MEASUREMENTS OF ENTHALPIES OF FORMATION O F 2,3-DICHLOROBUTANE IN GASEOUS STATE

Two samples of pure mezo- and d, l-2, 3-dichlorobutanes were obtained from their mixture by fractional distillation, and their enthalpies of vaporization at 25 degrees C were measured by using an LKB-8721-3 vap orization calorimeter, they are 38.41 +/- 0.07 (mezo-) and 39.73 +/- 0 .05 (d, l-) kJ/mol, respectively. A mixture sample with (mezo-/d, l-)= 1.34/1 was used combustion experiments, its enthalpies of combustion a t 25 degrees C were determined by using a rotating bomb combustion cal orimeter with a tantanum lined bomb, as -2519.74 +/- 1.06 kJ/mol. By u sing the literature's enthalpies of isomerizm between the liquid mezo- and d, l-2, 3-dichlorobutanes, -1.13 +/- 0.21 kJ/mol, measured by the equilibrium method, enthalpies of combustion of mezo- and d, l-2, 3-d ichlorobutanes were obtained. Then enthalpies of formation of both in gaseous state were derived as, -202.34 +/- 1.72 (mezo-) and -202.15 +/ - 1.72 (d, l-) kJ/mol, respectively. According to the following equati on: a,b-C4H8Cl2(g)+n-C4H10(g)=a-C4H9Cl+b-C4H9Cl+Delta H-r the enthalpi es of reaction are derived as +5.3(mezo-) and +5.5(d, l-) kJ mol, whic h are closed with that of 1,2-dichlorobutanes also coincide with the c alculation results of our ''Electrostatic Bond Energy Scheme''.