Everything Science Grade 12

1.7 CHAPTER 1. ORGANICMOLECULES

2. CH 3 CHCHCH 3

3.

H C

H

C C

H

C

H

H

H

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(1.) 01ns (2.) 01nt (3.) 01nu

The properties of the alkenes ESCQ

The properties of the alkenes are very similar to those of the alkanes,except that the
alkenes are more reactive because they are unsaturated. As with thealkanes, com-
pounds that have four or less carbon atoms are gases at room temperature, while those
with five or more carbonatoms are liquids.

Reactions of the alkenes ESCR

Alkenes can undergo addition reactions because they are unsaturated. They readily
react with hydrogen, water and the halogens. The double bond is brokenand a single,
saturated bond is formed. A new group is thenadded to one or both of the carbon
atoms that previously made up the double bond. The following are some examples:

1. Hydrogenation reactions

A catalyst such as platinum is normally neededfor these reactions

H 2 C = CH 2 + H 2 → H 3 C− CH 3 (figure 1.16)