-75 -50 -25 0 25 50 75 100 125 150 175 200

9

12

15

18

21

24

27

30

33

36

39

en

erg

y b

arr

ier

(kca

l/m

ol)

temperature (C)

five half lives:

1 s

1 h

24 h

200 250 300 350 400

1

2

4

8

16

32

64

sp

ee

du

p

temperature (C)

barrier

(kcal/mol)

10

15

20

25

30

35

35 kcal/mol

10 kcal/mol

low ksolvhigher E

high ksolvlower E

normal region:less reactive,

more selective

negative slope:

more reactive,

more selective!

vertical slope:

constant selectivity