Question

Naming Organic Compounds Tutorial

Answer 1

IUPAC nomenclature is a system of rules designed to give every compound an unambiguous name. Like a name for a person (ex. John Doe Smith) which is divided into first name, middle name, and surname, a chemical compound has a name that is divided into parts: Prefixes, Parents, and Suffixes

Answer 2

The simplest compound to name is a hydrocarbon known as an alkane, which consists of carbon chains bonded to hydrogen atoms

Answer 3

To name a simple chain alkane, use a prefix designating the number of carbons, then append "ane"

for example, the above carbon chain would be "heptane" because hept- is the latin prefix for 7

Carbons 1-4 get special names under IUPAC, and the rest follow Latin prefixes.

1 = methane
2 = ethane
3 = propane
4 = butane
5 = pentane
6 = hexane
7 = heptane
8 = octane
9 = nonane
10 = decane
11 = undecane
12 = dodecane
etc.

Answer 4

Alkanes can also come in aromatic rings. To name a ring, add "cyclo" to the beginning of the chain name.

So, for a chain of 7 carbons, the compound name is "cycloheptane"

Answer 5

Alkanes can also have parts that branch off, like a tree. These "branches" are named by changing the -ane to -yl and keeping the original prefix.

For branches of 4 carbons or fewer, the names are:

methane -> methyl
ethane -> ethyl
propane - > propyl
butane -> butyl

Answer 6

Now, we could append the "ethyl" name to the "heptane" name to get "ethyl-heptane" but there is another problem! If we attach the ethyl group to different positions on the carbon, we get different compounds. IUPAC must give a unique name to each compound so we must specify where the group is located.

To do this, we use "locants", which are numbers that describe the location of an atom or functional group.

Answer 7

To determine locants, we start by numbering the carbon chain to give the functional group the lowest possible number. Since our group is closer to the left side, we start numbering from the left.

Answer 8

The ethyl group is on carbon 3. The compound is thus named 3-ethylheptane. Notice that the locant comes before the functional group.

Answer 9

If we have two or more of the same functional group, we must specify the location of each individual group using multiple locants, even if the groups are on the same carbon. In the compound name, we add a prefix to specify how many of that group there are. For example, if we add some more groups to our compound...

Answer 10

When naming compounds, it is helpful to write down the individual "pieces" and assemble them in the correct order.

We have:

2 ethyl groups on carbon 3, so we must have 3,3-diethyl
1 methyl group on carbon 2, so we must have 2-methyl

When putting the parts in order, we prioritize by alphabetical order of the functional group, ignoring prefixes. Therefore, diethyl is listed before methyl because e comes before m.

Answer 11

When there are many branches on the alkane, it can be difficult to determine where to start numbering. The rule is: number the longest carbon chain, and give each functional group the lowest numbers possible at the first point of difference.

Answer 12

If we attach a halogen atom to an alkane, we get an alkyl halide. We designate this by attaching a prefix (chloro, bromo, fluoro, etc.) to the chain name, with the appropriate locant. For numbering, follow alphabetical order.

Answer 13

Alcohols work a little differently. When you see an -OH group, change the suffix of the parent name from -ane to -ol. So, heptane becomes heptanol. Use a locant to locate the -OH group.

(As a side note, if the locant is 1 it is sometimes omitted.)

For numbering, alcohols have priority over other groups, so give the alcohol group the lowest number possible. Make sure the -OH group is attached to the longest carbon chain.

Answer 14

Cyclic alkanes follow similar rules to branching chain alkanes. Give the substituents the lowest number possible and list them in alphabetical order.

Answer 15

When two rings are fused together they are named as "bicycloalkanes". The parts of a bicyclo alkane are labeled as follows:

Answer 16

Start at one bridgehead, number along the longest bridge, then along the next highest bridge, and then number the middle bridge last.

Answer 17

Start with the compound name bicyclo[#.#.#] where the # are the lengths of the bridges in descending order.

Answer 18

Compounds with at least one double bond but no triple bonds are called "alkenes". They are named similarly to alkanes with one additional rule: give the carbon atoms of the double bond the lowest number possible.

Answer 19

For compounds with double bonds and alcohol groups, name as "alkenols" and prioritize the alcohol group when numbering.

Answer 20

Alkenes can also be designated as E or Z depending on the location of the functional groups relative to the double bond. Assign priority to the groups based on molar mass (see Ingold priority). If the highest priority groups are on the same side of the double bond, designate as Z. If the highest priority groups are on opposite sides of the double bond, designate as E.

Answer 21

Compounds with at least one triple bond are named as "alkynes". The numbering is given to give the alkyne carbons the lowest numbers. However, if there are double AND triple bonds present, the double bond is prioritized.

Answer 22

That's all for my tutorial, hope you found it useful! Feel free to tag me with any questions. Upon request, I can add more examples to the end.