Ch13 Hydrocarbons- alkenes

Question 1

Unsaturated hydrocarbon

Answer 1

contain one or more double bonds

Question 2

Alkenes

Answer 2

unsaturated hydrocarbon that contain at least one C=C double bond

Question 3

Boiling point of alkenes

Answer 3

lower than alkanes as cannot pack together as tightly
- less surface contact so less London dispersion forces
- less energy to overcome

Question 4

Bonding in alkenes

Answer 4

C=C bond contains a sigma bond and pi bond

Question 5

sigma bond

Answer 5

single covalent bond made up of two shared electrons with the electron density concentrated between the two nuclei

Question 6

pi bond

Answer 6

Formed by sideways overlap of two p orbitals on adjacent carbon atoms, each providing one elevtron

Question 7

Bond angle of C=C

Answer 7

C-H bond on either side of double bond is 120°- trigonal planar

Question 8

stereoisomerism

Answer 8

compounds have the same molecular and structural formula but a different 3-dimensional spatial arrangement

• occurs because C=C prevents freedom of rotation otherwise pi bond will break

Question 9

E isomer

Answer 9

if the two attached atoms with the highest atomic numbers are on the diagonally opposite sides of the double bonds

Question 10

Z isomer

Answer 10

if the two attached atoms with the highest atomic numbers are NOT on the diagonally opposite sides of the double bonds

Question 11

Addition reactions

Answer 11

two molecules combine together to form a single products

CH2=CH2 + X-Y -> CH2XCH2Y

Question 12

hydrogenation

Answer 12

reagent- hydrogen
conditions- nickel catalyst at 150°C

Question 13

Bromination

Answer 13

reagent- bromine
conditions- mix at room temperature
observations- decolourisation of bromine

Question 14

Hydration

Answer 14

reagent- water(steam)
conditions- an acid catalyst at 300°C and high pressure

Question 15

Electrophile

Answer 15

An electron-pair acceptor(attracted to electron dense regions) that forms a covalent bond

Question 16

curly arrows

Answer 16

movement of electron pair
- from area that is electron rich to an area that is electron deficient

Question 17

heterolytic fission

Answer 17

process of breaking covalent bond where one atom takes both of the shared pair of electrons

Question 18

example process of electrophilic substitution

Answer 18

1. inital curly arrow starts at pi bond and points to Br+
2. Second curly arrow shows movement of bonded pair of electrons in Br-Br bond towards Br-, causing heterolytic fission of the molecule
3. an intermediate carbocation is formed with Br- ions
4. 3rd curly arrow from lone pair of electrons on Br- to positively charged carbocation shows formation of new organic molecule

Question 19

Markownikoff’s rule

Answer 19

the addent other than hydrogen goes to the least hydrogenated carbon atom

Question 20

Addition polymerisation

Answer 20

formation of long-chain molecule from linking up of monomer sub-units

Question 21

polymer waste

Answer 21

• landfill sites(non-biodegradable)
• incineration(release useful energy but can produce poisonous gases)
• feedstock for production of new polymers(have to be separated as mixture yield inferior plastic products)

Question 22

Biodegradable polymer aim

Answer 22

• contain active functional group that can be attacked by bacteria
• is sustainable and doesn’t use finite resources