Crude Oil (3): Alkanes and the hydrocarbon code

Cracking the Hydrocarbon Code:

In this post I'm hoping to help you know how to build the formulas of the one type of hydrocarbon called an alkane: cracking the hydrocarbon code.

There are three parts to the hydrocarbon code:

Part 1:  The prefix of the hydrocarbon name:

The prefix of the hydrocarbon name tells you how many carbon atoms are in the molecule of the hydrocarbon so:

Part 2: The suffix of the hydrocarbon name:

The suffix of the hydrocarbon name tells you the type of hydrocarbon.

There are three basic types according to the type of bond between the carbon atoms.

-ane:              only single bonds between all atoms

-ene:              one double bond between two carbon atoms: the rest single bonds

-yne:              one triple bond between two carbon atoms: the rest single bonds

This table shows you the simplest examples of the alkanes and the alkenes.  

You ought to work out how the displayed formulas of the alkynes would look.  

To help you here are the first three names and formulas: ethyne C2H2, Propyne C3H4, and Butyne C4H6.  

For those who want to check how you did, you can find some answers scrolling down this page here. 

Lastly, here is a table of the first ten alkanes with there boiling points:

Here is task you can do: try plotting number of carbon atoms against boiling point and seeing what the chart looks like and then see if you can predict from your chart the boiling point of a hydrocarbon with eleven carbon atoms.

You'll find an answer here.

The explanation for your chart takes us back to the first post on oil fractionation.

Fractional distillation happens because all the different parts of crude oil have different boiling points.

The different fractions have different boiling points because they contain particles (hydrocarbon molecules) with different structures.

The structures contain just two key elements-carbon (C) and hydrogen (H) hence hydrocarbon.

The more carbon atoms the higher the boiling point.

Here are the trends we can observe in the fractions from crude oil:

low boiling point     <-------------------------------------> high boiling point
small hydrocarbons <-------------------------------------> large hydrocarbon
low density              <------------------------------------------> high density
runny and thin         <------------------------------------------> viscous and dense
weak intermolecular forces <-------------------------------------> high intermolecular forces
lighter colour          <------------------------------------------> darker colour

distill from higher                                                          distil from lower
on the column        <------------------------------------------>  down the column

Pages on the "Mole" and "Using the Mole" in chemical calculations are here