EXPERIMENTAL ENTHALPIES OF FORMATION AND STRAIN OF THE METHYLATED 1-AMINO-2-PHENYLETHANES

The standard molar enthalpies of formation Delta H-f degrees(liq) at t he temperature t = 298.15 K were determined using combustion calorimet ry for N-methyl-3-methyl-3-phenyl-2-butaneamine 1a, N,N-dimethyl-3-met hyl-3-phenyl-2-butaneamine 1b, N-methyl-2,3-dimethyl-3-phenyl-2-butane amine 2a, and N,N-dimethyl-2,3-dimethyl-3-phenyl-2-butaneamine 2b. The standard molar enthalpies of vaporization Delta H(vap)degrees of thes e compounds were obtained from the temperature variation of the vapor pressure measured in a flow system. The following standard molar entha lpies of formation in gaseous phase Delta H-f degrees(g) are obtained from these data: for 1a -10.9 +/- 1.9; 1b -3.6 +/- 1.8; 1c -26.6 +/- 1 .4, and 1d -23.0 +/- 1.8 kJ mol(-1). From the standard molar enthalpie s of formation for gaseous compounds which are available in the litera ture, improved values for the increments of the Benson group addivitiy scheme of amines were calculated. They are used to determine the stra in enthalpies of the amines 1 and 2 from this investigation.