The standard enthapies of combustion Delta(c)H((liq.))degrees of the branched esters 1,2 and ethers 3 were measured calorimetrically. The enthalpies of vaporisation Delta(v)H degrees of 1-3 were obtained from the temperature function of the vapor pressure in a flow system. The following results are obtained from these data : Delta(f)H((liq.))degrees Delta(v)H degrees for 1a : -556.1+/-1.6, 44.39+/-0.16; 1b : -587.4+/-1.6, 44.49+/-0.39; 1c : -609.5+/-1.2, 50.57+/-0.51; 1d : -614.7+/-1.5, 48.39+/-0.18; 1e : -616.4+/-1.0, 50.39+/-0.34; 2a : -, 51.73+/-0.23; 2b : -605.7+/-2.7, 60.04+/-0.63; 2c : -554.5+/-1.3, -; 2d : -581.8+/-1.5, 42.81+/-0.34; 2e : -624.78+/-0.98, 50.84+/-0.57; 3a : -409.1+/-2.0, 40.94+/-0.30; 3b : -428.34+/-0.90, 46.14+/-0.25; 3c : -406.7+/-1.5, 44.90+/-0.50; 3d : -, 53.13+/-0.19 kJ mol(-1). From Delta(f)H((gas))degrees of 1-3 and a critical choice from known data were derived new values of group increments for the estimation of standard enthalpies of formation of esters CO2 [2C] -327.05, CH3[CO2]-42.05, CH2[CO2, C]-17.40, CH[CO2, 2C] -7.40, C[CO2, 3C] 4.51, CH30 [O] -42.05, CH20[O, C] -33.76, CH0[O, 2C] - 31.30, C-0[O, 3C] -20.20 and of ethers O[2C] -99.23, CH3[O] -42.05, CH2[O, C] -33.06, CH[O, 2C] - 25.64, C[O, 3C] -18.16, Ph[O] 72.02 kJ mol(-1).