Science Poetry

IR Spectroscopy

“Motions molecular
Lead to conjecture
Re: key architecture of functional groups…
IR spectroscopy;
Target topography:
Features are quantified through linked Law of Hooke.” 

The 11 July 2019 poem discusses another kind of spectroscopy commonly used in organic chemistry coursework: infrared (IR) spectroscopy, which uses infrared light waves.  IR waves are shorter (and higher-energy) compared to the radio waves of NMR spectroscopy, but they are still longer (and lower-energy) than the light waves associated with visible light.   

“Motions molecular/ Lead to conjecture/ 
Re: key architecture of functional groups…”
A molecule is a chemical compound in which atoms are bonded to one another covalently, by sharing electrons.  One of the ways in which chemists think about these bonds is via the model of a tiny spring.  Springs can compress and elongate: bond lengths can shorten and lengthen, in “motions molecular.”  The energies involved in these changes in bond length are characteristic depending on what types of atoms are bonded together (what is at either end of the “spring”?).   Functional groups are groups of atoms that dictate how a molecule behaves.  For instance, an ether functional group contains an oxygen atom bonded to a carbon atom on either side.  Infrared (IR) spectroscopy provides information regarding the functional groups that a molecule contains: identifying the “key architecture” of that molecule.   

“IR spectroscopy;  /  Target topography: /
Features are quantified through linked Law of Hooke.”

NMR spectroscopy can provide precise evidence in support of the structure of a chemical compound, but IR spectroscopy is more generally useful.  The metaphor I use in this poem is a topographical map: the major landmarks (here, the functional groups of the molecule) are the most evident data.  While these calculations are typically not explored in detail until more advanced chemistry classes, it is also possible to predict the specific numbers behind a given piece of IR data: to quantify the features of the molecule.  This is done by analyzing the masses of the atoms involved and the force constant of the pertinent bond.  The calculations employ a model called Hooke’s Law, often introduced in a “linked” prerequisite: a student’s physics coursework.