haloalkane

Question 1

what is an essential condition for free radial substitution and what does it do

Answer 1

· UV light

· Provides the energy required to break the halogen-halogen bond and start the reaction

Question 2

The definition for a free radical is:

Answer 2

A species with an unpaired electron

Question 3

describe what happens in initiation

Answer 3

· The halogen molecule splits into two free-radicals

· Breaking the halogen-halogen bond is called homolytic fission

Question 4

describe what happens in propagation 1

Answer 4

The free-radical produced during initiation takes a H from the alkane

This turns the alkane into a free-radical and also produces a hydrogen halide

Question 5

describe what happens in propagation 2

Answer 5

carbon radical removes chlorine and forms a haloalkane
2nd chlorine left as a radical

Question 6

what happens in termination

Answer 6

· Two free-radicals combine to make a molecule

Question 7

what is a disadvantage of producing haloalkanes through free radical substitution

Answer 7

a wide range of products can form as a result of further substitution steps

Question 8

To reduce the amount of further substitution you would

Answer 8

Use excess alkane

Question 9

state the overall equation for a free radical substitution reaction

Answer 9

halogen + alkane → haloalkane + hydrogen halide

Question 10

Write an overall equation for the formation of trichloromethane by the reaction of chloromethane with chlorine

Answer 10

CH3Cl + 2Cl2 → CHCl3 + 2HCl

Question 11

what does ozone (O3) do

Answer 11

absorbs sun’s harmful UV rays

Question 12

what is the overall equation for the decomposition of ozone

Answer 12

2 O3 →3 O2

Question 13

why are CFC’s harmful

Answer 13

they release chlorine radicals which break down ozone

Question 14

give the initiation equation for ozone breakdown

Answer 14

CCl3F → Cl* + *CCl2F

Question 15

give the equation for propagation 1 for ozone breakdown

Answer 15

Cl* + O3 ⟶ ClO* + O2

Question 16

give the equation for propagation 2 for ozone breakdown

Answer 16

ClO* + O3 ⟶ 2O2 + Cl

Question 17

CFCs were so damaging to the ozone layer, as the breakdown of ozone can be caused by a single chlorine free-radical. This is because

Answer 17

Cl● catalyzes the decomposition of ozone as it is not used up in the reaction. It is a catalyst

Question 18

Definition – Nucleophile

Answer 18

An electron-pair donor

Question 19

what are the reagent conditions and products formed from nucleophilic substitution of OH- ions

Answer 19

· Reagent: NaOH or KOH

· Conditions: Aqueous solvent

· Type of product: Alcohol

Question 20

what are the reagent conditions and products formed from nucleophilic substitution of CN- ions

Answer 20

· Reagent: KCN

· Conditions: Water and ethanol solvent

· Type of product: nitrile

Question 21

what are the reagent conditions and products formed from nucleophilic substitution of NH3- ions

Answer 21

· Reagent: Excess NH3

· Conditions: Ethanol solvent, heat, and pressure

· Type of product: Amine

Question 22

what it is called when haloalkanes are split using water and how can it occcur

Answer 22

hydrolysis, haloalkanes are insoluble in water

Question 23

how long it takes for precipitate to form of AgCl

Answer 23

very long

Question 24

how long it takes for precipitate to form of AgBr

Answer 24

long

Question 25

how long it takes for precipitate to form of AgI

Answer 25

really fast

Question 26

when experimenting rates of substitution why do you use ethanol

Answer 26

it acts as a a solvent

Question 27

why is hydrolysis slower in different haloalkanes

Answer 27

because more energy is needed to break the C- halogen bond

Question 27

what is the method for rates of substitution (hydrolysis)

Answer 27

1. Place a measured sample of each halogenoalkane, (equal molar amounts), into separate test tubes and place in to a water bath at 50oC 2. Into another test tube place a solution of ethanol, water and aqueous silver nitrate and place in the same water bath. 3. Once at equal temperature add equal volumes of the ethanol mixture and haloalkane solutions together. 4. Time how long it takes for each precipitate to form

Question 28

what are the reagent conditions and products formed from elimination of an haloalkane

Answer 28

· Reagent: NaOH or KOH · Conditions: Hot & Ethanolic solvent · Type of product: Alkene

Question 29

In the elimination reaction for a haloalkane what do OH- ions act as

Answer 29

a base (electron acceptor)