Oxidation of aldehydes and ketones.

Let's take a moment to practice assigning oxidation numbers in the context of the oxidation of aldehydes. Potassium permanganate (KMnO₄) or chromic acid (H₂CrO₄) oxidize aldehydes (and alcohols) to form carboxylic acids. In the initial state in potassium permanganate, the oxidation state of manganese is +7 and in chromic acid, the oxidation state of chromium is +6. In an aldehyde, the oxidation state of carbon is +1. After the reaction, the carboxylic acid carbon will have an oxidation state of +3.

Do you understand the rationale behind the assignment of a +1 oxidation state to aldehyde carbon and +3 to carboxyl carbon? Look at the covalent bonds and assign control of the electrons based on electronegativity.