Tuesday, September 8, 2009

Physical properties

Alkyl halides have little solubility in water but good solubility with nonpolar solvents, such as hexane. Many of the low molecular weight alkyl halides are used as solvents in reactions that involve nonpolar reactants, such as bromine. The boiling points of different alkyl halides containing the same halogen increase with increasing chain length. For a given chain length, the boiling point increases as the halogen is changed from fluorine to iodine. For isomers of the same compound, the compound with the more highly-branched alkyl group normally has the lowest boiling point. Table summarizes data for some representative alkyl halides. 
TABLE 1 Boiling Points (°C) of Alkyl Halides 
                         Flouride Chloride Bromide Iodine 
Group                   bp         bp              bp        bp 
Methyl             −78.4     −28.8        −3.6     42.5
Ethyl                −37.7       13.1         38.4       72
Propyl            −2.5        46.6           70.8     102
Isopropyl       −9.4      34             59.4        89.4
Butyl                32      78.4             101          130
Sec-butyl                     68              91.2         120
Tert−butyl                       51           73.3       100

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