4.23-4.28 Alkenes

What are alkenes?

Unsaturated hydrocarbons

What is the general formula of an alkene?

Cn H2n

What do all alkenes contain?

A double carbon bond

What is a functional group?

The atom or group of atoms responsible for the characteristic reactions of an organic compound

What is C2H4?

Ethene

What is C3H6?

Propene

What is C4H8?

But-1-ene

What is C5H10?

Pent-1-ene

What are the first four members of the alkene homologous series?

1. Ethene

2. Propene

3. But-1-ene

4. Pent-1-ene

Why can unsaturated compounds make more bonds with other atoms? (what do unsaturated compounds have and ? can be opened up to…)

Unsaturated compounds have a C=C double bond which can be opened up to allow incoming atoms to form another single bond with each C atom of the functional group

What do the numbers in butene, pentene and hexene refer to? (Use pent-2-ene as an example)

The carbon atom in which the C=C begins, counting from the left. In pent-2-ene, C5H10 has the C=C between the 2nd and 3rd carbon atoms

When does an addition reaction take place?

When two or more molecules combine to form a larger molecule with no other products

What is formed when bromine is reacted with an alkene? (Type it twice to remember the spelling).

A dibromoalkane. A dibromoalkane.

Fill in the gap! All alkanes are [ ] and all alkenes are [ ]

All alkanes are saturated and all alkenes are unsaturated

Why is bromine water used in the test for alkenes?

Bromine water is safer and easier to handle than bromine

How is bromine water used to test for alkenes?

1. Bromine water added to an alkene

2. Bromine atoms add across the C=C bond

3. Solution no longer contains free bromine so it loses it colour (no longer orange)

Why are alkenes more reactive than alkanes?

Alkenes are unsaturated: they have a C=C double bond