Winter Final 2013 6B

[104469125]

I was wondering how to approach this question: A facial cream known to assist with dry skin has the following common name ingredients listed: stearic acid; glycerin; and acetyl alcohol. Their restive IUPAC names are: octadecanoic acid; propane-1,2,3-triol; and hexadecan 1-ol. Write the common name and IUPAC name next to each structure.
There are three given structures but I'm not sure how to match the different names to the structures.

[Jessica Phan 2N]

To match the names with the structure, you need to look over all the functional groups and know their general compound name and how the endings change for those functional groups. For instance, the carboxyl group is -COOH and since it often acts like an acid it is often called a carboxylic acid. For carboxylic acids, the root hydrocarbon name ending in -e is changed to -oic acid. We can see that the second structure has the -COOH group attached to it. Hence, we know that the IUPAC name should have an -oic acid at the end, hence we can conclude that octadecanoic acid matches with the second structure. The same goes for learning what the functional group of alcohol looks like and how the ending is changed for the IUPAC named. For me looking at the numbers and where the functional groups are attached to helps me eliminate structures if I don't know how to name them for not knowing the prefixes. For the common name, I used process of elimination. For example, since cetyl alcohol has the word alcohol on it I know the 1st and 3rd structure is more likely to have that name than the second structure which we concluded is a carboxylic acid. I noticed that stearic acid has the word acid in it, so it is more likely to be matched with the carboxylic acid. Fortunately, for me, I read about glycerin in the introduction to organic chemistry course reader so I knew that was what it matched with.