Video Transcript
What is the correct IUPAC name of
this halogenated alkane? (A)
1-Fluoro-2-bromo-3-chloro-4-iodohexane. (B)
1-Fluoro-2-bromo-3-chloro-4-iodopentane. (C)
5-Bromo-4-chloro-6-fluoro-3-iodohexane. (D)
2-Bromo-3-chloro-1-fluoro-4-iodohexane. Or (E)
3-bromo-4-chloro-1-fluoro-5-iodoheptane.
The International Union of Pure and
Applied Chemistry, or IUPAC , is the international organization that’s in charge of
standardizing methods, measurements, and naming for chemists and other scientists
worldwide. And so they have developed standard
rules for naming halogenated alkanes. The first step in naming the
halogenated alkane above is to find the longest carbon chain. And you can see that all of the
carbons in this molecule form one single six-carbon long chain.
The second step is to number the
carbon chain from step one so that the carbons with halogens bonded get the lowest
possible number sequence. Basically, we have to number all of
our carbons one to six starting from either the left or the right side. And you can see that if we start
numbering our carbons at one from the right side, then the lowest number carbon
that’s bonded to a halogen is carbon number three. However, if we start numbering our
carbons from left to right, then the lowest number carbon that’s bonded to a halogen
is carbon number one. And since we’re looking to number
our carbons where the halogens bonded get the lowest possible number sequence, we
know that this is the correct way to number our carbons.
Next, since we have multiple types
of halogens that are bonded to the alkane backbone, we have to order them
alphabetically. It’s important to note that to name
a halogen atom as a substituent, you must use the root of each halogen name and add
the suffix -o. For example, chlorine becomes
chloro-. And so to put all four halogen
atoms in alphabetical order along with the correct substituent nomenclature, we
would put them in the order of bromo-, chloro-, fluoro-, and iodo-.
And so with this information, we
can begin to answer the question “What is the correct IUPAC name of this halogenated
alkane?” Because our root structure or
longest carbon chain is composed of six carbons, we’ll start with the root structure
hexane. Then, we can write out each halogen
atom in alphabetical order. And finally, in front of each
halogen atom, we write in the carbon number that each one is bonded to. And using this IUPAC method, we get
the answer of 2-bromo-3-chloro-1-fluoro-4-iodohexane. And so, we can identify the correct
answer as (D).
