What do these have in common?

II. Hydrocarbons – organic compounds that containonly atoms of hydrogen and carbon.

As the number of carbons in a hydrocarbon increases, its boiling point (bp) increases. This is because bigger molecules attract each other with greater dipole-dipoleforces. This holds them together better in a liquid and makes it harder to break them apartinto gases.

bp = -162 0C bp = -89 0C bp = 36 0C

H C

A. The alkanes are a homologous series of saturated (only single bonds) hydrocarbons that release energy when burned.

1. methane CH4

2. ethane C2H6

3. propane C3H8

4. butane C4H4

5. ETC.

Each next heavier member of the alkanes is formed by adding a CH2 unit. See

Ex. ethane + CH2 unit propane

General formula for alkanes: CnH2n+2 (see Table Q)

n = 1: CnH2n+2 = C1H2•1+2 = C1H4 = CH4 methane

n = 2: CnH2n+2 = C2H2•2+2 = C2H6 ethane

n = 3: CnH2n+2 = C3H2•3+2 = C3H8 propane

n = 4: CnH2n+2 = C4H2•4+2 = C4H10 butane

H

H

C

Compounds in which each member differs from the one before it by the same additional unit are called a homologous series.

Ex. What is the molecular formula for the alkane that has 8 carbon atoms?alkane formula: CnH2n+2

n = 8: CnH2n+2 = C8H2•8+2 = C8H18

Sketch its structural formula:

Ball and stick view:

Skeletal view:

Note how the actual shaped is bent or kinked.

Use Table P to name them. Each alkane is named by adding the prefix to –ane.

Ex. What is the name of the alkane of the last example?

Ex. What is the name of thealkane that has five C atoms?

What is its molecular formula?

Sketch its structural formula.

octane

pentane

C5H12

B. The alkenes are a homologous series of unsaturated (not all single bonds) hydrocarbons that contain one double bond.

There must be at least 2 carbon atoms to form an alkene. The simplest member isethene (also known as ethylene and olefin).

ethene: structuralformula:

Other views:

C2H4

Many ethylenes = polyethylenePolyethylene or polythene (IUPAC name polyethene or poly(methylene)) is the most widely used plastic, with an annual production of approximately 80 million metric tons.[1] Its primary use is within packaging (plastic bag, etc.).

HDPE is used in products and packaging such as milk jugs, detergent bottles, margarine tubs, garbage containers and water pipes. One third of all toys are manufactured from HDPE. In 2007 the global HDPE consumption reached a volume of more than 30 million tons.[6

Next alkene after ethene:

Other views:

molecular formula:

structural formula:

C3H6

propene

How many carbon atoms does it have?

How many double bonds?

3

1

The next alkenes are: butene, pentene, etc.Alkenes are named using the same prefixes that are used for alkanes.

The general formula for alkenes is in Table Q:

CnH2n

Ex. What are the name and general formula for the alkene that has nine carbon atoms?

C9H18

C. The alkynes are a homologous series of unsaturated (not all single bonds) hydrocarbons that contain one triple bond.

As with the alkenes, there must be at least 2 carbon atoms to form an alkyne. The simplest member is ethyne (also known as acetylene):

molecular formula:

structural formula:

Other views:

C2H2

Next alkyne after ethyne:

Other views:

molecular formula:

structural formula:

C3H4

propyne

How many C atoms does it have?

How many double bonds?

3

1

The next alkynes are: butyne, pentyne, etc.Alkenes are named using the same prefixes that are used for alkanes and alkenes.

The general formula for alkenes is in Table Q:

CnH2n-2

Ex. What are the name and general formula for the alkyne that has seven carbon atoms?

heptyne

Ex. Name and give the molecular formula of the…

…alkane with 6 carbon atoms:

…alkene with 10 carbon atoms:

…alkyne with 5 carbon atoms:

Ex. Circle all alkanes, star all alkenes and box all

alkynes in the list below. (Some are not possible.)CH4 C3H8 C2H2

C5H10 CH2 C3H8

C4H10 C6H10 C7H12

C20H42 C3H6 C9H20

C3H10 C2H4 C8H14

hexane

decene

pentyne

double

double +2

double - 2

Ex. Name and give the molecular formula of the…

…alkane with 6 carbon atoms:

…alkene with 10 carbon atoms:

…alkyne with 7 carbon atoms:

Ex. Circle all alkanes, star all alkenes and box all

alkynes in the list below. (Some are not possible.)

Mark with an S for saturated and a U for unsaturated.CH4 C3H8 C2H2

C5H10 CH2 C3H8

C4H10 C6H10 C7H12

C20H42 C3H6 C9H20

C3H10 C2H4 C8H14

hexane

decene

heptyne

S

S

S

S

S

S

U U

U

U

U

U

U

U

Ex. Put in order of increasing boiling points

from left to right:decane, ethane, nonane, pentane,

Ex. What are the names of the following?

1.

2.

3.

butyne

heptane

hexene

ethane, pentane, nonane, decane

What is this ring of hydrocarbons, which isproduced in volcanoes,forest fires and cigarettesmoke…?

Very useful,very toxic.

D. The examples so far are open hydrocarbons.

Other types include cyclic hydrocarbons. Two

examples of these are shown here:

_______ hexane a _________ “ring”

structural skeletal structural skeletal

Are the above two compounds alkanes, alkenes or alkynes?

cyclobenzene

cyclohexane is an alkane

benzene is in a class by itself