Download Simple Organic Compounds: Alkanes Objective Organic Chemistry

Simple Organic Compounds: Alkanes
Objective
lesson 1
chapter 14/15
You will be able to draw, name and list properties
of single bonded carbon and hydrogen
compounds.
Organic Chemistry
It is the study of molecular carbon compounds.
It does not include carbonates (CO32-), cyanides (CN-),
carbon dioxide, or carbon monoxide.
The variety of bonds that can be formed by carbon,
make it a very versatile element.
· Four bonding electrons
· Multiple bonds with itself and other elements
· Many forms including chains, spheres, tubes, and rings.
Functional Groups
Special arrangement of atoms that are mainly
responsible for the chemical and physical behavior of a
molecule.
Examples are –OH for alcohols and –COOH for acids.
see p. 565 for a list.
Example
3-methylpent-2-ene
Hydrocarbon chains are named according to the
number of carbons in the chain.
The first four have prefixes that are different
from those learned for molecular compounds.
Meth examples -CH4
Eth
-C2H6
Prop
-C H
3 8
-C4H10
But
The remaining have prefixes the same at those
learned for molecular compounds.
See page 546 of the textbook.
You must memorize this list of prefixes.
Alkanes
This is the simplest of the organic compound families.
They are chains of carbon atoms connected by single
bonds.
The remaining bonding electrons are connected to
hydrogen atoms.
Since all of the bonding electrons are occupied and
single, these are called saturated compounds.
Use prefixes shown on page 546 of text, adding -ane.
Example:
i)
1 carbon has prefix meth. Since this is an
alkane we add the ending -ane to
obtain methane.
ii) 4 carbons have prefix but. Thus it becomes
butane.
Write the names and draw the structure for C7 H16 and
C 3H 8
General Formula
The general formula for an alkane is CnH2n+2.
Example:
i) pentane has 5 carbon atoms, so n=5 and the formula
becomes:
C5H2(5) + 2 or C5H12
Write the formulae for octane and hexane.
Rules to be followed
1: Identify the longest continuous chain to form the root
of the name.
Example:
2:Identify the branched groups.
The prefixes are the same as those for alkanes except they end
with -yl.
ie. CH3 - methyl group
CH2 - CH3 - ethyl group
3: Identify the position of the groups.
This is done by counting the carbons in the root chain. Begin
labeling the carbons from the end nearest a branch group.
Example:
4: If more than one branch is present then name them
in alphabetical order.
Examples
If more than one of a single branch group is present
then identify each location and add a prefix of di- or trito indicate the numbers of each group.
Example
Example
Write the structural formula for 3–ethylheptane and 2,2dimethylpropane.
Physical Properties
(see p. 551)
# of
carbons
Boiling
point
State and uses
1-4
Less than
30˚C
Gases: fuels
5-16
30-275˚C
liquids: fuels,
plastics
16-22
Greater
than
250˚C
Heavy liquids:
lubricants
18 and over
Greater
than
400˚C
Waxy solids:
greases and
paraffin waxes
26 or more
Greater
than
500˚C
Solids: asphalts
and tars
Assignment
Read text p. 538-551
Do practice problems 1-9
For a review of chemistry 20
concepts in chemical bonding read
p. 532-535 in textbook.