This blog has not been updated for a while, and that’s because I’ve been sharing posts via Facebook using infographics from Compound Interest! But as of this term, I shall begin linking the posts from Facebook over here.
To begin with, let’s take a look at the article regarding Pyrimidanes. At A-Level, you will most definitely be taught about the pyramidal shape of P4 (white or yellow phosphorus). There may be some chelating compounds that you may encounter that have a similar shape, but the mysterious thing about these Pyrimidanes lay in the geometry.
Using VSEPR, an atom of carbon would prefer to form bonds that would be tetrahedral in shape. Limiting carbon to 3 bonds would violate the rules of valency.
The above diagram was taken directly from the site for the article regarding Pyrimidanes, and the curious geometry of both the covalent and ionic forms is seen. Yes, the carbons have 4 bonds in the covalent form, but the bond angle would not be 109.5 degrees as expected. There would be some strain on the compound structure due to the near 90 degree bond angles in the base (although even cyclopropane compounds exist).