Chemistry Reference
In-Depth Information
Table 10. 23.
Rate of reaction (unit: dm
3
mol
−1
s
−1
) of
α
-hydroxyalkyl radicals with purines.
(Aravindakumar et al. 1994)
•
C(CH
3
)
2
OH
•
CH(CH
3
)OH
•
CH
2
OH
Substrate
pH
HypH
+
0.4
7. 8
×
10
7
2.2
×
10
7
∼
5
×
10
6
∼
4
×
10
6
Hyp
6.5
n.d.
n.d.
InoH
+
3.2
×
10
7
3.0
×
10
7
∼
6
×
10
6
0.4
6.4
×
10
6
∼
5
×
10
6
Ino
6.5
n.d.
∼
10
6
Ino anion
11.2
n.d.
n.d.
AdoH
2
2+
/AdeH
+
1.2
×
10
8
4.3
×
10
7
4.4
×
10
6
0.4
AdoH
+
4.7
×
10
7a
1.5
×
10
7
∼
3
×
10
6
0.4
< 10
6a
Ado
7
n.d.
n.d.
< 10
6a
Ado anion
13.6
n.d.
n.d.
dAdoH
+
1. 3
×
10
8
3.1
×
10
7
5.5
×
10
6
0.4
GuoH
+
4.3
×
10
7
1.8
×
10
7
5.7
×
10
6
0.4
1MeGuoH
+
8.0
×
10
7a
0.5
n.d.
n.d.
dGuoH
+
0.4
7.1
×
10
7
1.4
×
10
7
∼
4
×
10
6
n.d., Not determined
a
From Moorthy and Hayon (1975)
reactivity of
•
CH
2
OH is so low, that its reaction is barely noticed, even at low
steady-state concentrations of these radicals (Table 10.23). The product which is
typically observed is the
C
(8)-alkylated purine, [e.g., reactions (217) and (218)].
As can be seen from Table 10.24, the consumption of the purines is noticeably
higher than is accounted for by the
C
(8)-alkylated product. Thus, other, as yet
not established, reactions must take place as well. It is recalled that the
C
(8) posi-
tion rates among the sites preferred by electrophilic radicals and thus is possibly
not the most preferred one for an attack by the nucleophilic alkyl radicals. Yet
the EPR spectra of the intermediates formed in the reactions of the H
2
NCOCH
2
•
radical with Ade and Gua derivatives have also been interpreted as being mainly
due to the
C
(8)-adduct radicals (Wang et al. 1997). Methyl radicals, generated in
Search WWH ::
Custom Search