Alkenes and polymers

Question 1

What are Alkenes

Answer 1

Unsaturated hydrocarbons
Double c=c bond

Question 2

Alkene general formula

Answer 2

CnH2n

Question 3

What is a hydrocarbon

Answer 3

Molecule made of carbon and hydrogen atoms only

Question 4

E-Z isomerism occurs in alkenes due to ….

Answer 4

Restricted rotation around c=c
(Double bond)

Question 5

Explain CIP priority rules

Answer 5

Look going vertically look for priority group (w highest atomic number) on each side
Then going horizontally if priority group on same side ( Z isomer) if on different side (E isomer)

Question 6

Test for Alkenes

Answer 6

Adding alkene to bromine water makes it turn from orange to colourless.

Question 7

The arrangement of bonds around the C=C bond is _____ and the bond angle is around ______

Answer 7

Planar
120-121 degrees

Question 8

What bonds does C=C bond consist of

Answer 8

One sigma bond
One pi bond

Question 9

Define steroisomerism

Answer 9

Same structural formula different arrangement of atoms in space

Question 10

How does pi bond form

Answer 10

Sideways overlap of p orbitals

Question 11

What part of double bond is stronger sigma or pi bonds

Answer 11

Sigma bonds are stronger

Question 12

Physical properties of Alkenss

Answer 12

No sig difference in alkenes and alkanes based on mp and bp
Only vdw forces present
Both insoluble in water (cannot form h bonds w it)
Non polar

Question 13

Combustion of alkenes

Answer 13

Prod co2 and H2O
Not typically used as fuels instead used in chemical reactions

Question 14

Equation for test for Alkenes using Ethene

Answer 14

Ethene + bromine —> 1.2 di bromo ethane

Question 15

How does reactivity of alkenes differ from thag of alkasnes

Answer 15

Although c=c bond has lower bond Enthalpy it’s more reactive due to double bind creating an area of high electron density
Thus susceptible from attack by an electrophille

Question 16

Define electrophille

Answer 16

Electron pair acceptor
It’s an electron deficient species thag attacks and is attracted to areas of high electron density
They add across double bond bc it’s unsaturated

Question 17

What reaction mechanism do alkenes undergo

Answer 17

Electrophilic addition

Question 18

Talk though electrophillic addition

Answer 18

Occurs due to heterolutic fission
Non polar br2 approches c=c one br atom gets delta pos charge and other gets delta negative
Arrow from doube bind to delta positive br then from middle of thag bonf to delta neg br cus it takes binfing pair of e
Forms one new c - br and carbon cation
Then arrow from lone pair on br to carbon cation on alkane (double bond broken) then making haloalkane

Question 19

Explain why there’s an attraction between C=C and Br2 (3)

Answer 19

C=C is an area of high electron density
Br2 becomes polarised/induced dipole
Delta postive br attracted to C=C

Question 20

3 common electrophilles

Answer 20

Br2
Hbr (hydrogen bromide)
H2SO4 (sulphuric acid)
And reaction w steam

Question 21

The order of stability for carbocations is

Answer 21

tertirary
secondary
primary

Question 22

when unsymetrical alkene undergoes addition what products form

Answer 22

major and minor product

Question 22

what is a carbocation

Answer 22

an ion with positivly charged carbon atom

Question 23

There are two types of polymerisation…

Answer 23

addititon
condensation

Question 24

monomers in addition polymeristion

Answer 24

alkenes
c=c double bond

Question 25

Poly(alkenes) are chemically inert/unreactive bc

Answer 25

due to the strong C-C and C-H
bonds and non-polar nature of the bond and threfore non biodegrsdble

Question 26

how to draw repeating unit

Answer 26

single c-c bond
extend the bonds on either side of the c-c bond past the brackets surronding
n to the right

Question 27

if your asked to draw one rep unit wh\t do you do diff

Answer 27

you dont write an n to the right
n rep a large number of rep unit but your only drawing one

Question 28

why is polychloroethene stronger then polyethene

Answer 28

polyethene only has vdw but pvc has cl so can from stromger perm dipole dipole interactions so thus pvc more stronger and rigid

Question 29

whats pvc used for

Answer 29

windows
pipes

Question 30

what makes polymers like pvc more flexible

Answer 30

adding a plasticiser

Question 31

how do plasticers work

Answer 31

weaken imfs as mol small enough to get in between polymer chains forcing them apart so they can slide over eachother

Question 32

Markownikkoff’s rule states that the…

Answer 32

the major product will have the hydrogen in the hydrogen halide bond to the carbon atom already bonded to the highest number of hydrogens.

Question 33

polymers non biodegradable bc

Answer 33

strong c-c bonds

Question 34

polymers are non biodegrdable so how do we despose of them

Answer 34

burned as fuels
put in landfill
used as chemical feedstock

Question 35

Where is n on the monomer

Answer 35

On the left

Question 36

The more stable a carbocation the more …

Answer 36

Alkyl groups it’s joined to

Question 37

How many alkyl groups in primary secondary and tertiary carbocation

Answer 37

Primary - 1
Secondary - 2
Tertiary - 3

Question 38

What is the monomer for polyphenylethene

Answer 38

Phenylethene

Question 39

Are polyalkene chains saturated or unsaturated and why

Answer 39

Saturated with c-c single bonds

Question 40

What is stronger longer or shorter polymer chains

Answer 40

Longer
Bc the chains can get closer together and thus stronger vdw
Also higher number of electrons

Question 41

What’s plasticised pvc used for

Answer 41

Electrical cable insulation