Effect of formaldehyde on the rate constants and composition of the reaction products of dimethylvinylcarbinol and dimethylallyl alcohol in aqueous sulfuric acid solutions

Author(s):  
M. I. Vinnik ◽  
V. S. Malinskii ◽  
G. F. Osipova ◽  
R. S. Ryabova ◽  
O. E. Batalin ◽  
...  

1984 ◽  
Vol 62 (11) ◽  
pp. 2401-2414 ◽  
Author(s):  
Linda M. Druet ◽  
Keith Yates

The acid-catalyzed reactions of acetamide 1, N-tert-butylacetamide 2, and several p-substituted N-benzylacetamides (3 = H, 4 = CH3, 5 = OCH3, 6 = Cl, 7 = NO2) have been studied as a function of acidity and temperature over a wide range of aqueous sulfuric acid solutions (0–91%). Analysis of the reaction products and rate–acidity profiles revealed that four different mechanisms are operative over different acidity regions depending on the structure of the substrate. These are: two A-2 hydrolysis mechanisms with N-acyl fission of the substrate (with participation of one or several water molecules in the rate-determining step); A-1 hydrolysis with N-alkyl fission; and sulfonation, followed by hydrolysis. These conclusions are supported by three complementary and detailed kinetic treatments based on the hydration parameter, transition state activity coefficient, and excess acidity approaches. The acidity domains of each mechanism have been established for each substrate. The mechanistic conclusions are fully supported by the different values of ΔH‡ and ΔS‡ obtained in different regions of acidity.



2005 ◽  
Vol 152 (7) ◽  
pp. E212 ◽  
Author(s):  
Daniel R. Merrill ◽  
Ionel C. Stefan ◽  
Daniel A. Scherson ◽  
J. Thomas Mortimer


2005 ◽  
Vol 5 (6) ◽  
pp. 1577-1587 ◽  
Author(s):  
L. T. Iraci ◽  
R. R. Michelsen ◽  
S. F. M. Ashbourn ◽  
T. A. Rammer ◽  
D. M. Golden

Abstract. Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45-70wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201-252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H*=104-107mol L-1atm-1. H* is inversely dependent on temperature, with ΔH=-45.0±5.4 kJ mol-1 and ΔS=-101±24 J mol-1K-1 for 55-70wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213K, the solubility of HOBr in 45wt% H2SO4 is at least a factor of five larger than in 70wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.







2008 ◽  
Vol 63 (9) ◽  
pp. 603-608 ◽  
Author(s):  
Khamis A. Abbas

The rate constants of the hydrolysis of p-substituted benzonitriles with sulfuric acid solutions (18.2 M to 10 M) have been determined spectrophotometrically at (25.1±0.1) °C. It was found that the catalytic activity of sulfuric acid was strongly inhibited by water. The logarithms of the observed rate constants were correlated with different substituent inductive (localized) and resonance (delocalized) constants. The results of the correlation studies indicated that the rate-determining step of the hydrolysis of benzonitriles in 18.2 M sulfuric acid was the addition of a nucleophile, and the hydrolysis was clearly enhanced by the electron-withdrawing inductive effect, while the rate-determining step of the hydrolysis of p-substituted benzonitriles in 10.0 M sulfuric acid was most probably the protonation of benzonitriles, and the rate constants increased by both electron-donating resonance and inductive effects. A mixture of the two mechanisms most probably occurred in 15.3 to 17.0 M sulfuric acid. HSO4 − rather thanwater most probably acted as nucleophile in the hydrolysis of benzonitriles especially at high concentrations of sulfuric acid solutions.





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