Is SF2 Polar or Nonpolar?

Answer: SF2 is a polar molecule due to the presence of lone pair electrons on sulfur which force the molecule to adopt a bent configuration due to electron-electron propulsion. 

Due to the difference in electronegativity between Fluorine (3.98) and Sulfur (2.58), the molecule has a weaker dipole moment because some negative charge is being pulled towards the fluorine ends causing a little bit more of an even distribution of charge within the molecule. Although this author attempted to locate verifiable information about the boiling and freezing point of this molecule, this was not readily available due to the inherent instability present within the molecule. Due to the opposing regions of negative charge (one due to electronegativity and another due to lone pair electrons), the molecule is extremely unstable and readily "decomposes" into the molecule S2F4. In this new structure two SF2 molecules combine and form a double bond in between them.

S2F4 has a melting point of -98˚C and a boiling point of 39˚C. However, these numbers are probably not representative of those for SF2 because of the much larger structure (i.e. the newly formed molecule has many more electrons) and because the region of negative charge due to lone pairs has been essentially removed/cancelled away by the double bond.

For a reference point, the structure of SF2 is similar to that of H2O in terms of its configuration due to the same kind of electron-electron repulsion. Feel free to check out the Lewis Dot Structure of H2O and information related to its polarity.

SF2 Ball and Stick Model
SF2 Ball and Stick Model. Created with MolView.
What else is interesting about this compound? 

The bonding angle for SF2 is approximately 98˚ which is less than that of water (H2O) which has a bonding angle of 104.5˚. This is most likely also a result of the more negative fluorine dipoles which themselves are repelled from the lone pair electrons by negative-negative charge repulsion. This is as opposed to water where the partial positive hydrogen poles are more attracted to the negative lone pair electron region.

No comments:

Post a Comment