Alkenes

Question 1

What are alkenes?

Answer 1

Unsaturated hydrocarbons

Question 2

What is the general formula of an alkene?

Answer 2

General formula is CnH2n

Question 3

What is the arrangement of bonds around the

>C=C [2]:

Answer 3

• Planar

- has the bond angle 120

Question 4

When do E-Z sterioisomers occur? [2]:

Answer 4

When…

• There is restricted rotation around the C=C double bond.
• There are two different groups/atoms attached both ends of the double bond.

Question 5

Why do E-Z isomers exist?

Answer 5

due to restricted rotation about the C=C bond

Question 6

When do you label an alkene a z-isomer?

Answer 6

If the priority atom is on the same side of the
double bond it is labelled Z
(The Zame Zide!)

Question 7

When do you label an alkene a E-isomer?

Answer 7

If the priority atom is on the opposite side of the double bond
(The Epposite side!)

Question 8

Reaction of Bromine with Alkenes:

Answer 8

alkene → dihalogenoalkane

Question 9

What is the reagent for the reaction of Bromine with Alkenes?

Answer 9

Bromine

Question 10

What are the conditions for the reaction of Bromine with Alkenes?

Answer 10

Room temperature (not in UV light)

Question 11

What is the mechanism for the reaction of Bromine with Alkenes?

Answer 11

Electrophilic Addition

Question 12

Reaction of Hydrogen Bromide with Alkenes:

Answer 12

alkene → halogenoalkane

Question 13

What is the reagent for the reaction of Hydrogen Bromide with Alkenes? [2]:

Answer 13

HCl or HBr

Question 14

What are the conditions for the reaction of Hydrogen Bromide with Alkenes?

Answer 14

Room temperature

Question 15

What is the mechanism for the reaction of Hydrogen Bromide with Alkenes?

Answer 15

Electrophilic addition

Question 16

What is the order of stability for carbocations?

Answer 16

tertiary > secondary >primary

Question 17

How is the major product formed in the electrophilic addition of alkenes?

Answer 17

the major product is formed via the more stable carbocation

Question 18

Reaction of Sulfuric acid with Alkenes stage 1:

Answer 18

alkene → alkyl hydrogensulfate

Question 19

What is the reagent for the reaction of Sulfuric acid with Alkenes stage 1?

Answer 19

concentrated H2SO4

Question 20

What are the conditions for the reaction of Sulfuric acid with Alkenes stage 1?

Answer 20

room temperature

Question 21

What is the mechanism for the reaction of Sulfuric acid with Alkenes stage 1?

Answer 21

Electrophilic addition

Question 22

Reaction of Sulfuric acid with Alkenes stage 2:

Answer 22

alkyl hydrogensulfate → alcohol

Question 23

What is the reagent for the reaction of Sulfuric acid with Alkenes stage 2?

Answer 23

Water

Question 24

What are the conditions for the reaction of Sulfuric acid with Alkenes stage 2?

Answer 24

warm mixture

Question 25

What type of reaction is the reaction of Sulfuric acid with Alkenes stage 2?

Answer 25

Hydrolysis reaction

Question 26

How are alkenes industrially converted into water?

[2]:

Answer 26

• In one step rather than then two

- They are reacted with water in the presence of an acid catalyst

Question 27

What are the conditions for the industrial conversion of alkenes into alcohols? [3]:

Answer 27

• High temperature 300 to 600°C
• High pressure 70 atm
• Catalyst of concentrated H3PO4

Question 28

Testing for Alkenes with Bromine water [2]:

Answer 28

• Bromine water decolourises in the presence of a double bond
• turn brown bromine water colourless

Question 29

What are addition polymers formed from?

Answer 29

Alkenes in addition polymerisation

Question 30

Why are polyalkenes unreactive?

Answer 30

Poly(alkenes) like alkanes are unreactive due to the strong C-C and C-H bonds

Question 31

How do you determine a high priority atom?

Answer 31

The atom with the highest number has the highest priority