Reactions Of Alkenes

Question 1

Why are alkenes more reactive than alkanes?

Answer 1

1. Due to the C=C bond
   —> pi bond breaks but sigma bond remains intact so can partake in addition reactions

Question 2

What happens during the addition of hydrogen to an alkene?

Answer 2

• passed over a Ni catalyst at 150 degrees
• hydrogen adds across the double bond forming an alkane

Hydrogen + Alkene —> Alkane

Question 3

What happens during the addition of a halogen to an alkene?

Answer 3

• at room temperature
• the halogen adds across the double bond forming a di-substituted halogenoalkane

Alkene + Halogen —> Haloalkane

Question 4

What does the addition of bromine to an alkene show?

Answer 4

• colour change from orange to colourless to show unsaturation which proves the presence of the C=C bond

Question 5

What happens during the addition of a hydrogen halide to an alkene?

Answer 5

• at room temperature
• hydrogen halide bubbled into liquid alkene
• adds across the double bond to form a halogenoalkane

Alkene + Hydrogen Halide —> Haloalkane

Question 6

What happens during the addition of steam to an alkene?

Answer 6

• heated to a high temperature and pressure in the presence of a phosphoric acid catalyst

Alkene + Water (g) —> Alcohol

Question 7

What happens during addition to unsymmetrical alkenes?

Answer 7

• form a mixture of organic products
  Note:
• more of one organic product formed than the other