2. Alkanes, alkanes and polymers

Question 1

What is a alkane.

Answer 1

Hydrocarbon with no double bond. Saturated.

Question 2

What is a alkene

Answer 2

Hydrocarbon with a double bond. unSaturated.

Question 3

Explain the halogenation of the alkanes.

Answer 3

Alakanes react with haolgens in UV (or 300deg) to produce Halogenoalkane and Hydrogen halide. This is a radical substitution. Cov bonds broken by homolytic fusion to make halogen radicals. A H atom gets substituted by this. Then the H and Br react.

Question 4

Mechanism for the chlorination.

Answer 4

• initiation: C₂—>2Cl* with UV by homolytic fision.
• Propagation 1: CH₄+Cl* —> *CH₃+HCL (could gets di,tri etc here)
• Propagation 2:*CH₃+Cl₂–> CH₃Cl +Cl* (and here)
• Terminations: any of the previus radicals combiing

Question 5

How is the pi bond formed.

Answer 5

above and below the the plane of the cabon atoms by sideways/latteral overlap of p-orbitals. Each carbon atom contributes 1 e- from the P orbital.

Question 6

ractivity of alkanes v alkenes

Answer 6

alkenes are more reactive, becuase the double bond becuase the pi bond is weaker then the sigma bond and this is what breaks.

Question 7

Addidition oif hydrogen to a alkene

Answer 7

Alkene+hydrogen–>alkane.

Nickle catalyst, 150 deg , high pressure.

Question 8

test for a double bond.

Answer 8

add bromine water. If a double bond is present it will decolourise, as the Br has reacted.

Question 9

Why would you get different products with a alke unsymmetric alkene + HBr(or other thing) substitution reaction.

Answer 9

If the original alkene isit makes two different products in the substitution

Question 10

Alkene + steam.

Answer 10

becomes a alcohol

H3PO4 catalyst, high temp and pressure.

Question 11

Alkene + halogen halide.

Answer 11

The delta + on the hydrogen is attracted to the E- dense region around thedouble bond.

A carbon cation, and a halide ion form as the double bond has bonded with the H and the Hhalide has heterolytically fissioned.

The Halide ion then bondes the the + carbon atom.

Question 12

Alkane + diatomic halide.

Answer 12

The Halide gets an induced dipole thanks to the e- rich region.

The double bond breaks and form with one Halide, the other becomes a halide ion by heterolytic fision. (forming a carbocation)

The halide ion then bonde with the +ve carbon.

Question 13

What are unstaurated compounds used for?

Answer 13

Make polymers (plastics)

Make margarine

Question 14

What is etene used for?

Answer 14

The chloretene used as a paint remover

The dialcohol is used as antifreeze,or in polyesters.

etanoic acid is vinegar.

Question 15

How do you make margerine?

Answer 15

Hydrogenation of unsaturated molecules.

This means that it partly solidifies and hardens which efeects the spreadabilty.

NICKEL CATALYST

Question 16

BP of ene v ane.

Answer 16

very similar but the alkene is a bit lower as vanderwaals are lower.

Question 17

Polymer reaction?9radical)

Answer 17

Via radical polymerisation. (200 deg, high pressure) . The radical breaks the double bond (and bonds)wich creates a radical monomer this contiues to break more , and join with them, creating a variety of polymer lengths and branchings.

Question 18

polymer reaction (ziegler natta)

Answer 18

us ea ziegler natta catalysr. The alkane gets passed over the catalyst, continually, at abolut 60 deg, produces unbranched polymers.

Question 19

Uses of polymer waster?

Answer 19

as a fuel source- for heat to be turne d into electricity.

In feedstock recycling- converting into Hydrogen and carmon monokide to be used to make more useful stuff.

Reforming the plastic

Question 20

How are PVC’;s recycled.

Answer 20

dissolved in a solution (to stop Cl going into the atmosphere), then precipitated out.

Question 21

what are biodegradable and compostable polymers.

Answer 21

When disposed they will be broken down naturally by the envionment to carbon dioxide and water, inorganic compounds, and biomass.