“…According to a reported study, the aminyl radical will form formaldehyde via a five-membered transition state (R9). The route is base-catalyzed and O 2 -independent . The alkoxyl radical can undergo a 1,2 hydrogen shift and be converted to a hydroxyalkyl radical. , Formaldehyde can be produced directly from the alkoxyl radical via an O 2 -independent β-scission reaction (R10).…”
Section: Results
and Discussionmentioning
confidence: 99%
“…Additionally, hydroxyl radicals can abstract hydrogen atoms from the amino group forming aminyl radical. According to a reported study, the aminyl radical will form formaldehyde via a five-membered transition state (R9). The route is base-catalyzed and O 2 -independent .…”
Interfacial reactions between H 2 O 2 and metal oxides are important in several fields but are yet not fully understood. Recently, tris(hydroxymethyl)aminomethane (Tris) was used as a probe in detecting the intermediate hydroxyl radical (HO • ) during such process via the formation of formaldehyde (CH 2 O). In this work, we evaluate two probes (methanol and Tris) for detection of surface bound HO • by investigating the O 2 and pH effects on the production of formaldehyde. Moreover, we also examine the pH effect on the production of formaldehyde from Tris in the catalytic decomposition of H 2 O 2 on ZrO 2 . The influence of O 2 and pH on the yield of formaldehyde under homogeneous conditions was studied via γradiolysis of water. The solution was either deoxygenated or saturated with gas containing 20% O 2 , and the pH was ranging from 7.0 to 9.0. In the γ-radiolysis experiment, O 2 shows a strong impact on the yield of formaldehyde: 14−68% for methanol and 16−29% for Tris. However, during the catalytic decomposition of H 2 O 2 , O 2 only enables a 30% enhancement of the production of CH 2 O when using Tris as the scavenger. While for methanol, the O 2 effect is almost negligible, and the production of CH 2 O from Tris is much higher than that from methanol. For practical reasons, only Tris was studied when evaluating the pH effect. A significant increase in the production of formaldehyde is observed by increasing pH during γ-radiolysis of water while an even more pronounced pH-dependent increase is observed in the catalytic decomposition of H 2 O 2 on ZrO 2 . The former indicates that the scavenging yield is base-catalyzed while the latter indicates that the formation of HO • is also base-catalyzed. On the basis of the observed effects of O 2 and pH, we propose a mechanism for the production of formaldehyde from Tris. The mechanism accounts for the observed impacts of O 2 and pH on the yield of formaldehyde.(R2)
“…According to a reported study, the aminyl radical will form formaldehyde via a five-membered transition state (R9). The route is base-catalyzed and O 2 -independent . The alkoxyl radical can undergo a 1,2 hydrogen shift and be converted to a hydroxyalkyl radical. , Formaldehyde can be produced directly from the alkoxyl radical via an O 2 -independent β-scission reaction (R10).…”
Section: Results
and Discussionmentioning
confidence: 99%
“…Additionally, hydroxyl radicals can abstract hydrogen atoms from the amino group forming aminyl radical. According to a reported study, the aminyl radical will form formaldehyde via a five-membered transition state (R9). The route is base-catalyzed and O 2 -independent .…”
Interfacial reactions between H 2 O 2 and metal oxides are important in several fields but are yet not fully understood. Recently, tris(hydroxymethyl)aminomethane (Tris) was used as a probe in detecting the intermediate hydroxyl radical (HO • ) during such process via the formation of formaldehyde (CH 2 O). In this work, we evaluate two probes (methanol and Tris) for detection of surface bound HO • by investigating the O 2 and pH effects on the production of formaldehyde. Moreover, we also examine the pH effect on the production of formaldehyde from Tris in the catalytic decomposition of H 2 O 2 on ZrO 2 . The influence of O 2 and pH on the yield of formaldehyde under homogeneous conditions was studied via γradiolysis of water. The solution was either deoxygenated or saturated with gas containing 20% O 2 , and the pH was ranging from 7.0 to 9.0. In the γ-radiolysis experiment, O 2 shows a strong impact on the yield of formaldehyde: 14−68% for methanol and 16−29% for Tris. However, during the catalytic decomposition of H 2 O 2 , O 2 only enables a 30% enhancement of the production of CH 2 O when using Tris as the scavenger. While for methanol, the O 2 effect is almost negligible, and the production of CH 2 O from Tris is much higher than that from methanol. For practical reasons, only Tris was studied when evaluating the pH effect. A significant increase in the production of formaldehyde is observed by increasing pH during γ-radiolysis of water while an even more pronounced pH-dependent increase is observed in the catalytic decomposition of H 2 O 2 on ZrO 2 . The former indicates that the scavenging yield is base-catalyzed while the latter indicates that the formation of HO • is also base-catalyzed. On the basis of the observed effects of O 2 and pH, we propose a mechanism for the production of formaldehyde from Tris. The mechanism accounts for the observed impacts of O 2 and pH on the yield of formaldehyde.(R2)
“…At the same time, oxygen only just slightly affected the yields of the C-C destruction products. 27 The nitrogen-centered radicals formed from starting substrates do not interact with oxygen because they are oxidizers themselves.…”
Section: Discussionmentioning
confidence: 99%
“…The possibility of radiation-induced destruction involving C–C bond cleavage in amine-containing organic compounds has been shown in our earlier studies that were performed on a series of 1,2-amino alcohols. 27 The mechanism of amino alcohol destruction on radiolysis of their aqueous solutions includes the stages of formation and subsequent fragmentation of nitrogen-centered radicals according to the scheme below: …”
Section: Discussionmentioning
confidence: 99%
“…To enable decomposition via cleavage of two bonds in β-position with respect to the radical-center formation of a five-membered transition state (I) has been proposed. 27 The reaction (1) is strongly favored by the hydrogen bond –N···H–O– between vicinal hydroxyl and amino groups of α-amino alcohols. It should be noted that cysteine addition suppressed the C–C destruction of amino alcohols, which may be accounted for by the reduction of aminyl radicals by S–H groups of cysteine molecules.…”
The action of hypochlorous acid (HOCl) and γ-radiation on aqueous lysosphingolipid dispersions was found to produce 2-hexadecenal (Hex). This process includes the stages of formation of nitrogen-centered radicals from the starting molecules and the subsequent fragmentation of these radicals via the rupture of C–C and O–H bonds. These findings prove the existence of a nonenzymatic pathway of sphingolipid destruction leading to the formation of Hex, which possesses a wide spectrum of biological activity. Analysis of the effect of HOCl on transplantable rat glioma C6 cells and human embryonic kidney 293 cells points to the formation of Hex. This suggests that the described mechanism of free-radical destruction of sphingolipids may be replicated on cell culture under the stress of active chlorine forms.
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