Sigma value

Taft sigma values cr perform a similar function with respect to aliphatic and alicyclic systems. Values of cr are listed in Table 9.1. 

These sigma values are for unrestricted flow over relatively flat, uniform terrain. They may require modification for application to rough terrain or restricted flow conditions (e.g., within the confines of a narrow valley, coastal or desert areas - see IAEA, 1980). 

The effeetive area of the eentrifuge, known as the Sigma value, S, is obtained by integration of equation 4.18, as follows. 

Note, since different types of machine have different sigma values, always take care in checking the precise definition of S. 

Values of a0-, ar and [Pg.497]

III. SUBSTITUENT EFFECTS IN AROMATIC SYSTEMS A. Sigma Values from Reactivity Studies... 

Most of the information available concerns SOMe and S02Me. Bordwell and his colleagues were the leading pioneers in determining sigma values for these groups. The results of the main determinations of the ordinary Hammett o constant and of the exalted constant o are shown in Tables 3 and 4 respectively. 

TABLE 3. Sigma values for SO Me and S02Me based on the ionization of benzoic acids and related processes... 

TABLE 7. Sigma values for fluoroalkylsulflnyl and fluoroalkylsulfonyl groups... 

TABLE 11. Sigma values from measurements in the gas-phase and in aqueous solution130... 

V-Alkylisothioazolidines, synthesis of 733 Alkylsulphinylcycloalkanes, synthesis of 252 Alkylsulphinyl groups, sigma values of 498-505... 

Fluorenyl carbanions 1055, 1065, 1066 Fluoroalkylsulphinyl groups, sigma values of 507-509... 

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