Correlation of vaporisation enthalpies, Δ^g_lH^o_m(298.15 K), of 1,3- and 1,4-di-methoxy-substituted benzenes with their Kovats's indices (J_x)^a.

Compound	J x b	ΔglHom(298.15 K)exp, kJ mol−1	ΔglHom(298.15 K)calcc, kJ mol−1	Δ d, kJ mol−1
1,3-Dimethoxy-benzene	1143	59.7 ± 0.2 (ref. 5)	60.6	−0.9
1,4-Dimethoxy-benzene	1158	61.6 ± 0.2 (ref. 5)	61.1	0.5
3,5-Dimethoxy-toluene	1233	64.5 ± 1.2 (ref. 30)	63.5	1.0
1,3,5-Tri-methoxy-benzene	1405	68.7 ± 0.4e	69.0	−0.3
2,4,6-Tri-methoxy-toluene	1486	—	71.6	—

^aUncertainties are given as the standard uncertainty (0.683 level of confidence, k = 1).

^bKovats's indices, J_x, on standard non-polar columns from ref. 29.

^cCalculated using eqn (5).

^dDifference between experimental and calculated by eqn (5) values (columns 3 and 4).

^eExperimental data measured by using the transpiration method from (see Table 1).