[MUSIC] Lesson five is titled models and lingo. So it might seem a bit odd that we
start the first part of this lesson with the slide entitled, IUPAC Nomenclature:
Machines Do It Better. But in reality, this is the case. By using a chem drawing
tool such as MarvinSketch, we can generate the IUPAC Nomenclature for any organic
compound with a simple click of the button. And if we were to modify the
structure of hexane, such as by adding a benzene ring to one of the metal groups,
we could see that addition of this benzene ring immediately changes the name of this
compound to pentylbenzene. While it may not be important for you to be able to
apply IUPAC Nomenclature and name a very complex organic molecule. It is important
to be able to name certain organic compounds that are present within these
very complex molecules we will see in the future. We can begin by systematically
naming alkanes which are hydrocarbons that contain only single bonds. First, let's
consider straight-chain n-alkanes, which are alkanes that are not in cyclic
structures and do not have any branches. All alkanes will follow this molecular
formula. A straight-chain n-alkanes containing one carbon atom is known as
methane, and an alkane that contains two carbon atoms is known as ethane. If we
apply the formula above to ethane or any other strait tune alkane for that matter
we can see that ethane has two carbon atom and if we do 2 times 2 is 4 plus 2 equals
6 we should expect to have 6 hydrogen atoms which is the case we see here and
the case that we will see with all straight-chain n-alkane structures. The
rest of this lesson requires you to become familiar with the nomenclature given to
straight-chain n-alkanes. A three carbon straight-chain n-alkane is known as
propane, while a four carbon one is known as butane. And if we return to the ideas
that we learned about in lesson four, we can remember that in skeletal structures,
carbon atoms are not explicity labeled and carbon to hydrogen bonds are implied. We
can use the fact that in order to remain neutral, a carbon atom must have four
bonds associated with it to predict how many implied hydrogens surround each
carbon atom in the structure. Finally, this slide provides the nomenclature given
to other straight-chain n-alkanes. It is worth memorizing, because even though I
mentioned in the first slide that assigning names to very complex organic
molecules not needed because machines can do it for us. Many organic compounds
derive their names from the alkanes that we went over in this lesson.
And it will be very helpful for you to know these when beginning to interpret
organic structures.