Effective Visualization of Implicit Hydrogens with Prime Formulae

The ability to extract structural information from a drawing of a molecule is key to being successful in organic chemistry. One source of difficulty for novices in interpreting structures is that hydrogens bound to carbon are represented implicitly in the often-used line-angle structures. Other representations that explicitly show hydrogens, such as Kekulé structures or condensed formulae, are less efficient to draw than line-angle structures and can therefore make tasks such as proposing a mechanism prohibitively long. A new type of formula, the prime formula, is disclosed in this article as an efficient way to draw chemical structures with hydrogens being clearly represented. The number of hydrogen atoms on each carbon are represented by superscripts with ° = 0 H, ′ = 1 H, ″ = 2 H, and ‴ = 3 H. Pre-treatment and post-treatment data was collected and compared to a control group. By viewing a question in prime formula vs line-angle formula, an improvement in student performance with a significance of p_tukey = 0.008 and df = 63.3 was observed for mapping atoms of a starting material onto a product, a key skill for proposing complex arrow-pushing mechanisms. An increase in performance with a significance of p = <0.001 and df = 57.3 was obtained for determining the number of stereogenic centers in a complex molecule. Data collected also support that it is efficient to learn how to interpret and draw prime formulae.