alkenes

Question 1

Define alkenes

Answer 1

Unsaturated hydrocarbons that contain at least a C=C bond are made up of a pi bond and a sigma bond

Question 2

What is the general formula of alkenes

Answer 2

CnH2n

Question 3

How is a pi bond formed

Answer 3

Electrons in the adjacent p orbitals overlap above and below the carbon atoms, they can only be made after a sigma bond is formed

Question 4

What bond restricts the rotation of carbon atoms

Answer 4

pi bond

Question 5

What is the angle and shape of a double bond

Answer 5

Trigonal planar

120

Question 6

Are they more or less reactive than alkanes? Why?

Answer 6

More reactive due to the high electron density of double bond and the fact the pi-bond is slightly easier to break

Question 7

What intermolecular forces of attraction do alkenes have?

Answer 7

Only London forces due to non-polar bonds

Question 8

Are they soluble in water? Why?

Answer 8

No, non-polar bonds

Question 9

What are the types of isomers that can be formed using alkenes?

Answer 9

E/Z isomers - due to the restricted rotation

Cis-trans - if two of the same substituents are attached to each carbon

Question 10

What is an electrophile

Answer 10

Species that are electron pair acceptors

Question 11

What is the most stable type of carbonation intermediate? Why?

Answer 11

Alkyl groups have a positive inductive effect, so the most stable carbonation is the one bonded to the most other carbon atoms

Question 12

Major products will be formed from which kinds of carbocations

Answer 12

Tertiary (or most stable available)

Question 13

What conditions are needed for the electrophilic addition of H2O to an alkene? What is the type of reaction called?

Answer 13

Steam in the presence of acid catalyst - phosphoric acid

The reaction is called hydration

Question 14

What are the products of an alkenes hydration reaction

Answer 14

An alcohol

Question 15

What are the conditions needed for the electrophilic addition of a hydrogen halide to an alkene

Answer 15

Hydrogen halide gases must be at room temperature

Question 16

What is the reaction called when a halogen is added to alkene?

Answer 16

Halogenation

Question 17

How does a molecule with a non-polar bond react as if its an electrophile?

Answer 17

C=C double bond with a high electron density induces a temporary dipole in the halogen molecule

Question 18

How can an alkene be converted into alkane? What is the reaction called and what are the required conditions?

Answer 18

Alkene + hydrogen = alkane
hydrogenation
conditions: 150C, nickel catalyst

Question 19

What is an additional polymer

Answer 19

Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule

Question 20

What are monomers? What form do they usually take?

Answer 20

Molecules which combine to form a polymer

Usually have a C=C bond which breaks to leave a repeating pattern

Question 21

What are the ways in which plastics can be disposed of?

Answer 21

1. Landfill
2. Combustion
3. Electricity generation
4. Reuse
5. Recycle
6. Organic feedstock

Question 22

What are the disadvantages of recycling

Answer 22

1. Plastic must be sorted into different types
2. Expensive
3. Labour intensive
4. Requires high technology

Question 23

How do photodegradable polymers break down

Answer 23

They are broken down chemically using energy with wavelengths similar to light

Question 24

Explain what happens in organic feedstock

Answer 24

Plastics are separated and broken down into small organic molecules through a series of reactions, the molecules can be used to produce plastic and in other industries

Question 25

Give a disadvantage of photodegradable polymer

Answer 25

May not be exposed to sufficient light