Chomp!
Vivien Wang
Sophomore, LSA
Medium
Digital illustration
Abstract
The highly reactive carbonyl functional group consists of an oxygen double-bonded to a carbon. The electron-hungry oxygen eagerly bites passerby reactants, freeing its carbon to form new bonds.
To prevent this “hydra head” from growing more heads when synthesizing chemical comounds, organic chemists use protecting groups like the “blue double-headed serpent” ethylene glycol. Its two oxygen atoms chomp onto the “hydra neck”double bonds. Meanwhile, two hydrogen “birds” carry the former oxygen as water.
After completing other reactions, or modifying the hydra’s body, chemists simply remove the protecting group, restoring the original carbonyl!
Carbonyl functional groups (an oxygen atom double-bonded with a carbon atom) is an extremely reactive species. The electron-hungry oxygen is always eager to snap up electron-generous passerby’s, alleviating its carbon of one bond to bind to another molecule as well. If this were to happen, we would be left with a singly bonded oxygen and carbon that have been bonded to additional molecules.
How do we prevent this finicky carbonyl group from reacting unnecessarily during other reactions? In other words, how do we prevent a hydra from growing two heads?
To prevent the formation of unwanted products when synthesizing chemical compounds, organic chemists introduce a protecting molecule, in this case ethylene glycol (blue double-headed serpent). Its two oxygen atoms (heads of the serpent) at the ends of its two-carbon chain to bite down on one of the double bonds of the carbonyl, preventing the severed necks of the hydra from forming new bonds. The former oxygen of the carbonyl group (original hydra head) is airlifted out of the picture by two tiny hydrogen atoms (birds) as a molecule of water, as this process is considered a dehydration reaction. The resulting structure is called a acetyl (if the original carbonyl was an aldehyde) or a ketal (if the original carbonyl was a ketone).
Once chemists are done with their reactions (other body modifications to the hydra), they simply remove the protective group using an aqueous acid (H3O+) through a hydrolysis reaction, restoring the carbonyl group to just a single head, like before!