 this is another one you can see this one has one two three four different carbons so this one is not propanoic acid it's got full carbons so therefore it would be butte and you can see the acid group on the end here so the double bonded oxygen and then the hydroxyl group so an O and an H here which creates a C O OH functional group and this functional group is characteristic of the acid so that makes it butte and noic acid this particular molecule also goes by the common name of butteuric acid it has a particularly strong smell it's almost mandatory if you're going to study organic chemistry that you will encounter this particular molecule at some point and let me tell you you'll know when you do a lot of the acids have more common names so for example if I break this molecule in half and just create this little one here here's one that you're very familiar with as Linda would call it chikoo the CH3 and the C double OH is our chikoo it's two carbons with an acid function functional group so because it's two carbons with the acid functional group it's called ethanoic acid now we have encountered it more commonly or we've named it more commonly as acetic acid acetic acid is the correct name but it's not the preferred OUPAC name the preferred OUPAC name is ethanoic acid it's also the key component in vinegar so this is a very important group of acids methanoic acid which is this one is also goes by the name of formic acid and it's an acid that's associated with ants the substance that they release when you die each what the thing with this group is they're characterized by the fact that all of them have a fairly strong aroma and as we use these acids in some of our chemical reactions later on in this module you will encounter that particular factor so again you're just looking for the C double OH which is your functional group and the total number of carbons we have all together tells us about the name so again in this case this would be methanoic acid as it's preferred OUPAC name