halogenalkanes and mechanisms

Question 1

what is homolytic fission

Answer 1

homolytic fission happens when each one of the atom in the bond gets one electron

Question 2

what is heterolytic fission

Answer 2

heterolytic fission occurs when one atom in the bond gets both electrons

Question 3

what does a one headed arrow show

Answer 3

the movement on one electron

Question 4

what does a double headed arrow show

Answer 4

the movement of two electrons

Question 5

what is a free radical

Answer 5

a free radical is a reactive species which posses an unpaired electron they do not have a charge and are shown by a dot to the right of the atom

Question 6

what does it mean if you classify a halogenoalkanes as primary

Answer 6

a primary halogenoalkane will have two hydrogens bonded to the carbon with the halogen on it

Question 7

what does it mean if you can classify a halogenoalkane and secondary

Answer 7

a secondary halogenoalkane will have one hydrogen bonded to the carbon with the halogen on it

Question 8

what does it mean if you can classify a halogenoalkane and tertiary

Answer 8

a tertiary halogenoalkane will have no hydrogens bonded to the carbon with the halogen on it

Question 9

what are the two mechanisms that can occur to halogen alkanes

Answer 9

nucleophilic substitution or elimination

Question 10

what is nucleophilic substitution

Answer 10

in this type of reaction the halogen atom is replaced with a new group of atoms

Question 11

what is a nucleophile

Answer 11

a nucleophile is a electron pair doner

Question 12

why does nucleophilic substitution occur to halogenoalkanes

Answer 12

because the carbon hydrogen bond is polar

Question 13

what are the three products of nucleophilic substitution of a halogenoalkane and what are there nucleophiles

Answer 13

1- alcohol = OH-
2-Amine = NH3
3- nitrile = C—N

Question 14

how can nucleophilic substitution occur

Answer 14

the carbon in the carbon halogen bon will be slightly positive due to the difference in electronegativity and since the nucleophiles is very negative due loan pair it will attack the carbon atom.
but since carbon cant be bonded to more then four atoms the electrons in the covalent bond will homiletically fission to the halogen creating a negative halogen ion and product depending on the nucleophile

Question 15

what effects the rate of nucleophilic substitutions reactions

Answer 15

the bond enthalpy which is the strength of the halogen carbon bond due to the difference in electronegativity. the weaker the bond the quicker the reaction so fluoride talked the longest and iodide the quickest

Question 16

what is hydrolysis

Answer 16

hydrolysis is defines as the splitting of a molecule ( in this case a halogenoalkane) with water

Question 17

how can we use hydrolysis to test which halogenoalkane has the fastest substitution reactions

Answer 17

through hydrolysis the quicker the precipitate formed the quicker the reaction

Question 18

what are the conditions for hydrolysis to test rate of reaction of a halogenoalkane

Answer 18

warmed to 60 degrees with aqueous silver nitrate using ethanol as a mutual solvent

Question 19

in nucleophilic substitution hydrolysis to test rate of reactions why do we use water as our nucleophile

Answer 19

water is a poor nucleophile but it can react slowly in with haloalkanes in nucleophilic substitution

Question 20

in nucleophilic substitution hydrolysis to test rate of reaction what colour does it go in the halogen in the haloalkane is chlorine

Answer 20

white- fastest

Question 21

in nucleophilic substitution hydrolysis to test rate of reactions what colour does it go in the halogen in the haloalkane is bromine

Answer 21

cream

Question 22

in nucleophilic substitution hydrolysis to test rate of reaction what colour does it go in the halogen in the haloalkane is iodine

Answer 22

yellow-slowest

Question 23

what is reagent of hydrolysis to make alcohol

Answer 23

sodium/ potassium hydroxide

Question 24

what are the condition needed for hydrolysis to make alcohols

Answer 24

warm aqueous

Question 25

what is the reagent for nucleophilic substitution haloalkane to nitrile

Answer 25

KCN dissolved in ethanol/water mixture

Question 26

what are the conditions for nucleophilic substitution of haloalkane to nitrile

Answer 26

heating under reflux

Question 27

what is the reagent for nucleophilic substitution of haloalkane to amine

Answer 27

excess ammonia NH3 dissolved in ethanol

Question 28

what are the conditions for nucleophilic substitution of haloalkane to amine

Answer 28

heating under pressure in a sealed tube

Question 29

why in the nucleophilic substitution reaction of haloalkane to amine do we use excess ammonia

Answer 29

to minimise the amount the haloalkanes and amine react as this reduces our amine yield

Question 30

what condition has to be applied to halogens to make then react with alkanes

Answer 30

UV light

Question 31

what is the reagent of free radical substitution

Answer 31

your halogen

Question 32

what type of fission occurs in free radical substitution

Answer 32

homolytic

Question 33

what are the steps of free radical substitution

Answer 33

1- initiation where UV light form halogen radicals 2-propigation 1where hydrogen bons with the halogen propagation 2 where radical on carbon and one atom in diatomic halogen bond 3-termination which is the removal of the radical

Question 34

what happen sin an emlimination reaction

Answer 34

the removal of small molecule from the organic molecule

Question 35

what is the reagent for an elimination reaction

Answer 35

sodium/potassium hydroxide

Question 36

the condition for elimination reaction

Answer 36

reflux and hot ethanoic acid which encourages elimination nstead fo neucleophilic subcitution

Question 37

what is the type of reagent for elimination reaction

Answer 37

base (H+ proton accepter)

Question 38

why are alkenes more reactive

Answer 38

alkenes are more reactive due to their high electron density in the double cc bond

Question 39

why do alkenes undergo addition reactions

Answer 39

to for a saturate molecule as a small molecule is added across the double cc bond

Question 40

what is the reagent for electrophile addition

Answer 40

halogen ( CL2 or BR20) which acts as our electrophiles

Question 41

what is a asymmetrical alkene

Answer 41

the groups attached to either side of the carbon carbon double bond aren't the same

Question 42

what is the products of electrophilic substitution of asymmetrical alkenes

Answer 42

majors or minor products

Question 43

what defines if a product of electrophile addition of asymmetrical alkenes will be major or minor

Answer 43

the major product is the one that is the most stable carbocation which is always the tertiary one and the least primary

Question 44

what are the uses of haloalkanes

Answer 44

halo alkanes can be used in things such as refrigerators, pesticides and aerosol propellants

Question 45

what have haloalkanes stopped being used in thigs such as refrigerators, pesticides and also aerosol propellants

Answer 45

many of these uses have stopped due to the toxicity of the haloalkanes and also their detrimental effect on the atmosphere

Question 46

what is the ozone layer and what are its benefits

Answer 46

O3 layer in the atmosphere that filters out much of the harmful sun UV radiation

Question 47

what happens if Ozone is in the lower atmosphere

Answer 47

it contributes the formation of smog as a pollutant

Question 48

why are chlorofluorocarbons in the atmosphere bad

Answer 48

they causes holes in the ozone layer as the UV light causes chlorine radicals to form due to the UV light. these chlorine radicals catalyse the decomposition of the ozone

Question 49

what are used instead of chlorofluorocarbons and why are they better

Answer 49

hydrofluorocarbons as the carbon fluoride bond is much stronger then a chloride carbon bond due to fluoride being the most electronegative