Page 1013 - Advanced Organic Chemistry Part A - Structure and Mechanisms, 5th ed (2007) - Carey _ Sundberg

of absolute rates and E are given in Table 11.3. The examples include hydrogen 997
a
abstraction (Section A), addition (Section B), ring closure and opening (Section C),
and other types of reactions such as fragmentation and halogen atom abstraction SECTION 11.2
(Section D). In the sections that follow, we discuss some of the reactivity relationships Characteristics of
Reactions Involving
revealed by these data. Radical Intermediates

Table 11.3. Absolute Rates for Some Free Radical Reactions a

Reaction Rate/E a Reference
A. Hydrogen abstraction reactions
.
6
–1 –1
1 Ph + Ph H + . 4.8 x 10 M s b
O O
) CO
5
2 (CH 3 3 . + (CH ) CPh (CH ) COH + (CH ) CPh 8.7 x 10 M s c
3 2 .
–1 –1
3 2
3 3
H
) CO
3 (CH 3 3 . + (CH ) COH + . 8.3 x 10 M s c
6
–1 –1
3 3
O O
4 Cl . + 9
–1 –1
(free) H Cl + . 4.7 x 10 M s d
.
5 Cl + HCl + . 7 –1 –1 d
(benzene 4.3 x 10 M s
complex)
7
–1 –1
6 CH 3 . + Bu SnH CH + Bu Sn . 1.0 x 10 M s e
4
3
3
E = 3.2 kcal/mol
a
7
–1 –1
7 (CH ) 3 C . + Bu SnH (CH ) CH + Bu Sn . 1.8 x 10 M s e
3
3 3
3
3
E = 2.95 kcal/mol
a
.
8
8 Ph + Bu SnH C H + Bu Sn . 7.8 x 10 M s f
–1 –1
6 6
3
3
9
9 CF CF CF 2 . + Bu SnH CF CF CF H + Bu Sn . 2.0 x 10 M s g
–1 –1
3
2
3
2
3
2
3
10 PhCH 2 . PhCH 3 + PhS . 3.1 x 10 M s h
5
–1 –1
+ PhSH
6
–1 –1
11 RCH 2 . + (CH 3 ) 3 CSH RCH 3 + (CH 3 ) 3 CS . 8 x 10 M s i
12 CH 2 . + PhSeH CH + PhSe . 2.1 x 10 M –1 s –1 j
9
3
5
13 (CH ) CC O + Bu 3 SnH (CH ) 3 CCH O + Bu Sn . 3.0 x 10 M s k
–1 –1
3 3
3
.
3
6
–1 –1
14 RC . O + Bu SnH RCH O + Bu Sn . 1.3 x 10 M s l
3
3
8
15 Ph C CPh + Bu 3 SnH Ph C CHPh + Bu Sn . 7.5 x 10 M s m
–1 –1
2
3
.
2
16 RCH 2 . + [(CH ) Si] SiH RCH 3 + [(CH ) Si] Si . 1.0 x 10 M s n
5
–1 –1
3
3
3 3
3 3
. 9 –1 –1 m
) Si] SiH
17 Ph C CPh + [(CH 3 3 3 Ph2C CHPh + [(CH ) Si] Si 1.6 x 10 M s
3
3 3
2
.
5
–1 –1
18 RC . O + [(CH ) Si] SiH RCH O + [(CH ) Si] Si . 1.0 x 10 M s l
3 3
3
3
3 3
(Continued)