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

Table 3

Activation parameters of Xanthine 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	0.09	𝑦=−6.7533𝑥+14.44	0.987	56.0	79.2	77.5
	1.0	0.11	𝑦=−7.6965𝑥+17.79	0.989	63.9	78.7	49.6
	2.0	0.14	𝑦=−7.2183𝑥+16.39	0.999	60.0	78.3	61.3
	3.0	0.16	𝑦=−7.2597𝑥+16.71	0.986	60.2	77.7	58.6
	4.0	0.18	𝑦=−7.225𝑥+16.72	0.977	59.9	77.4	58.5
	5.0	0.21	𝑦=−6.8661𝑥+15.69	0.971	57.0	77.1	67.1
PEG-300	0.5	0.07	𝑦=−6.3772𝑥+12.96	0.961	52.9	79.8	89.8
	1.0	0.09	𝑦=−6.2301𝑥+12.70	0.983	51.7	79.0	91.9
	2.0	0.11	𝑦=−7.0542𝑥+15.55	0.987	58.8	79.2	68.2
	3.0	0.14	𝑦=−6.7082𝑥+14.77	0.951	55.7	78.1	74.7
	4.0	0.14	𝑦=−6.7034𝑥+14.74	0.966	55.6	78.1	75.0
	5.0	0.16	𝑦=−6.4505𝑥+14.04	0.958	53.5	77.7	80.8
PEG-400	0.5	0.11	𝑦=−2.0567𝑥−1.059	0.999	17.0	73.4	188
	1.0	0.14	𝑦=−1.6434𝑥−2.177	0.980	13.6	67.3	179
	2.0	0.14	𝑦=−4.9725𝑥+8.909	0.999	41.2	78.1	123
	3.0	0.21	𝑦=−4.4045𝑥+7.418	0.999	36.5	77.0	135
	4.0	0.28	𝑦=−3.7414𝑥+5.514	0.991	31.0	76.3	151
	5.0	0.30	𝑦=−3.5601𝑥+4.983	0.985	29.5	76.3	156
PEG-600	0.5	0.16	𝑦=−3.4399𝑥+3.886	0.957	28.5	78.0	165
	1.0	0.18	𝑦=−3.4127𝑥+3.971	0.995	28.3	77.5	164
	2.0	0.18	𝑦=−4.5044𝑥+7.594	1.00	37.3	77.5	134
	3.0	0.21	𝑦=−4.1343𝑥+6.498	0.994	34.3	77.2	143
	4.0	0.30	𝑦=−2.6889𝑥+2.060	0.999	22.3	76.3	180
	5.0	0.39	𝑦=−2.2924𝑥+0.992	0.999	19.0	75.7	189