Boiling point of halogens

Balaban, A. T., et al., Correlations Between Chemical Structure and Normal Boiling Points of Halogenated Alkanes C1-C4. J. Chem. Inf. Cornput. Sci., 1992 32, 233-237. 

Balaban, A.T., N. Joshi, L.B. Kier, and L.H. Hall. 1992a. Correlations between chemical structure and normal boiling points of halogenated alkanes Q - C4. J. Chem. Inf. Comput. Sci. 32 233-37. 

Figure 1.4 Boiling points of halogenated acetic acids as a function of refractive index. Squares are fluorinated acetic acids.

Fig. 17-6. The melting and boiling points of some molecular compounds and the halogens. A. The inert gases and the halogens. B. The carbon compounds of formula CX,.

Using the data from Table 19-11, plot on one set of axes the melting and boiling points of the halogens versus row number. 

Self-Test 15.5B Explain the trends in the melting points and boiling points of the halogens. 

Boiling points of the halogens increase with the number of electrons. 

Kinney s method was used In the author s lectures for several years but did not prove to be exploitable since it does not allow estimation of boiling points of many substances such as halogenous derived substances. On the other hand, Benson s method proved to be very useful and will be discussed in Chapter 2 ( Stability ). 

The attractions get stronger as the molecules get bigger in size and have more electrons. The pattern of variation of boiUng points of different halides is depicted in Fig. 10.1. For the same allqrl group, the boiling points of allqrl halides deerease in the order Rl> RBr> RC1> RF. This is beeause with the inerease in size and mass of halogen atom, the magnitude of van der Waal forees Inereases. 

While the boiling points of chloro- and bromomethanes always increase according to the number of halogen atoms, this correlation does not exist in the case of fluoromethanes. The bp increases from CH4 to CH2F2 and then decreases until CF4 (Table 1.4). Indeed, a parallelism exists between boiling points and dipolar moments. A partially fluorinated compound will exhibit nonnegligible intermolecular interactions according to the importance of the dipolar moment (Table 1.5). ... 

Hydrofluoric acid in contact with water behaves anomalous when compared to the heavier halogens. The hydrogen-fluoride bond is relatively strong and ion pairs of the type H3 0+F exist rather than free hydronium ions [10]. Anhydrous HF is an electrically conducting liquid (3HF = H2F+ + HF2 occurs) with a normal boiling point of 19.5 °C. Scheme (1) summarizes the most important forms, the standard potentials in acidic aqueous media, and typical applications of fluorine. 

Boron, which occurs in the second period of the periodic system as a tervalent ion, is naturally very small (see Table F), and, in the compounds which it forms with the halogens, the boron ion will be completely shielded by the three halogen ions, so that the boron halides are thus compounds with low boiling points. Of the halogen ions, iodine, which contains the most electrons, is the largest. In aluminium iodide the three iodine ions will shield the aluminium ion, as also do the somewhat smaller bromine or chlorine ions in... 

The reason why boiling points of completely shielded compounds rise if the halogens are replaced by others with a higher atomic number will be dealt with later in Section 51. 

Halides of carbon, other than those given in Table XXXIV, are known, and mixed halogen compounds also exist the boiling points of these compounds are given in Table XXXV. In this series the boiling point rises by equal increments when one halogen in a compound is replaced by another, and the calculated values given in the table assume equal increments. It appears that the mixed... 

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