Question #85060
1 Answer
I assume you are referring to the molecular or structural formulas of these chemical families as opposed to their properties. See my comments below...
Explanation:
What you must do is look carefully at the structure that surrounds the functional group.
All of these molecules have a carbonyl group - a carbon atom joined to an oxygen atom by a double bond. In an aldehyde, this carbon will be bonded to another carbon (or an alkyl group to be more precise) and also to a hydrogen.
In a ketone, the carbon of the carbonyl group will be bonded to two other carbons (or larger alkyl groups which need not be the same).
In an organic acid, we find the carbon bonded to an alkyl group and to a hydroxyl group (-OH). This is also called a carboyxl group.
Finally in an ester, the carbon is bonded to an alkyl group and to an oxygen atom, which in turn is bonded to another alkyl group.
Check this Wikipedia page for diagrams
