Animated Solution for Chemistry - Organic Chemistry: The number of nitrogen atoms in a semicarbazone molecule of acetone is .......

Imagine you are in an organic chemistry lab, and you mix acetone with a reagent called semicarbazide. What happens next is a classic condensation reaction. The carbonyl oxygen of the acetone molecule teams up with two hydrogen atoms from the semicarbazide to form a water molecule, which is eliminated.

What is left behind is a beautifully crystalline solid known as acetone semicarbazone. These types of derivatives are incredibly useful for chemists because their sharp melting points help in identifying unknown aldehydes and ketones.

To answer our question, we don't need to do any complex math; we just need to look closely at the structure of the molecule we've formed. The chemical formula for acetone semicarbazone is $({\text{CH}}_3{)}_2{\text{C=N-NH-CO-NH}}_2$.

Let's take a walk through this molecule from left to right. On the far left, we have the two methyl groups from the original acetone molecule attached to a carbon atom. This carbon is double-bonded to a nitrogen atom. That's our first nitrogen!

Moving further right along the chain, this first nitrogen is single-bonded to another nitrogen atom, which is part of an $\text{NH}$ group. That's our second nitrogen.

Finally, after passing through the carbonyl carbon ($\text{C=O}$), we reach the end of the molecule, which terminates in an ${\text{NH}}_2$ group. This gives us our third and final nitrogen atom.

So, if we tally them all up: one from the imine-like double bond, one from the secondary amine linkage, and one from the terminal amide group. The total number of nitrogen atoms in a single molecule of acetone semicarbazone is exactly 3.