Simple Alkanes
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Simple Alkanes

 The simplest alkanes have two-part names. (More complex molecules will have additional parts as needed.) The first part of the name for a simple alkane tells how many carbon atoms are in the molecules. The second part is simply -ane to indicate single bonds only.

Ten of these alkanes are listed here. I would like you to learn these ten names and be able to associate each of those names with the molecular formula shown next to it, specifically the number of carbon atoms shown in the formula. You can memorize the number of hydrogen atoms if you want, but you can figure them out very easily when you need to, as you will see.
Name Molecular
Formula
methane CH4
ethane C2H6
propane C3H8
butane C4H10
pentane C5H12
hexane C6H14
heptane C7H16
octane C8H18
nonane C9H20
decane C10H22

 

You should notice that most of these names contain standard prefixes for numbers: pent for five, hex representing six, hept representing seven, oct representing eight, non for nine, and dec for ten. You are probably already familiar with most of those from the names of various geometric shapes like pentagons and hexagons. Although meth-, eth-, prop- and but- don't come from the same source, you will need to become familiar with those prefixes meaning one, two, three and four carbon atoms respectively.
pent- 5
hex- 6
hept- 7
oct- 8
non- 9
dec- 10

To review, the names of these alkanes are made up of two parts. The first part represents the number of carbons (that would be the meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, and dec-); and the second part is -ane. These prefixes form the basis for the names of most of the compounds that we will be naming during this course. Keep in mind that all ten of these compounds have C and H single bonds only.

Practice

Try naming the compounds shown here (they are also in exercise 9 of your workbook), before continuing. The answers are shown below.

CH3CH3

CH3CH2CH2CH2CH3

CH3(CH2)6CH3

Answers

CH3CH3

ethane

CH3CH2CH2CH2CH3

pentane
CH3(CH2)6CH3 octane

 

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E-mail instructor: Eden Francis

Clackamas Community College
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