13.1- HALOGENOALKANES- INTRODUCTION

Question 1

Do many halogenoalkanes occur naturally?

Answer 1

no

Question 2

What are halogenoalkanes the basis of?

Answer 2

many synthetic compounds

Question 3

Examples of halogenoalkanes being used as the basis for synthetic compounds? (4)

Answer 3

PVC
Teflon
anaesthetics
solvents

Question 4

What is PVC used to make?

Answer 4

drainpipes

Question 5

What is Teflon used for?

Answer 5

non-stick coating on pans

Question 6

What do halogenoalkanes have the skeleton of but with what attached?

Answer 6

alkane skeleton with one/ more halogen atoms in place of hydrogen atoms

Question 7

What is the general formula of halogenoalkanes?

Answer 7

CnH2n+1X

Question 8

What tells us in the names if a halogen in present?

Answer 8

the prefixes e.g. fluoro-, chloro-, bromo-, and iodo-

Question 9

What are numbers used for when naming halogenoalkanes?

Answer 9

to show on which carbon the halogen is bonded

Question 10

What do the prefixes di-, tri-, tetra- and so on show when naming halogenoalkanes?

Answer 10

how many atoms of each halogen is present

Question 11

When different halogens are present how is the halogenoalkane named?

Answer 11

listed in alphabetical order

Question 12

What sort of bond do halogenoalkanes have?

Answer 12

C-X bond

Question 13

As halogenoalkanes have a C-X bond, what does this mean?

Answer 13

bond is polar

Question 14

Why do halogenoalkanes have a polar bond?

Answer 14

halogens are more electronegative than carbon

Question 15

How does polarity change going down the halogen group?

Answer 15

bonds get less polar

Question 16

Can halogenoalkanes dissolve in water?

Answer 16

no

Question 17

Why can’t halogenoalkanes dissolve in water?

Answer 17

polar bonds are not polar enough

Question 18

What are the main intermolecular forces of attraction in halogenoalkanes?

Answer 18

dipole-dipole attractions and van der Waal forces

Question 19

What do halogenoalkanes mix with?

Answer 19

hydrocarbons

Question 20

As halogenoalkanes mix with hydrocarbons, what can they be used as?

Answer 20

used as dry-cleaning fluids and to remove oily stains

Question 21

What is oil a mixture of?

Answer 21

mixture of hydrocarbons

Question 22

What does the boiling point of a halogenoalkane depend on?

Answer 22

depends on number of carbon atoms and halogen atoms

Question 23

Two factors that affect boiling point of halogenoalkanes?

Answer 23

boiling point increases with increased chain length

boiling point increases going down halogen group

Question 24

What is both the effects of increased boiling point of halogenoalkanes caused by?

Answer 24

increased van der Waals forces as larger the molecule, greater the number of electrons

Question 25

What will increased branching in halogenoalkanes do to the boiling point?

Answer 25

lower the boiling point

Question 26

What is the boiling point of halogenoalkanes like compared to alkanes with similar chain lengths?

Answer 26

halogenoalkanes have higher boiling points

Question 27

Why do halogenoalkanes have higher boiling points than alkanes with similar chain lengths? (2)

Answer 27

as they have higher relative molecular masses and they're more polar

Question 28

Almost always which bond in halogenoalkanes break when they react?

Answer 28

C-X bond

Question 29

What two factors determine how readily the C-X bond reacts

Answer 29

bond polarity | bond enthalpy

Question 30

Why is the C-X bond polar

Answer 30

halogens more electronegative than carbon

Question 31

As the C-X bond in halogenoalkanes is polar, what does this mean for the carbon bonded to the halogen?

Answer 31

has a partial positive charge- electron deficient

Question 32

What can happen as the carbon bonded to the halogen in halogenoalkanes is electron deficient?

Answer 32

can be attacked by reagents that are electron rich or have electron-rich areas

Question 33

What are reagents that are electron rich or have electron-rich areas called?

Answer 33

nucleophiles

Question 34

What is a nucleophile?

Answer 34

electron pair donor

Question 35

What would the polarity of the C-X bond in halogenoalkanes predict?

Answer 35

the C-F bond would be the most reactive

Question 36

Why would the C-X bond predict the C-F bond would be the most reactive?

Answer 36

it's the most polar, so the C has the most positive charge so most easily attacked by a nucleophile

Question 37

What would the argument about C-X bond polarity predict for C-I?

Answer 37

C-I bond would be least reactive as it's the least polar

Question 38

How does the C-X bond change going down the group? (strength)

Answer 38

bonds get weaker

Question 39

What is the size of the fluorine atom like compared to the other halogens?

Answer 39

fluorine is the smallest atom

Question 40

How attracted are the shared electrons in the C-F bond?

Answer 40

the shared electrons in the C-F bond are strongly attracted to the fluorine nucleus

Question 41

How does the shared electrons in the C-F bond being strongly attracted to the fluorine nucleus affect the strength of the bond?

Answer 41

makes a strong bond

Question 42

Going down the group, how does the position of the electrons in the C-X bond change?

Answer 42

shared electrons in the C-X bond get further and further away from the halogen nucleus

Question 43

As the shared electrons in the C-X bond get further away what happens to the strength of the bond?

Answer 43

bond becomes weaker

Question 44

What would the bond enthalpies predict would be the most reactive compounds from the halogen group?

Answer 44

iodo-compounds as they have the weakest bonds

Question 45

What would the bond enthalpies predict would be the least reactive compounds from the halogen group?

Answer 45

fluoro-compounds as it has the strongest bonds

Question 46

What does experiments confirm about reactivity going down the halogen group?

Answer 46

reactivity increases going down the group

Question 47

As experiments confirm that reactivity increases going down the halogen group, what does this show?

Answer 47

bond enthalpy is a more important factor than bond polarity