Heats of combustion, formation, and insomerization of ten C4 hydrocarbons

Abstract

The heats of co mbustion of ten C4 hydrocarbons were meas ured b y combustion of t he gaseous hydrocarbon in a flame at constant pressure in a glass reaction vessel in a calorimeter. The calorimeter system was calibrated by means of electrical e ne rgy.The exp erimental data yielded the following values for the standard heat of combustion, -t:J.Hco , at 25° C and co nstant press ure, of the gaseous hydrocarbon in gaseous oxygen to form gaseo us carbon dioxide and liquid wate r, with all t he reactants and products in their thermodynamic standard reference states, in k cal/mole : n-butane, 687 .42 ± O.15 ; 2-methylpropane, 68S.37 ± O.11 ; I-butene, 649.33 ± O.18 ; cis-2-bute ne, 647.6S ± O.29 ; trans-2-butene, 646.90 ± O.23 ; 2-methylprope ne, 645.19 ± O.2S ; 1,2-butadiene, 619.93 ± O.13 ; 1,3-butadiene, 607.16 ± O.18 ; I-butyne, 620.64 ± O.20 ; 2-buty ne, 61S.84 ± O.23 .Values of hea ts of isomerization, formation, and hydrogenation were derived from these dat a .

Enthalpy of formation of phosphorus pentachloride; derivation of the enthalpy of formation of aqueous orthophosphoric acid

“…At 24°C, the thermometer had a resistan ce of 29.8966 0, and a temperature coefficient of 0.100767 O/°e. The electrical energy was measured by a circuit basically the same as that described in [4,5, and 6J-Steady current from a bank of large storage batteries was switched by a solenoid, as required, between the calorimeter heater and a dummy coil of similar resistance. A steady EMF of 120 V dc was applied to the busbars in all calibration experiments.…”

“…Potential drops across the resistors were measured using a White double potentiometer [4] (range 0 to 100 m V), which, at the conclusion of the series of runs, was calibrated for internal consistency of steps on the two largest decades_ The dial corrections (max: 1.3 /-tV) agreed well with an absolute calibration made in 1943 by the Resistance Section , NBS. An auxiliary circuit consisting of a 100-0 and a 1,000-0 standard resistor was used to establish a 100/1100 fraction of standard cell voltage for determination of potentiometer ratio [5] at the conclusion of each run. Interpolations of the last-dial readings to zero galvanometer deflection, cofrection for external parasitic emf (usually zero, sometimes barely detectable), dial corrections (from the present calibration), and potentiometer ratio (0.9998958 to 0.9999586) were applied.…”

Heat of formation of boron trichloride

“…The poten tials wer e measured with a W'enner p oten · tiometer which was b alance d against a th ermostated Weston standard cell [3]. Timing of the experiments wa s accomplish ed by refere nce to th e standard second signals produced at th e Bureau.…”

“…The values for the heats of hydrolysis and the corresponding standard heats of formation of liquid BCl3 are summarized in table 3. The crystalline form of boron at 25° C has been taken as the standard reference state.…”

Isomerization of Cyclooctadiene to Cyclooctyne with a Zinc/Zirconium Heterobimetallic Complex

“…From gas-phase calorimetry measurements, the D f H o values for 1,3-butadiene and 2-butyne are 26.7 AE 0.2 and 34.7 AE 0.2 kcal mol À1 respectively. [3] Diene-to-alkyne isomerization becomes increasingly unfavorable within small or medium carbocycles;t he product would be expected to incorporate significant ring strain ( Figure 1). [4] Consistent with these data, the microscopic reverse reaction, alkyne-todiene isomerisation, can be catalyzed by rhodium/BINAP, [5,6] ruthenium hydride, [7] or gold(I) complexes.…”