halogenoalkanes

Question 1

general formula halogenoalkanes

Answer 1

CnH2n+1Hal

Question 2

functional group

Answer 2

C-Hal

Question 3

what does the presence of the polar bond in halogenoalkanes mean

Answer 3

they’re more reactive than alkanes

Question 4

3 uses of halogenoalkanes

Answer 4

• refrigerants
• solvents
• pharmaceuticals

Question 5

how are halogenoalkanes named

Answer 5

after the parent alkane with the prefix chloro, bromo, iodo etc.

Question 6

what must be indicated if there are more than 3 carbon atoms in the molecule

Answer 6

the position of the halogen

Question 7

what must be indicated if 2 or more halogens are present

Answer 7

their positions in the chain

Question 8

how are the halogens named if there are 2 of them in the chain and they are different

Answer 8

in alphabetical order

Question 9

what 2 reactions do halogenoalkanes take part in

Answer 9

nucleophilic substitution and elimination

Question 10

what is the halogen atom replaced with in a nucleophilic substitution reaction

Answer 10

by a new group of atoms

Question 11

nucleophile

Answer 11

electron pair donor

Question 12

why do halogenoalkanes take part in nucleophilic substitution

Answer 12

the carbon is bonded to a halogen and so it is rendered electron deficient

Question 13

where does the nucleophile donate its pair of electrons to in nucleophilic substitution

Answer 13

the delta plus c atom to form a new bond

Question 14

how does the C-Hal bond break in nucleophilic substitution and what does it form

Answer 14

Heterolytic fission

halide ion formed

Question 15

examples of common nucleophiles

Answer 15

hydroxide
cyanide
ammonia

Question 16

what do halogenoalkanes react with aqueous hydroxides to form

Answer 16

alcohols

Question 17

what is the reaction between halogenoalkanes and aqueous hydroxides often referred to as

Answer 17

hydrolysis

Question 18

hydrolysis

Answer 18

the breaking of a bond using water

Question 19

what is the reagent in nucleophilic substitution with aqueous hydroxides

Answer 19

the hydroxide

Question 20

what conditions are needed for nucleophilic substitution using hydroxide

Answer 20

warm and aqueous

Question 21

general equation for the nucleophilic substitution between halogenoalkane and hydroxide

Answer 21

R-Hal + NaOH > R-OH + NaHal

Question 22

reagent for nucleophilic substitution between halogenoalkane and cyanide

Answer 22

cyanide ion

Question 23

conditions for nucleophilic substitution between halogenoalkane and cyanide

Answer 23

warm and ethanolic

Question 24

general equation for for nucleophilic substitution between halogenoalkane (bromo) and (potassium) cyanide

Answer 24

RBr + KCN > RCN + KBr

Question 25

what does reacting a halogenoalkane with cyanide increase

Answer 25

the length of the carbon chain

Question 26

what do halogenoalkanes react with excess ammonia to form

Answer 26

amines

Question 27

reagent for nucleophilic substitution between halogenoalkane and ammonia

Answer 27

NH3

Question 28

conditions for nucleophilic substitution between halogenoalkane and ammonia

Answer 28

ethanolic and warm

Question 29

general equation for nucleophilic substitution between halogenoalkane and ammonia

Answer 29

R-Hal + 2NH3 > RNH2 + NH4 + Hal-

Question 30

what does the rate of substitution reactions of halogenoalkanes depend on

Answer 30

the c-hal bond enthalpy

Question 31

what does a halogenoalkane react to form in an elimination reaction

Answer 31

an alkene

Question 32

elimination

Answer 32

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

Question 33

reagent for elimination reaction with halogenoalkanes

Answer 33

hydroxide

Question 34

conditions for elimination reaction with halogenoalkanes

Answer 34

HOT and ethanolic

Question 35

sequence of events in elimination reactions with halogenoalkanes

Answer 35

- halogen atom always removed - H atom from an adjacent C atom also removed - double bond forms between the two C atoms

Question 36

what is the role of the hydroxide in elimination with halogenoalkanes

Answer 36

base

Question 37

substitution vs elimination using hydroxide: conditions

Answer 37

s: warm and aqueous e: hot in ethanol

Question 38

substitution vs elimination using hydroxide: major product

Answer 38

s: alcohol e: alkene

Question 39

substitution vs elimination using hydroxide: role of OH-

Answer 39

s: nucleophile e: base

Question 40

what properties of chloroflourocarbons make them suitable for use as solvents and refrigerants

Answer 40

non-toxic and low reactivity

Question 41

what did the properties of chloroflourocarbons lead to

Answer 41

the depletion of the ozone layer

Question 42

where does ozone form

Answer 42

in the upper atmosphere

Question 43

how does ozone form

Answer 43

from the reaction of oxygen atoms with oxygen molecules

Question 44

equation for formation of ozone:

Answer 44

O + O2 > O3

Question 45

why is the ozone layer beneficial

Answer 45

it absorbs UV radiation that can cause skin cancer

Question 46

what did scientists discover that waste CFCs didnt do

Answer 46

break down easily and so would rise up to the upper atmosphere and break down to form chlorine radicals

Question 47

what do chlorine radicals do and what has this led to

Answer 47

catalyse the breakdown of ozone led to a hole in the ozone layer

Question 48

equation for chlorine radicals reacting with ozone

Answer 48

O3 + Cl. > O2 + ClO. ClO+ O3> 2O2 + Cl.

Question 49

what alternatives to CFCs are now used

Answer 49

organohalogens that don't contain chlorine