Reaction of .alpha.-hydroxyalkyl radicals and their anions with oxidized dithiothreitol: a pulse radiolysis and product analysis study

1989 ◽  
Vol 93 (10) ◽  
pp. 4331-4334 ◽  
Author(s):  
M. Shahid Akhlaq ◽  
Cherla P. Murthy ◽  
Steen Steenken ◽  
Clemens Von Sonntag
Keyword(s):  
Pulse Radiolysis ◽  
Product Analysis ◽  
Analysis Study ◽  
Hydroxyalkyl Radicals

Hydroxylation of Chlorotoluenes and Cresols: A Pulse Radiolysis, Laser Flash Photolysis, and Product Analysis Study

1997 ◽  
Vol 101 (51) ◽  
pp. 9837-9845 ◽  
Author(s):  
S. C. Choure ◽  
M. M. M. Bamatraf ◽  
B. S. M. Rao ◽  
Ranjan Das ◽  
H. Mohan ◽  
...  
Keyword(s):  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Product Analysis ◽  
Analysis Study

Phenylalanine: Its ˙OH and SO4˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

1993 ◽  
Vol 48 (6) ◽  
pp. 761-770 ◽  
Author(s):  
Degui Wang ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Radical Cation ◽  
Pulse Radiolysis ◽  
Side Reactions ◽  
Intramolecular Electron Transfer ◽  
Oh Radical ◽  
Product Analysis ◽  
Water Elimination ◽  
Deprotonation Reaction ◽  
Type Radical ◽  
Radical Yield

Phenylamine has been oxidized by radiolytically generated hydroxyl and sulfate radicals, the ensuing intermediates and their reactions have been studied by pulse radiolysis and product analysis in the absence and presence of oxidants such as Fe(CN)63- and O2. Upon OH radical attack, hydroxycyclohexadienyl-type radicals are mainly formed while Η-abstraction reactions can be neglected. In the presence of Fe(CN)63- these radicals are for the most part oxidized to the corresponding tyrosines (80%), except for the ipso-OH-adduct radicals (≈ 20%). It is concluded that ˙OH-addition is almost random, but with a slight avoidance of the metaposition relative to the ortho-, para- and ipso-positions. Oxygen adds reversibly to the OH-adduct radicals (kf = 1.8 × 108 dm3 mol-1 s-1, kr = 5.4 × 104 s-1). In this case, tyrosine formation occurs by HO2˙-elimination. However, due to side reactions, tyrosine formation only reaches 52% of the OH radical yield. The tyrosine yield drops to 10% in the absence of an oxidant.Upon SO4˙⁻-attack, decarboxylation becomes a major process (33% of SO4˙⁻) alongside the production of tyrosines (43%). Here, with Fe(CN)63- as the oxidant the formation of p-Tyr (18.5%) and m-Tyr (16.5%) is preferred over o-Tyr formation (8.5%). It is believed that in analogy to other systems a radical cation is formed immediately upon SO4˙⁻-attack which either reacts with water under the formation of hydroxycyclohexadienyl-type (“OH-adduct”) radicals, or decarboxylates after intramolecular electron transfer. The radical cation can also arise indirectly through H+-catalysed water elimination from the ˙OH-adduct radicals. At pH 2 and a dose rate of 0.0046 Gy s-1 CO2 formation matches the OH radical yield when ˙OH is the attacking radical. Below pH 2, G(CO2) decreases with falling pH. This indicates the occurrence of another, unimolecular, pathway under these conditions competing effectively with decarboxylation. This appears to be a relatively slow deprotonation reaction of the carboxylprotonated phenylalanine radical cation which gives rise to the benzyl-type radical.

On the photolysis of phthalic acid dialkyl esters: a product analysis study

1993 ◽  
Vol 72 (2) ◽  
pp. 147-152 ◽  
Author(s):  
G. Hizal ◽  
Q.Q. Zhu ◽  
Ch.-H. Fischer ◽  
P.M. Fritz ◽  
W. Schnabel
Keyword(s):  
Phthalic Acid ◽  
Product Analysis ◽  
Analysis Study
Sign in / Sign up

Export Citation Format

Share Document