elimination (ke) of a series of 2 have been determined in CD3O1-/CD3OD by 1H NMR spectroscopy, and the effect of several reaction variables on the competition between substitution and elimination has been examined.Salient results are as follows: (1) the rate of elimination is markedly increased by the presence of electron-withdrawing substituents on the aromatic ring, but the rate of substitution is increased only modestly by the same substituents; (2) substituents at the 2-position of the naphthyl group cause a large decrease in ks (steric hindrance to substitution at S=O) but have little effect on ke (elimination rate not sensitive to steric requirements of ortho substituents); (3) the activation energy for elimination is almost 9 kcal/mol greater than the activation energy for substitution.This large difference in activation energy contrasts with the 1-2 kcal/mol difference for elimination vs substitution found14 with alkyl halides.
