Alkanes/Haloalkanes Flashcards by Thomas McNamara

Define Ozone

O3 in atmosphere - absorbs UV

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Outline the danger of Holes in the Ozone

O3 decrease = increase UV & skin cancer

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Define CFCs and outline their impact on Ozone

Chlorofluorocarbons - decrease in O3

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Outline the 2 reactions of how CFCs reduce Ozone

Cl* + O3 -> ClO* + O2
ClO* + O3 -> Cl* + 2O2

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Outline the overall reaction of CFC Ozone reduction

203 -> 3O2

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Why is alkane combustion important?

Hi energy release

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Outline Complete combustion

(Enough O2 present) X + O2 -> CO2 + H2O

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Outline incomplete combustion

(Not enough O2) X+O2 -> CO+C+H2O

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Outline the purpose of Catalytic converters

Removes CO & NOx (toxic)

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Outline the process inside a catalytic converter

HC, CO, NOx (from air N2) + rhodium catalyst -> N2, H2O, CO2

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Outline the danger of S impurities

H in H2O in atmosphere = H2SO4

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What’s used in Flue Gas Desulfurisation?

CaO + gypsum

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Identify the importance of Flue Gas Desulfurisation?

Pollutants -> global warming, H+ rain, health issues

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Define Cracking

C-C-C-C-C-C -> C-C C-C C-C (more useful)

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Outline the conditions and products of Thermal Cracking

Conditions: 1200K & 7000 kPa
Products: Mixture of CnH2n+2 & CnH2n

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Outline the Conditions and Products of Catalytic Cracking

Conditions: 720K, Normal Pa, Zeolite catalyst
Products: Aromatic Compounds and C rings

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Define Chlorination of Alkanes

Alkanes + Halogens ->(UV)-> Halogenoalkanes

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Outline how Alkane Chlorination works

UV breaks down Halogen bonds -> Free Radicals & initiation, propagation & termination

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Outline the Initiation in Chlorination (define and reaction)

Halogen broken down
Cl2 ->(UV)-> 2Cl*

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Outline the 2 Propagation steps in Chlorination (define and both reactions)

H replaced and Cl* reformed as a catalyst
Cl* + CH4 -> *CH3 + HCl
CH3 + Cl2 -> CH3Cl + Cl

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Outline the Termination step of Chlorination (define and 3 reactions)

2 free radicals join to form stable product
CH3 + CH3 -> C2H6
OR
Cl + * CH3 ->CH3Cl
OR
Cl + Cl -> Cl2

Define Fractional Distillation

Process used to separate hydrocarbons of different lengths from crude oil through different boiling points

Outline the 3 steps of Fractional Distillation

Crude Oil vaporised
Vapours rise, cool, condensed
Proucts siphoned off

Outline how the hydrocarbons are separated when vapourised

Depends on boiling points
Long C Chain = condense low
Short C chain = condense high
Mushroom trays - collect can’t go back down

Define Haloalkane

Alkane bonded to Halogen atom(s)

Define Nucleophile

e- pair donor - attracted to areas of low e- density

Define Electrophile

e- pair acceptor - attracted to areas of hi e- density

Define Electronegativity

Ability 4 atom to attract e- in covalent bond

Outline the 3 types of Haloalkane

Primary = 2 or 3 H Secondary = 1 H Tertiary = No H

Outline the 3 physical properties of Haloalkanes

1. C Chain increase=boiling point + VDW forces increase 2. Down group 7 = boiling point increase 3. If < room temp state is (g)

Outline the 3 factors affecting haloalkane boiling point

1. C chain length (more VDW) 2. Type of Halogen (more e-=stronger VDW) 3. Primary, Secondary or Tertiary

Outline why there are permanent dipole forces in Haloalkanes

Electronegativity diff with C & Halogen C is + dipole Halogen is - dipole

Outline the outlier to Haloalkane permanent dipoles

Iodine (so big)

Why don't permanent dipoles impact the boiling points?

Due to increasing strength of VDW Forces the hi e- Number outweighs loss of permanent dipole

Outline the 3 types of Haloalkanes

Primary = 2/3 H Secondary = 1 H Tertiary = No H

Outline the trend in BP for the type of Haloalkane

Primary highest: Closer together -> stronger VDW = more energy to break

Why are Haloalkanes only slightly soluble in water?

Must break VDWs & H bonds between H2O molecules

What does the reactivity of Haloalkanes depend on?

Bond length: C-F < C-Cl < C-Br < C-I Bond strength: C-I < C-Br < C-Cl < C-F Molecule size: F < Cl < Br < I

Define Nucleophilic substitution

Nucleophile replaces a group/atom in OG Molecule

Describe the general mechanism for Haloalkane Nucleophilic Substitution

1.-ve Nucleophile attacks Chiral C 2. C has 5 bonds 1 bond breaks 3. Halogen removed, becomes -

Outline the nucleophilic substitution of Haloalkanes with Hyrdoxide Ions

Haloalkanes + OH- boiled under reflux + (aq) NaOH/(aq) KOH Forms alcohols

Describe the mechanism for Nucleophilic Substitution of Haloalkanes with Hydroxide Ions

OH- (nucleophile) attacks + dipole C from behind Halogen leaves - becomes Halide ion

Outline the nucleophilic substitution of Haloalkanes with Cyanide Ions

Haloalkanes + CN- boiled under reflux + (aq) ethanol Forms Nitriles

Outline the reaction for the nucleophilic substitution of Haloalkanes with Hydroxide ions.

R-X + OH- -> R-OH + X-

Outline the reaction for the nucleophilic substitution of Haloalkanes with Cyanide ions.

R-X + CN- -> R-CN + X-

Describe the mechanism for the nucleophilic substitution of Haloalkanes with Cyanide ions.

Same as Hydroxide ions

Outline the conditions of the nucleophilic substitution of ammonia and alkanes

Ethanolic ammonia in a sealed tube - primary amine formed

Outline the 4 steps of the nucleophilic substitution of ammonia and alkanes

1. e- pair on NH3 attacks + dipole C 2. NH3 must remove a H atom & Halide ion forms 3. H atom forms +NH4 with another NH3 molecule 4. +NH4 attracted to -Halide ion

Outline the 3 conditions for the elimination of Haloalkanes

1. NaOH/KOH as a base 2. No H2O present ethanol needed as a solvent 3. Heat needed

Describe the mechanism of the elimination reaction of Haloalkanes

1. :OH- attacks H atom on C adjacent to C atom with Halogen to form H2O 2. H breaks off forming a C=C - Halogen atom breaks off = Halide ion

Outline how the type of halogenoalkane determines either an elimination or nucleophilic substitution

Primary = Nucleophilic Substitution Secondary = Both Tertiary = Elimination