The 2-oxo-3,3,5,5-tetramethylcyclopentanecarboxylic acid keto–enol system in aqueous solution — Generation of the enol by flash photolytic Wolff rearrangement of 2-diazo-4,4,6,6-tetramethylcyclohexane-1,3-dione followed by hydration of the acylketene thus formed

2005 ◽  
Vol 83 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Y Chiang ◽  
A J Kresge ◽  
V A Nikolaev ◽  
I Onyido ◽  
X Zeng
Keyword(s):  
Aqueous Solution ◽  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Perchloric Acid ◽  
Flash Photolysis ◽  
Keto Form ◽  
Wolff Rearrangement ◽  
Buffer Solutions ◽  
Solution Generation ◽  
Oxocarboxylic Acids

Flash photolysis of 2-diazo-4,4,6,6-tetramethylcyclohexane-1,3-dione in aqueous solution produced 2-oxo-3,3,5,5-tetramethylcyclopentylideneketene, which underwent hydration to the enol of 2-oxo-3,3,5,5-tetramethylcyclo pentanecarboxylic acid; the enol then isomerized to the keto form of the acid. Rates of hydration of the ketene and rates of ketonization of the enol were measured in perchloric acid, sodium hydroxide, and buffer solutions, and rate profiles were constructed. Rates of enolization of 2-oxo-3,3,5,5-tetramethylcyclopentanecarboyxlic acid were also measured, using bromine to scavenge the enol as it formed, and rates of enolization and ketonization were then combined to give the keto–enol equilibrium constant pKE = 1.65. This and other results are discussed in comparison with the behavior of the unmethylated 2-oxocyclopentanecarboxylic acid system.Key words: flash photolysis, photo-Wolff reaction, ketene hydration, enolization, ketonization, keto–enol equilibria, β-oxocarboxylic acids.

Ketonization of the unusually acidic elongated enol generated by flash photolytic decarboxylation of p-formylphenylacetic acid in aqueous solution

2008 ◽  
Vol 86 (2) ◽  
pp. 101-104 ◽  
Author(s):  
Yvonne Chiang ◽  
Kirill Kolmakov ◽  
A Jerry Kresge
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Perchloric Acid ◽  
Flash Photolysis ◽  
Isotope Effects ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

Rates of photolysis of p-formylphenylacetic acid were measured flash photoytically in perchloric acid and sodium hydroxide solutions, and also in acetic acid, biphosphate ion, and tris-(hydroxymethyl)methaneammonium ion buffers, using H2O and D2O as solvents. The results provide rate profiles and solvent isotope effects, which indicate that photolysis occurs through an elongated enol intermediate. This enol is unusually strongly acidic, by some two to three pQa units, when compared with simple non-elongated enols.Key words: flash photolysis, elongated enols, rate profiles, solvent isotope effects.

Generation of 6-methylene-2,4-cyclohexadienylidene ketene by flash photolysis of benzocyclobutenone in aqueous solution and study of the reactions of this ketene in that medium

2003 ◽  
Vol 81 (6) ◽  
pp. 607-611 ◽  
Author(s):  
Y Chiang ◽  
A J Kresge ◽  
H -Q Zhan
Keyword(s):  
Aqueous Solution ◽  
Ring Opening ◽  
Flash Photolysis ◽  
Isotope Effects ◽  
Buffer Solutions ◽  
Product Identification ◽  
Rate Profile ◽  
Solvent Isotope ◽  
Rates Of Decay ◽  
Solvent Isotope Effects

Flash photolysis of benzocyclobutenone in aqueous solution produced a transient species with a microsecond lifetime whose rates of decay were measured in perchloric acid, sodium hydroxide, and buffer solutions over the acidity range [H+] 1 × 10–13 – 100 M. This produced a rate profile, isotope effects, and buffer behaviour typical of ketene reactions, and that, together with product identification, served to identify this transient as 6-methylene-2,4-cyclohexadienylidene ketene, formed by electrocyclic opening of the four-membered ring of benzocyclobutenone. Comparison of rates of reaction of this ketene with those of its saturated analog, pentamethyleneketene, produced some expected as well as some unexpected results. Key words: cyclobutenone chemistry, electrocyclic ring opening, ketene hydration, rate profile, solvent isotope effects.

Flash photolysis of phenylacetatopentaminecobalt(III) in aqueous solution. Generation of benzyl radicals and their reversible trapping by cupric ions in homogeneous and micellar solutions

1984 ◽  
Vol 62 (11) ◽  
pp. 2355-2358 ◽  
Author(s):  
J. C. Scaiano ◽  
W. J. Leigh ◽  
G. Ferraudi
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Micellar Solutions ◽  
Aqueous Systems ◽  
Solution Generation ◽  
Benzyl Radicals ◽  
Anionic Micelles ◽  
Decay Path

The photodecomposition of [Co(NH3)5OC(O)CH2C6H5](ClO4)2 is a convenient source of benzyl radicals in aqueous systems. The radicals react with cupric ions with a rate constant of (2.1 ± 0.2) × 107 M−1 s−1 to yield a complex that is formed reversibly. This complex can decay to Cu(I), but at high radical concentrations the recombination of benzyl radicals in equilibrium with it can become the predominant decay path. The reaction of benzyl radicals (from 1,3-diphenylacetone) in anionic micelles in the presence of Cu2+ leads to strong signals from the same intermediate, CuCH2C6H52+.

Modification of activated carbon using sodium acetate and its regeneration using sodium hydroxide for the adsorption of copper from aqueous solution

Carbon ◽  
2007 ◽  
Vol 45 (5) ◽  
pp. 1081-1084 ◽  
Author(s):  
Dan Mugisidi ◽  
Aria Ranaldo ◽  
Johny W. Soedarsono ◽  
Muhammad Hikam
Keyword(s):  
Aqueous Solution ◽  
Activated Carbon ◽  
Sodium Hydroxide ◽  
Sodium Acetate

Flash photolysis and pulse radiolysis of the Co(sep)3+-X- (sep = sepulchrate; X = I, Br) systems in aqueous solution

1986 ◽  
Vol 25 (23) ◽  
pp. 4249-4252 ◽  
Author(s):  
Fernando Pina ◽  
Mauro Maestri ◽  
Roberto Ballardini ◽  
Quinto G. Mulazzani ◽  
Mila D'Angelantonio ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Flash Photolysis

Studies on Grafting Copolymerization of Lactic Acid onto Cornstarch Catalyzed with Sodium Hydroxide

2011 ◽  
Vol 233-235 ◽  
pp. 1906-1910
Author(s):  
Ying Mo Hu ◽  
Qing Ling Wang ◽  
Jian Hua Zhu ◽  
Yang Liu ◽  
Xue Yang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Lactic Acid ◽  
Sodium Hydroxide ◽  
Convenient Method ◽  
Graft Copolymerization ◽  
Good Adhesion ◽  
Acid Copolymer ◽  
Grafting Copolymerization ◽  
Grafting Degree

A convenient method to synthesize starch/lactic acid copolymer was studied in this work. Copolymer of starch graft with lactic acid (LA) was directly prepared by reaction of cornstarch with lactic acid in sodium hydroxide (NaOH) aqueous solution as a catalyst. The product was characterized by IR and WAXD, and the good adhesion between the two components has been observed by SEM. The results showed that the highest grafting degree could reach 33.60% when the graft copolymerization was carried in 0.40 mol·L-1 NaOH aqueous for 9 h at 90°C with the 1: 5~6 ratio of starch and lactic acid.

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