chapter 13

Question 1

what are alkenes?

Answer 1

unsaturated hydocarbons (contain double C=C bond)

Question 2

what is the general formula for alkenes?

Answer 2

CnH2n

Question 3

what are Pi bonds caused by?

Answer 3

sideways overlap of P-orbitals above and below the sigma bond

Question 4

how do you draw before and after of a Pi bond?

Answer 4

two dumbbell shapes on the before
joined together on the after

Question 5

why are alkenes more reactive?

Answer 5

weaker Pi bond

Question 6

what is stereoisomerism?

Answer 6

same structural formula
different arrangement of atoms in 3D space

Question 7

E/Z isomerism only occur in compounds with…?

Answer 7

a C=C double bond
two different groups attached to it

Question 8

how do you tell between E and Z isomerism?

Answer 8

Z zee zame zide!!!!!
high priority

Question 9

what is an elimination reaction?

Answer 9

a small molecule is removed from a larger molecule

Question 10

what are some reactions of alkenes?

Answer 10

hydrogenation
halogenation
addition polymerisation
hydration

Question 11

what do double bonds in alkenes create?

Answer 11

high electron density region
due to presence of Pi electrons

Question 12

what does a high density of Pi electrons do?

Answer 12

attracts electrophiles

Question 13

what are electrophiles?

Answer 13

atom/group of atoms attracted to an electron rich centre and accepts an electron pair
usually positive ion/molecule

Question 14

what do you do to show the electrophilic addition mechanism first stage?

Answer 14

add charges to small molecule/ion (positive is closest to the double bond and is an electrophile)
curly arrow from double bond to electrophile
curly arrow from single bond to the negative part of the molecule

Question 15

what do you do to show the electrophilic addition mechanism second stage?

Answer 15

draw carbocation intermediate (contains positively charged carbon)
draw a + next to one carbon
draw a lone pair of electrons on the single molecule and a negative sign
draw a curly arrow from the lone pairs to the positve carbon

Question 16

what is Markownikoff’s rule?

Answer 16

major products form via the most stable carbocation intermediate
(primary, secondary, tertiary carbocation)

Question 17

how do carbocations increase stability?

Answer 17

more alkyl groups attached to positive carbon atom the more stable the carbocation

Question 18

what happens during addition polymerisation?

Answer 18

unsaturated alkenes undergo addition polymerisation to form long saturated polymer chains

Question 19

what are the risks of polymers?

Answer 19

non-biodegradable due to lack of reactivity

Question 20

what are the solutions to the risks of polymers?

Answer 20

recycling (stop plastic going to landfills, costly, mixed polymers are useless)
fuel (produce heat, generate steam, power turbines to produce electricity)

Question 21

what is the difference between biodegradable polymers and photodegradable polymers?

Answer 21

biodegradable broken down by bacteria in water, CO2, biological compounds
photodegradable broken down by absorbing light

Question 22

what must a compound have to be a cis-trans isomer?

Answer 22

C=C double bond
two different groups attached to each carbon double bond
one of the attached groups on each carbon atom has to be the same

Question 23

what is trans-isomerism?

Answer 23

trans - across the double bond

Question 24

what is cis-isomerism?

Answer 24

cis - same side of the double bond