Fluoromethane, boiling point

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). ... 

Table 1.5 Dipole moments ( x) and boiling points of fluoromethanes and fluoroethanes ...

Figure 1.5 Boiling points (°C gray bars) and dipole moments (D , numerical values in italics) of methane and the different fluoromethanes CH4. F [2].

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