Bromine, thermodynamic data

Br(g) from the thermodynamic data provided in Appendix 2A. (b) What is the vapor pressure of liquid bromine (c) What is the partial pressure of Br(g) above the liquid in a bottle of bromine at 25°C (d) A student wishes to add 0.0100 mol Br2 to a reaction and will do so by filling an evacuated flask with Br2 vapor from a reservoir that contains only bromine liquid in equilibrium with its vapor. The flask will be sealed and then transferred to the reaction vessel. What volume container should the student use to deliver 0.010 mol Br2(g) at 25°C ... 

In conclusion, only Scheme 3 matches the kinetic and thermodynamic data, showing that the CTC s are essential intermediates of the bromination reaction. 

The standard potentials of the reactions involving bromine species with oxidation number of +1 or higher are calculated from thermodynamic data. 

Less is known about the anhydrous bromine-containing oxysalts than about the corresponding compounds of chlorine and iodine. This is true both with respect to the total number of such salts, as well as the information available on each salt. Since 1974, when the last review of these compounds was published,1 the situation has changed only slightly, with the number of known bromites increasing from 2 to 3, bromates from 15 to 17, and perbromates from 3 to 8. There are still no thermodynamic data above 298 K. Consequently, this chapter is fairly brief, includes no high-temperature equilibrium calculations, and updates qualitative and semi-quantitative information using material published since 1972. 

Use the thermodynamic data in Appendix K to estimate the normal boiling point of bromine, Br2. Assume that AH and AS do not change with temperature. 

Prop.t (Far) IR, assignment (675) and NMR (I32I) spectra, thermodynamic data (305) Anal. detn. by coulometric detn. after bromination (I696). 

According to (57), the main driving force for the reaction in non-protic media is the formation of a tribromide ion from bromine and the developing bromide. Kinetic (Ruasse et al., 1986) and thermodynamic (Bienvenue-Goetz et al., 1980) data on equilibrium (58) are therefore relevant to the effect of non-protic solvents on bromination rates. 

P (c, red). The exact thermodynamic status of the solid forms of phosphorus other than yellow has not yet been determined. The vapor pressure of red phosphorus was measured by Chapman1 and Troost and Hautefeuille1 and the latter calculated, from the difference in the temperature coefficients of the vapor pressures of the yellow and red forms, the heat of transition from yellow to red to be 4.2 at 700°. From the difference in the heats of combustion of the yellow and red forms of phosphorus, Giran1 found T=3.7. A more direct measurement of the heat of transition is that from the data of Giran1 on the heats of reaction of the two forms with bromine in carbon disulfide, (2 = 38.79 and 43.01 for the red and yellow forms, respectively. These data yield T=4.22. Giran1 found that the so-called violet or black phosphorus had a heat of reaction of 38.56 with bromine in carbon disulfide. Apparently this form is thermochemically identical with the red form. 

The data for sulphur, bromine and iodine compounds in Table 20.1 are different from the data in the original paper. In Table 20.1 the elements in their stable form at 25 °C and 1 bar are taken as reference states, as is usual in thermodynamics in the original publication S2(g), Br2(g) and 12(g) were taken as reference state. 

Since the rate of enolisation generally determines the rate of bromination of a ketone [i2g], it should be possible to correlate bromination rates for steroid ketones with their rates of enolisation. These in turn should be related to the thermodynamic stabilities of the respective olefinic bonds, insofar as transition states for enolisation under acidic conditions resemble the structures of the enols (p. 154). The very limited kinetic data available [133,134] confirm this relationship for three 3a-cholestanones whose reactivity falls in the order C(3) > C(e> > C(7). This would reasonably be predicted from consideration of strain associated with the A -, A -, and A -double bonds, coupled with steric hindrance to the transition... 

A similar reaction process should occur for Br, because AGr° = -1.4 kj/ mol, but such a reaction is thermodynamically unfavorable for Cl" with a AGr° = +28.2 kj/mol. These data further indicate the conservative nature of Cl in seawater and the incorporation of iodine and bromine into organic matter in the ocean (3, 31). 

Write a mechanism for the radical bromination of the hydrocarbon benzene, CgHg (for structure, see Section 2-4). Use propagation steps similar to those in the halogenation of alkanes, as presented in Sections 3-4 through 3-6. Calculate AH° values for each step and for the reaction as a whole. How does this reaction compare thermodynamically with the bromination of other hydrocarbons Data DH° (CgHs-H) = 112 kcal mol DH° (C Hs-Br) = 81 kcal mol . Note the Caution in Exercise 3-5. 

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