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, and 1.9 Â 10 À4 -4.0 Â 10 À2 M for electrodes composed with the ionophores I -V, respectively. All electrodes showed pH range of about 4.0 to 11.5 and working temperature range of 22 to 70 8C with isothermal temperature coefficients of 1.19 Â 10 À3 , 1.16 Â 10 À3 , 1.16 Â 10 À3 , 1.00 Â 10 À3 , and 1.32 Â 10 À3 V/8C for electrodes I -V respectively.

Rates and products of reaction and Arrhenius activation parameters were determined for the gas-phase thermolysis of 14 substrates of the title compounds using sealed pyrex reactor tubes and HPLC/UV-VIS to monitor substrate pyrolysis. The 14 compounds under study -( p-methylphenyl)-3-oxo-(3), and N-( p-methoxyphenyl)-3-oxobutanamide (4), in addition to (i) four substrates (5-8) obtained by the replacement of the pairs of methylene hydrogens at the 2-position of compounds (1-4), each pair by a phenylhydrazono group; (ii) three arylhydrazono derivatives (9-11) in which Cl, CH 3 , or OCH 3 groups are substituted at the para position of the phenylhydrazono moiety of compound 5; (iii) 3-oxobutanamide (acetoacetamide, 12), N-phenyl-3-oxo-3-phenylpropanamide (13), and N,N -diphenylpropanediamide (14). The reactions were conducted over 374-546 K temperature range, and the values of the Arrhenius log A(s −1 ) and E a (kJ mol −1 ) of these reactions were, respectively, 12.0 ± 2.0 and 119.2 ± 17.0 for the ketoanilides (1-4, 12-14), andCorrespondence to: Nouria A. Al-Awadi;

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