module 4: alkenes

Question 1

functional group

Answer 1

C=C

Question 2

geometric isomer

Answer 2

same molecular and structural formula, different spatial arrangement of atoms

Question 3

E/Z isomerism condition

Answer 3

each carbon atom in C=C bond has two different functional groups attached

Question 4

pi bond

Answer 4

double bonds
sideways overlap of adjacent p orbitals above and below the plane
restricted rotation

Question 5

E

Answer 5

substituent groups on opposite sides of double bond

diagonal, Z shape

Question 6

Z

Answer 6

substituent groups on same side of double bond

Question 7

CIP

Answer 7

functional group on each carbon assigned a priority based on atomic number

note: if two atoms have same atomic number, the adjacent atoms with highest atomic number are taken into account

Question 8

cis/trans special case

Answer 8

both carbon atoms have the same functional groups

two of the substituent groups must be H

Question 9

preparation of alkenes via steam/ thermal cracking

Answer 9

high temperature and pressure
produces a high alkene yield

Question 10

preparation of alkenes via catalytic cracking

Answer 10

Al2O3 catalyst + pressure
heterogeneous
aromatic hydrocarbons produced

Question 11

forming alkenes: dehydration of alcohols

Answer 11

heated under reflux
concentrated H3PO4
producing alkene + water

Question 12

reactions: hydrolysis

Answer 12

300° C 60 atm
H2O/H3PO4
forming alcohol (consider 1° or 2°)

Question 13

reactions: hydrogen halides

Answer 13

haloalkane
(major/minor)

Question 14

reactions: bromination

Answer 14

dibromoalkane

Question 15

reactions: hydrogenation

Answer 15

Ni catalyst 150°C
alkane formed

Question 16

reactions: HBr(g)

Answer 16

bromoalkane
(major/minor)

Question 17

electrophilic addition

Answer 17

hard to describe
if you see this card, draw out mechanism for reaction between HBr and ethene
check

Question 18

Markownikoff’s rule

Answer 18

predicts outcome of electrophilic addition
halogen ends up bonded to most substituted C atom (smaller C, greater H)
most electronegative halogen bonds to most substituted carbon atom
favours production of major product

Question 19

comparison of stability of products formed

Answer 19

3°>2°>1°
tertiary products are the most stable

inductive properties push e- towards electron deficient carbocation and stabilise the molecule

Question 20

thermosetting polymers

Answer 20

do not soften on heating
linked by covalent bonds

Question 21

thermosoftening polymers

Answer 21

soften when heated, can be reshaped
intermolecular forces, no cross linking

Question 22

addition polymerisation conditions

Answer 22

high temperature + pressure
presence of a catalyst

Question 23

copolymerisation

Answer 23

2 or more different monomer units

Question 24

addition polymerisation

Answer 24

n monomer -> (repeating unit) n
double bond opens up/ becomes saturated