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Table 5.3 Electronic substituent constants.

Group

Hammett

Inductive

Taft

Swain-Lupton

constantsa

constants'5

constantsc

constants'1

Om

°p

01

O*

F

R

-H

0.00

0.00

0.00

0.49

0.00

0.00

-CH3

-0.07

-0.17

-0.05

0.00

-0.04

-0.13

-C2H5

-0.07

-0.15

-0.05

-0.10

-0.05

-0.10

-Cl

0.37

0.23

0.47

0.41

-0.15

-Br

0.39

0.27

0.45

0.44

-0.17

-I

0.35

0.30

0.39

0.40

-0.19

-NO2

0.71

0.78

0.67

0.16

-OH

0.12

-0.37

0.25

0.29

-0.64

OCH3

0.12

-0.27

0.25

0.26

-0.51

-C6H5

0.06

-0.01

0.10

0.60

0.08

-0.08

aHammett, L.P. (1940) Physical Organic Chemistry, p. 186. New York: McGraw Hill.

bCharton, M. (1964) Definition of 'inductive' substituent constants. Journal ofOrganic Chemistry 29, 1222-1227. cTaft, R.W. (1956) Separation of polar, steric and resonance effects. Steric Effects in Organic Chemistry, edited by M.S.Newman, pp. 559675. New York: John Wiley.

dHansch, C. and Leo, A. (1979) Substituent Constants for Correlation Analysis in Chemistry and Biology. New York: John Wiley. More comprehensive lists of electronic substituent constants can be found in Hansen and Leo (above) and Tute, M.S. (1971) Principles and practice of Hansch analysis: A guide to structure-activity correlation for the medicinal chemist. In Advances in Drug Research, edited by N.J.Harper and A.B.Simmonds, Vol. 6, pp. 1-77. London: Academic Press.

Fukata and Metcalf's results can be expressed in the form of Equation [5.8], which is the equation for the best straight line through the points in Figure 5.2.

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