Victor Meyer's test tells primary, secondary, and tertiary alcohols apart using nothing but colour — blood red, blue, or no colour at all. Below: the full mechanism, the classification it relies on, and a quiz to test what sticks.
An alcohol is an organic compound in which a hydroxyl group (–OH) is bonded to a saturated carbon atom, written generally as R–OH. That single –OH group governs almost everything about how the molecule behaves: its boiling point, its solubility in water, and — most importantly for this page — how it reacts with a specific sequence of reagents.
Not all alcohols are built the same way. The carbon carrying the –OH group can be attached to one, two, or three other carbon groups, and that difference alone is enough to change the colour a molecule turns during Victor Meyer's test. Before the test makes sense, the classification has to.
Chemists classify alcohols by how many carbon groups sit on the carbon bearing the –OH. That number is called its degree, and it's the entire premise Victor Meyer built his test around.
The –OH carbon is attached to only one other carbon chain (and two hydrogens). Least hindered, most reactive toward oxidation.
The –OH carbon sits between two carbon chains and one hydrogen. Intermediate reactivity and steric bulk.
The –OH carbon is bonded to three carbon chains and no hydrogen. Most hindered — and, as the test shows, unreactive at the final step.
Each alcohol is pushed through the same four-step sequence. Primary and secondary alcohols make it all the way to a coloured end point; tertiary alcohols stall at the final step. Hover any card for the chemistry behind it.
Pick an answer — you'll see immediately whether it's right.