13.2- NUCLEOPHILIC SUBSTITUTION IN HALOGENOALKANES

Question 1

In how many steps do most reactions of organic compounds take place?

Answer 1

via a series of steps

Question 2

How can you predict the steps that most organic compound reactions take?

Answer 2

by thinking about how electrons are likely to move

Question 3

What can looking at how electrons are likely to move in organic compound reactions help you understand?

Answer 3

understand why reactions take place as they do

Question 4

What are nucleophiles- what do they do?

Answer 4

reagents that attack + form bonds with positively or partially positively charged carbon atoms

Question 5

What charge does a nucleophile have?

Answer 5

negatively charged or has an atom with a slightly negative charge

Question 6

What does a nucleophile have? (electrons)

Answer 6

lone pair of electrons

Question 7

What can a nucleophile use its lone pair of electrons to do?

Answer 7

form a covalent bond

Question 8

On a nucleophile where is the lone pair situated?

Answer 8

situated on an electronegative atom

Question 9

So in organic chemistry what is a nucleophile?

Answer 9

species that has a lone pair of electrons with which it can form a bond by donating its electrons to an electron deficient carbon atom

Question 10

What are some common nucleophiles? (3)

Answer 10

hydroxide ion, -:OH
ammonia, :NH3
cyanide ion, -:CN

Question 11

What will nucleophiles do to the halogen in halogenoalkanes?

Answer 11

replace the halogen in a halogenoalkane

Question 12

What is the reaction called when a nucleophile replaces the halogen in a halogenoalkane?

Answer 12

nucleophilic substitution

Question 13

What does a reaction mechanism describe?

Answer 13

route from reactants to products via a series of theoretical steps

Question 14

What may reaction mechanisms involve?

Answer 14

short-lived intermediates

Question 15

What are curly arrows used to show?

Answer 15

show how electron pairs move in organic reactions

Question 16

Where is the lone pair of electrons of a nucleophile attracted towards?

Answer 16

positively charged carbon atom

Question 17

What is the halide ion originally from the halogenoalkane called?

Answer 17

leaving group

Question 18

What does the rate of substitution with the halogenoalkane depend on?

Answer 18

the halogen

Question 19

Why are fluoro-compounds unreactive?

Answer 19

due to strength of the C-F bond

Question 20

How does the rate of reaction change going down the halogen group and why?

Answer 20

rate of reaction increases as the C-X bond strength decreases

Question 21

At what condition does the reaction between a halogenoalkane and hydroxide ion occur very slowly?

Answer 21

room temperature

Question 22

What is done to speed up the reaction between a halogenoalkane and hydroxide ion?

Answer 22

warm the mixture

Question 23

Do halogenoalkanes mix well with water?

Answer 23

no

Question 24

As halogenoalkanes don’t mix well with water, what is added during the reaction with halogenoalkanes and hydroxide ions?

Answer 24

ethanol used as solvent in which halogenoalkane and aqueous sodium ( or potassium) hydroxide both mix

Question 25

What is the reaction between the halogenoalkane and hydroxide ion known as?

Answer 25

hydrolysis reaction

Question 26

What happens when halogenoalkanes are warmed with an aqueous alcoholic solution of potassium cyanide?

Answer 26

nitrile formed

Question 27

What does a nitrile have an extra of in comparison to the starting halogenoalkane?

Answer 27

one extra carbon in the chain than the starting halogenoalkane

Question 28

What is the nitrile formed having one extra carbon than the starting halogenoalkane useful for?

Answer 28

useful if you want to make a product that has one carbon more than the starting material

Question 29

Under what condition is a reaction of halogenoalkanes with an excess concentrated solution of ammonia in ethanol happen?

Answer 29

under pressure

Question 30

What does a reaction of halogenoalkanes with an excess concentrated solution of ammonia in ethanol produce?

Answer 30

amine, RNH2

Question 31

Why is ammonia a nucleophile? (2)

Answer 31

it has a lone pair of electrons that it can donate

nitrogen atom has a slightly negative charge

Question 32

What is the charge of the ammonia nucleophile?

Answer 32

neutral

Question 33

As the ammonia nucleophile is neutral what must be lost to form the neutral product, amine?

Answer 33

a proton, H+ must be lost

Question 34

What happens to the H+ which is lost when amine is to be produced in a reaction between a halogenoalkane and ammonia nucleophile?

Answer 34

H+ ion reacts with a second ammonia molecule to form an NH4+ ion

Question 35

Why are nucleophilic substitution reactions useful?

Answer 35

they’re a way of introducing new functional groups into organic compounds

Question 36

What can halogenoalkanes be converted into due to nucleophilic reactions? (3)

Answer 36

alcohols
amines
nitriles

Question 37

Order of what halogenoalkane can be turned into after primary amine?

Answer 37

halogenoalkane -> primary amine -> secondary amine -> tertiary amine

Question 38

Order of what halogenoalkane can be turned into after alcohol?

Answer 38

halogenoalkane -> alcohol -> aldehyde -> carboxylic acid

Question 39

Order of what halogenoalkane can be turned into after nitrile?

Answer 39

halogenoalkane -> nitrile -> primary amine OR carboxylic acid