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

Table 6

Activation parameters of theobromine 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	0.21	𝑦 = −5.2713𝑥+10.31	0.999	43.7	80.0	111
	1.0	0.23	𝑦 = −5.9167𝑥+12.54	0.999	49.1	77.0	93.3
	2.0	0.30	𝑦 = −4.7454𝑥+8.893	0.996	39.3	76.2	123
	3.0	0.32	𝑦 = −4.6086𝑥+8.510	0.999	38.2	76.0	126
	4.0	0.35	𝑦 = −4.4002𝑥+7.950	0.979	36.5	75.8	131
	5.0	0.44	𝑦 = −3.5467𝑥+5.326	0.981	29.4	75.3	153
PEG-300	0.5	0.16	𝑦 = −5.8962𝑥+12.17	0.973	48.9	77.7	96.3
	1.0	0.21	𝑦 = −4.983𝑥+9.385	0.980	41.3	77.0	119
	2.0	0.23	𝑦 = −5.2059𝑥+10.27	0.987	43.0	76.6	112
	3.0	0.30	𝑦 = −5.236𝑥+10.41	0.972	43.4	76.7	111
	4.0	0.35	𝑦 = −4.632𝑥+8.798	0.956	38.4	75.6	124
	5.0	0.42	𝑦 = −4.6308𝑥+8.917	0.962	38.4	75.3	123
PEG-400	0.5	0.14	𝑦 = −6.9315𝑥+15.48	0.987	57.5	78.1	68.8
	1.0	0.21	𝑦 = −6.0803𝑥+13.08	0.953	50.4	77.0	88.8
	2.0	0.30	𝑦 = −4.5372𝑥+8.261	0.971	37.6	76.0	128
	3.0	0.35	𝑦 = −5.2988𝑥+10.96	0.972	43.9	75.7	106
	4.0	0.35	𝑦 = −6.2994𝑥+14.29	0.978	52.3	108	186
	5.0	0.42	𝑦 = −5.7161𝑥+12.49	0.997	47.4	76.1	93.7
PEG-600	0.5	0.18	𝑦 = −3.4127𝑥+3.971	0.995	28.3	77.5	164
	1.0	0.21	𝑦 = −3.0241𝑥+2.815	1.00	25.0	77.2	174
	2.0	0.28	𝑦 = −2.0791𝑥−0.0386	0.996	17.2	76.3	197
	3.0	0.32	𝑦 = −2.3784𝑥+1.079	0.998	19.7	79.4	188
	4.0	0.42	𝑦 = −1.7943𝑥−0.569	0.963	14.8	72.4	192
	5.0	0.51	𝑦 = −2.9311𝑥+3.403	0.995	24.3	75.0	169