scholarly journals Kinetics, stoichiometry and mechanism in the bromination of aromatic heterocycles. IV. Aqueous bromination of Imidazo[1,2-a]pyridine

1974 ◽  
Vol 27 (11) ◽  
pp. 2349 ◽  
Author(s):  
BE Boulton ◽  
BAW Coller
Keyword(s):  
Aqueous Solution ◽  
Rate Coefficient ◽  
Acetate Buffer ◽  
Acidic Aqueous Solution ◽  
Aromatic Heterocycles

The reaction of imidazo[l,2-a]pyridine with bromine has been studied in dilute acidic aqueous solution at 25�C. The bimolecular rate coefficient for attack by Br2 on the molecular substrate at the 3-position is found to be K�bi = 1.30(� 0.05) x 109 dm3 mol-l s-l We find pK.(imidazo[l,2-a]pyridine-H+, aq., 25�C) = 6.65 and pK,(3-bromoimidazo[l,2-alpyridine-H+, aq.,25�C) = 4.95. The latter compound reacts with bromine in aqueous acetate buffer at pH4.

Kinetics and Mechanism of the Thermal Decomposition of Hexaamminecobalt(III) and Aquopentaamminecobalt(III) Ions in Acidic Aqueous Solution

1974 ◽  
Vol 52 (15) ◽  
pp. 2751-2759 ◽  
Author(s):  
Anthony Martin Newton ◽  
Thomas Wilson Swaddle
Keyword(s):  
Aqueous Solution ◽  
Thermal Decomposition ◽  
Rate Coefficient ◽  
Initial Step ◽  
Hydrogen Ion ◽  
Minor Amount ◽  
Acidic Aqueous Solution ◽  
First Order ◽  
Independent Path ◽  
A Minor

The initial step in the thermal decomposition of Co(NH3)63+ in acidic aqueous solution is the replacement of NH3 by H2O, which occurs by a hydrogen-ion independent path, first order in complex, with rate coefficient k1 = 7.9 × 10−5 s−1 (140.4°), ΔH* = 36.6 kcal mol−1 and ΔS* = 10.7 cal deg−1 mol−1 in 0.1 M HClO4. For Co(NH3)5OH23+, there is a similar initial aquation path with k1 = 12.6 × 10−5 s−1 (140.6°), ΔH* = 41.9 kcal mol−1 and ΔS* = 24 cal deg−1 mol−1 and also a path first order in complex but inverse first order in [H+] with k2′ = 6.2 × 10−1 M s−1 (140.6°), ΔH* = 43.5 kcal mol−1 and ΔS* = 26.7 cal deg−1 mol−1 in perchlorate media of ionic strength 1.0 M. The effects of electrolyte type and concentration on the rates of these reactions have been examined. Subsequent aquation steps are relatively rapid because of the predominance of inversely [H+]-dependent pathways and are followed by redox to Co(H2O)62+, NH4+, N2, N2O, and a minor amount of O2. A mechanism involving OH and NH2 radicals is proposed for the redox step.

Oxidation of alkyl thiocyanates by peroxomonosulphate in acidic aqueous solution

1971 ◽  
Vol 24 (12) ◽  
pp. 2481 ◽  
Author(s):  
GJ Bridgart ◽  
IR Wilson
Keyword(s):  
Aqueous Solution ◽  
Rate Coefficient ◽  
Second Step ◽  
Consecutive Reaction ◽  
Comparable Rate ◽  
Acidic Aqueous Solution

Studies of the rates and mechanisms of oxidation of four alkyl thiocyanates by peroxomonosulphate are reported, Analysis of the data is consistent with the occurrence of two consecutive reaction steps of comparable rate coefficient. The product of the second step appears to be the sulphonyl cyanide, RSO2CN.

scholarly journals Adsorption of Copper Ion in Acidic Aqueous Solution Using Rice Bran and Heat Treatment

2008 ◽  
Vol 31 (12) ◽  
pp. 749-754
Author(s):  
Kazuhiro HONDA ◽  
Takayuki YOSHIKAWA ◽  
Tuyoshi SASAKI ◽  
Tadashi SASAMOTO
Keyword(s):  
Heat Treatment ◽  
Aqueous Solution ◽  
Rice Bran ◽  
Copper Ion ◽  
Acidic Aqueous Solution

Kinetics, stoicheiometry, and mechanism in the bromination of aromatic heterocycles. I. Aqueous bromination of pyrazole, 1-methylpyrazole, and 3,5-dimethylpyrazole

1971 ◽  
Vol 24 (7) ◽  
pp. 1413 ◽  
Author(s):  
BE Boulton ◽  
BAW Coller
Keyword(s):  
Aqueous Solution ◽  
Potentiometric Titration ◽  
Electrode Potential ◽  
Rate Coefficients ◽  
Molecular Bromine ◽  
Aromatic Heterocycles ◽  
Dilute Aqueous Solution ◽  
Direct Attack ◽  
Rate Behaviour ◽  
Bromide Solutions

A procedure is described for monitoring the reactivity of a substrate towards bromine in aqueous bromide solutions, as a function of extent of reaction, by following the changes of electrode potential with time in the intervals between successive periods of electrolysis. ��� The title compounds show 1 : 1 stoicheiometry with substitution in the 4-position. The observed rate behaviour may be understood in terms of direct attack by molecular bromine on the neutral substrate molecules, rate coefficients for dilute aqueous solution at 25�C being: ����� k20(Br2+pyrazole) = 3.8x105 dm3 mol-1 s-1, kH/kD = 1.39;����� k20(Br2+1.methylpyrazole) = 8.0x105 dm3 mol-1 s-1;����� k20(Br2+3,5-dimethylpyrazole) = 1.4x109 dm3 mol-1 s-1, kH/kD = 1.08 Values of pKa(pyrazole-H+) = 2.58 and pKa(3,5-dimethylpyrazole-H+) = 4.11 were determined by potentiometric titration methods.

Oxidation of CrIIIto CrVIinitiated by OHand SO4-in acidic aqueous solution A pulse radiolysis study

1997 ◽  
Vol 93 (24) ◽  
pp. 4265-4268 ◽  
Author(s):  
George V. Buxton ◽  
Fathi Djouider ◽  
D. Alan Lynch ◽  
Treena N. Malone
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Acidic Aqueous Solution
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