Polyethylene Glycols as Efficient Catalysts for the Oxidation of Xanthine Alkaloids by Ceric Ammonium Nitrate in Acetonitrile: A Kinetic and Mechanistic Approach

Table 5

Activation parameters of theophylline in different PEG media.

Type of PEG	PEG % (V/V)	𝑘^′′ at 300 K	Equation	𝑅^2	Δ𝐻^#	Δ𝐺^#	−Δ𝑆^# J/Kmol
					kJ/mol
PEG-200	0.5	0.39	𝑦=−1.426𝑥−1.899	0.993	11.8	66.1	181
	1.0	0.49	𝑦=−2.6456𝑥+2.392	0.993	21.9	75.0	177
	2.0	0.51	𝑦=−2.8259𝑥+3.021	0.984	23.4	75.0	172
	3.0	0.53	𝑦=−3.3595𝑥+4.821	0.964	27.8	74.9	157
	4.0	0.56	𝑦=−3.5908𝑥+5.700	0.995	29.8	74.8	150
	5.0	0.65	𝑦=−3.8286𝑥+6.599	0.984	31.7	74.3	142
PEG-300	0.5	0.23	𝑦=−5.1973𝑥+10.21	0.952	43.1	76.7	112
	1.0	0.30	𝑦=−4.348𝑥+7.607	0.992	36.0	76.2	134
	2.0	0.37	𝑦=−3.7544𝑥+5.847	0.979	31.1	75.5	148
	3.0	0.39	𝑦=−3.6694𝑥+5.622	0.970	30.4	75.4	150
	4.0	0.44	𝑦=−3.2984𝑥+4.504	0.969	27.3	75.3	160
	5.0	0.51	𝑦=−3.0744𝑥+3.877	0.998	25.5	75.0	165
PEG-400	0.5	0.16	𝑦=−5.2588𝑥+9.971	0.995	43.6	77.8	114
	1.0	0.25	𝑦=−3.8986𝑥+5.902	0.999	32.3	76.7	148
	2.0	0.28	𝑦=−4.1044𝑥+6.732	0.986	34.0	76.3	141
	3.0	0.30	𝑦=−4.2289𝑥+7.215	0.988	35.1	76.2	137
	4.0	0.32	𝑦=−4.4535𝑥+8.039	0.978	36.9	75.9	130
	5.0	0.44	𝑦=−3.187𝑥+4.113	0.993	26.4	75.3	163
PEG-600	0.5	0.11	𝑦=−4.8443𝑥+8.296	0.956	40.2	78.6	128
	1.0	0.21	𝑦=−3.2573𝑥+3.634	0.953	27.0	77.1	167
	2.0	0.25	𝑦=−3.1274𝑥+3.359	0.981	25.9	76.6	169
	3.0	0.35	𝑦=−2.1206𝑥+0.333	0.979	17.6	75.8	194
	4.0	0.44	𝑦=−1.5663𝑥−1.290	0.980	13.0	68.8	186
	5.0	0.60	𝑦=−0.7623𝑥−3.664	0.958	6.33	56.4	167