Haloalkanes

Question 1

What happens when an alkane and a halogen are mixed in the dark?

Answer 1

Nothing

Question 2

What happens when an alkane and a halogen are mixed in sunlight?

Answer 2

An explosive reaction happens and haloalkane molecules are formed

Question 3

What is a free radical substitution reaction?

Answer 3

A chain reaction which takes place in 3 stages

Question 4

What are the three steps in free radical substitution and what happens in each step?

Answer 4

Initiation: Free radicals formed
Propagation: Radicals use and reformed in a chain reaction
Termination: Radicals removed

Question 5

What is a free radical?

Answer 5

An element/compound with an unpaired electron

Question 6

What is ozone?

Answer 6

An allotrope of oxygen

Question 7

How is ozone formed?

Answer 7

Its formation is a result of the interaction between oxygen and uv light. It is formed when an oxygen molecule forms a coordinate bond with an oxygen atom.

Question 8

How does ozone affect the levels of harmful uv radiation reaching the earths atmosphere?

Answer 8

It acts as a barrier, preventing too much from reaching the atmosphere.

Question 9

How can uv radiation be harmful to us?

Answer 9

High level of UV radiation damages DNA causing skin cancers.

Question 10

What are CFC’s?

Answer 10

CFC’s are compounds containing Chlorine, Fluorine and Carbon.

Question 11

What are CFC’s used as (3 things)?

Answer 11

Refrigerator coolants
Aerosol propellants
Dry cleaning solvents

Question 12

What provides the energy for the C-Cl bonds in CFC’s to break in the stratosphere?

Answer 12

UV light

Question 13

What is the overall reaction for the destruction of ozone?

Answer 13

2o3 –> 3O2

Question 14

What acts as a catalyst for ozone breakdown?

Answer 14

A chlorine radical

Question 15

How many ozone molecules can one chlorine radical destroy on average?

Answer 15

thousands

Question 16

In what year did the Montreal protocol come into affect (to decrease the use of CFC’s)

Answer 16

1989 (Tv)

Question 17

What compounds can be used as alternatives to CFC’s as they have similar properties?

Answer 17

hydrofluorocarbons

Question 18

What is the advantage of hydrofluorocarbons?

Answer 18

There is no chlorine in them so there is no chlorine radicals so there is no ozone depletion

Question 19

What is a nucleophile?

Answer 19

An electron npair donot

Question 20

What are 3 common nucleophiles?

Answer 20

The hydroxide ion, Cyanide ion and Ammonia

Question 21

What does a nucleophilic substitution entail?

Answer 21

It is a mechanism where an electron pair donor replaces another atom/ group of atoms in a reactions

Question 22

What type of Carbon - Halogen bond does a haloalkane contain?

Answer 22

Polar

Question 23

What is formed when a haloalkane is warmed with aqueous NaOH or KOH?

Answer 23

An alcohol is formed

Question 24

What is formed when haloalkanes are warmed with ethanolic Potassium (or Sodium) Cyanide?

Answer 24

Compounds called nitriles are formed

Question 25

What is formed when haloalkanes are warmed with an excess of concentrated ammonia?

Answer 25

Compounds called primary amines are formed.

Question 26

What is the typical way that haloalkanes react?

Answer 26

Nucleophilic substitution

Question 27

What is an elimination reaction?

Answer 27

An elimination reaction is one in which an atom/ group of atoms is removed from a reactant

Question 28

What does a haloalkane need to be mixed with in order for it to react by elimination?

Answer 28

Sodium (or potassium) hydroxide that has been dissolved in ethanol (not water) and heated.

Question 29

What does the hydroxide ion act as in an elimination reaction?

Answer 29

A base (H+ acceptor)

Question 30

What reaction conditions favours substitution and what conditions favour elimination?

Answer 30

Aqueous OH- ions and warm (substitution) Ethanolic OH- ions and hot (elimination)

Question 31

Which structures of haloalkanes favours substitution and which favours elimination

Answer 31

Primary (substitution) Secondary (both) Tertiary (elimination)

Question 32

When do you get isomeric products (haloalkanes)?

Answer 32

When the haloalkane from which HX is being eliminated is unsymmetrical (e.g E-Z isomers)