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How to Name Carbon Compounds: Alkanes, Alkenes, and Esters

Updated on April 18, 2012
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Carbon is so important to life on Earth due to its ability to form long chains. the first step in naming a carbon compound is to count the number of carbon atoms in the longest continuous chainThe next step is to check for the presence or absence of double (or triple) bondsThen look for functional groups. In this molecule, the functional group -COOH (the carboxyl group) is present, making it a carboxylic acid. The type of molecule determines the suffix of the name.
Carbon is so important to life on Earth due to its ability to form long chains. the first step in naming a carbon compound is to count the number of carbon atoms in the longest continuous chain
Carbon is so important to life on Earth due to its ability to form long chains. the first step in naming a carbon compound is to count the number of carbon atoms in the longest continuous chain | Source
The next step is to check for the presence or absence of double (or triple) bonds
The next step is to check for the presence or absence of double (or triple) bonds | Source
Then look for functional groups. In this molecule, the functional group -COOH (the carboxyl group) is present, making it a carboxylic acid. The type of molecule determines the suffix of the name.
Then look for functional groups. In this molecule, the functional group -COOH (the carboxyl group) is present, making it a carboxylic acid. The type of molecule determines the suffix of the name. | Source

Why is Life "Carbon-Based"?

Carbon is the basis of life on Earth. Carbon forms long chains and rings and has four free electrons in its outer electron shell. Carbon atoms make four bonds each due to the four free electrons in its outer shell. Where electron pairs are shared between two atoms, a covalent bond is formed. These bonds are very stable but are still reactive. These two properties combined allow for complex molecules to be formed based on a carbon skeleton:

  • Carbohydrates
  • Proteins
  • Nucleic Acids
  • Fats

The simplest carbon compounds are hydrocarbons - molecules made of hydrogen and carbon only. These are further broken down into alkanes and alkenes.

Naming Carbon compounds forms a large part of GCSE examinations - these questions are often worth several marks for a rather straightforward question. In my experience teaching chemistry, however, I have found that students often struggle with the specific nomenclature related to naming these molecules.

Naming Carbon Compounds 1

Number of Carbon Atoms
Prefix
1
meth-
2
eth-
3
prop-
4
but-
5
pent-
6
hex-
7
hept
8
oct-
9
non-
10
dec

How to Name Alkanes

When the spine of a hydrocarbon contains single covalent bonds only, it is known as an alkane. The name of an alkane always ends with the suffix '-ane.' The start of the name depends on how many carbon atoms are found in the spine of the molecule. For example, a hydrocarbon with two carbon atoms containing only single covalent bonds would be called ethane.

Alkanes are described as saturated hydrocarbons because they only have single bonds. The molecule contains the maximum possible number of hydrogen atoms per carbon atom.

Naming Carbon Compounds 2

Carbon Compound
Suffix
Alkanes
-ane
Alkenes
-ene
Alcohols
-anol
Carboxylic Acids
-anoic acid
Esters
-yl -anoate

How to Name Alkenes

When the spine of a hydrocarbon contains one or more double covalent bonds between two adjacent carbon atoms, the molecule is known as an alkene. The name of an alkene always ends with the suffix '-ene.' Once again, the start of the name depends on how many carbon atoms are found in the spine of the molecule. For example, a hydrocarbon with 4 carbon atoms containing a double covalent bond would be called butene.

Alkenes are described as unsaturated hydrocarbons because they have one or more double bond (two pairs of electrons shared between two atoms.) The carbon atoms are not bonded to the maximum possible number of hydrogen atoms.

Alkenes are very good at joining together to produce a new substance. This process, known as polymerisation, is due to the reactivity of the the Carbon-Carbon double bond (C=C). This process is how compounds such as plastics are made.

Alkenes can be distinguished from alkanes by testing with Bromine water. Due to their double bond, alkenes react with the bromine water and decolourise it; alkanes have no effect:

"If it's an alkane, it stays the same. If it's an alkene, no colour is seen"

With a Carbon chain of 2 ending in a hydroxyl group (-OH) this compound is none other than ethanol - the only alcohol safe for human consumption.
With a Carbon chain of 2 ending in a hydroxyl group (-OH) this compound is none other than ethanol - the only alcohol safe for human consumption. | Source

How to Name Alcohols

Alcohols are another group of Carbon Compounds: the alcohol consumed by humans is also known as ethanol. You recognise alcohols due to the presence of the hydroxyl functional group (-OH) at the end of a carbon chain. Naming this carbon compound follows the (now familiar) rules according to IUPAC. Count the longest continuous carbon chain to gain the prefix, then add the suffix -anol. If the longest carbon chain was 6 atoms long with a hydroxyl group at the end of the chain, the compound would be called hexanol.

IUPAC

A marker104 tw alexander drive Research Triangle Park, NC 27709, USA -
104 T W Alexander Dr, Durham, NC 27711, USA
get directions

The location of the International Union of Applied and Pure Chemistry - the body responsible for naming chemical compounds

How to Name Esters

Esters are pleasant smelling compounds created by reacting an alcohol with a carboxylic acid. These compounds are used in perfumes and are found naturally in fruits - pears are particularly ester-rich. The ester that gives that wonderful pear smell is ethyl ethanoate, and is made by reacting ethanol with ethanoic acid:

ethanol + ethanoic acid → ethyl ethanoate + water

Esters are tricky to name if you do not know how they are made. The first part of the name comes from the alcohol (____-yl), the second part of the name comes from the acid used (______-anoate). For example, if you react methanol and ethanoic acid, the resultant ester is methyl ethanoate.

If you react propanol and butanoic acid, the resulting ester is named - you guessed it - propyl butanoate!

(The name can be deduced from its structure - but that's the subject of another hub)

A Festive Review: Naming Carbon Compounds

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    • Marcy Goodfleisch profile image

      Marcy Goodfleisch 5 years ago from Planet Earth

      What a great guide! I hope this gets passed around among kids in science classes - it's short, informative, and easy to understand! (Where were you when I needed you??).

      Voted up!

    • ib radmasters profile image

      ib radmasters 5 years ago from Southern California

      That was very interesting and it seems easier than when I was taking chemistry in high school and college.

      Thanks

    • StellaSee profile image

      StellaSee 5 years ago from California

      Ahh I still need to take ochem..hope it's not as bad as what the rumors say! I think this hub will make it easier to remember naming though :D

    • TFScientist profile image
      Author

      Rhys Baker 5 years ago from Peterborough, UK

      The rules are easy, but it takes them being explained in a straightforward way for students to realise this. The great thing about these rules is that they apply to naming simple and complex molecules.

      I'm glad this was useful and interesting to you all

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