Everything Science Grade 12

1.7 CHAPTER 1. ORGANICMOLECULES

More practice video solutions or help at http://www.everythingscience.co.za

(1.) 01nm (2.) 01nn (3.) 01np (4.) 01nq (5.) 01nr

The alkenes ESCO

In the alkenes, there isat least one double bond between two carbonatoms. This
means that they are unsaturated and are more reactive than the alkanes. The simplest
alkene is ethene (also known as ethylene), whichis shown in figure 1.14.

(a) C C

H

H

H

H

(b) CH 2 CH 2 (c) C 2 H 4

Figure 1.14: The (a) structural, (b) condensedstructural and (c) molecular structure
representations of ethene

As with the alkanes, thealkenes also form a homologous series. They have the gen-
eral formula CnH 2 n. The second alkene inthe series would therefore be C 3 H 6. This
molecule is known as propene (figure 1.15). Note that if an alkene has two double
bonds, it is called a diene and if it has three double bonds it is called a triene.

(a) H C C C

H

H

H H

H

(b) CH 3 CHCH 2 (c) C 3 H 6

Figure 1.15: The (a) structural, (b) condensedstructural and (c) molecular structure
representations of propene

The alkenes have a variety of uses. Ethylene for example is a hormonein plants that
stimulates the ripeningof fruits and the opening of flowers. Propene is an important
compound in the petrochemicals industry. It is used as a monomer to make polypropy-
lene and is also used asa fuel gas for other industrial processes.