alkenes

Question 1

general formula of alkenes

Answer 1

CnH2n

Question 2

how do pi bonds form

Answer 2

sideways double overlap of 2p orbitals above and below the plane

Question 3

what is the shape of alkenes?

Answer 3

trigonal planar

Question 4

what is the bond angle of alkenes?

Answer 4

120

Question 5

stereoisomers definition

Answer 5

same structural formula but a different arrangement of the atoms in space

Question 6

what are the 2 types of stereoisomers

Answer 6

• E/Z isomerism

- optical isomerism

Question 7

explain how E/Z isomers occur

Answer 7

• restricted rotation around the double bond
• groups attached are fixed relative to each other
• rigid due to high electron density

Question 8

what are the conditions needed for E/Z isomerism

Answer 8

• C=C double bond

- different groups attached to each carbon atom of the double bond

Question 9

what is cis- trans isomerism

Answer 9

used to describe a special case of E/Z isomerism

Question 10

what are the conditions needed for cis- trans isomers?

Answer 10

• C=C double bond
• more than 2 different groups attached to each carbon atoms of the double bond
• one of the attached groups on each carbon must be a hydrogen

Question 11

what is a cis- isomer called in E/Z isomerism?

Answer 11

z

Question 12

what is a trans- isomer called in E/Z isomerism?

Answer 12

E

Question 13

how are groups prioritised in Cahn- Ingold- Prelog?

Answer 13

• priority bases on their atomic number

- the group with higher atomic number at the 1st point of difference has higher priority

Question 14

explain why alkenes are more reactive than alkanes

Answer 14

• pi bonds are more exposed than sigma electrons

- pi bonds readily break and alkenes undergo addition reactions easily

Question 15

electrophile definition

Answer 15

electron pair acceptor

Question 16

what is the characteristic mechanism for alkenes

Answer 16

electrophilic addition

Question 17

why is the tertiary carbocation more stable than the secondary and primary carbocation?

Answer 17

• each alkyl group donates and pushes electrons towards the positive charge of the carbocation
• the more alkyl groups attached to the positively charged carbon atom, the more the change is spread out, making it more stable

Question 18

how are carbocations classified

Answer 18

classified by the number of alkyl groups attached to the positively charged carbon atom

Question 19

what do feedstock recycling describe?

Answer 19

describes the chemical and thermal processes that can reclaim monomers, gases, or oil from waste polymers

Question 20

state 1 atmospheric pollutant caused by the burning of PVC

Answer 20

HCl(g)

Question 21

how are polymers suitable for storing food and chemical safety?

Answer 21

lack of reactivity

Question 22

what does recycling reduce?

Answer 22

reduces their environmental impact by conserving finite fossil fuels as decreasing the amount of waste going to landfill

Question 23

what are the advantages of bio plastics?

Answer 23

• protect our environment

- conserves valuable oil reserves

Question 24

what is the advantage of feedstock recycling?

Answer 24

able to handle unsorted and unwashed polymers

Question 25

what do bio plastics offer?

Answer 25

offer a renewable and sustainable alternative to oil- based products