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Definitions of Vocabulary

Alkanes, Alkenes, Alkynes

Models and Naming of Organic Molecules

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Models and Naming of Organic Molecules

Basic Naming Rules

For you to really understand this, you need an example. So, throughout this guide, I am refering to this molecule when I am explaining. *Note: All hydrogens are understood to exist.*

The example. If you can't see it, you're screwed.

  1. Find the longest chain. This chain may just be a single straight line or it may turn. Count the number of carbons in this chain. This will be the last piece of your name.
  2. Are there double/triple bonds? If there are, then make sure that you have the appropriate suffix (-ene for double bonds, -yne for triple bonds). In this example, there are eight carbons in the longest chain, and there is a double bond, so the last piece of the name will be "octene".
    • If you have multiple bonds, then you must also add a number in front of this last name.
    • Count your carbons. On the carbon that has the multiple bond, put its number in front of the last name. Since the double bond in the octene is on the third carbon, then the last piece of the name will now be 3-octene.
  3. Now look at substituent groups. Find the group that has the lowest name alphabetically. Here, we have one ethyl group and two methyls. Since ethyl comes before methyl in the alphabet, we will look at it first.
    • How many of this molecule are attached? Here, we have only one ethyl, so we will write "ethyl". There are two methyls, so attach a prefix and write "dimethyl".
    • What are the positions of the groups? The ethyl is attached to carbon 5, so we will write "5-ethyl". The methyl groups are attached to carbons 2 and 6, so we write "5-ethyl 2,6-dimethyl".
  4. If you have any cis or trans, they go at the very beginning of the name.
  5. Now put the pieces together. The piece describing the substituent groups goes first. The piece describing the longest chain goes last. So, the name of this molecule is "5-ethyl 2,6-dimethyl 3-octene".


Naming of Functional Groups

Basic Functional Groups
Prefix/Suffix Name Group added
N/A Hydroxyl - OH
N/A Carbonyl - C = O
N/A Carboxyl Carbonyl bonded to hydroxyl
More Complicated Functional Groups
Prefix/Suffix Name Group added Example
-ol Alcohol Hydroxyl group Ethanol A picture of ethanol.
-amine Amine - N H2 Cyclohexamine A picture of cyclohexamine.
-one Ketone Carbonyl group bonded to two other carbons 2-propanone A picture of 2-propanonone.
-oic acid Carboxylic Acid carboxyl group Ethanoic acid A picture of ethanoic acid.
-oxy- Ether Two carbons bonded by an - O - Ethyl ether A picture of ethyl ether.
-ate Ester A carboxyl group where the hydrogen of the hydroxyl is replaced with an alkyl group. Methyl ethanoate A picture of methyl ethanoate.
-amide Amide A carboxyl group where the hydrogen of the hydroxyl is replaced with a nitrogen atom bonded to other atoms. Ethanamide A picture of ethanamide.