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Organic Chemistry > Alkanes/Haloalkanes > Flashcards

Alkanes/Haloalkanes Flashcards

1
Q

Define Ozone

A

O3 in atmosphere - absorbs UV

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2
Q

Outline the danger of Holes in the Ozone

A

O3 decrease = increase UV & skin cancer

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3
Q

Define CFCs and outline their impact on Ozone

A

Chlorofluorocarbons - decrease in O3

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4
Q

Outline the 2 reactions of how CFCs reduce Ozone

A
  1. Cl* + O3 -> ClO* + O2
  2. ClO* + O3 -> Cl* + 2O2
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5
Q

Outline the overall reaction of CFC Ozone reduction

A

203 -> 3O2

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6
Q

Why is alkane combustion important?

A

Hi energy release

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7
Q

Outline Complete combustion

A

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

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8
Q

Outline incomplete combustion

A

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

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9
Q

Outline the purpose of Catalytic converters

A

Removes CO & NOx (toxic)

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10
Q

Outline the process inside a catalytic converter

A

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

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11
Q

Outline the danger of S impurities

A

H in H2O in atmosphere = H2SO4

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12
Q

What’s used in Flue Gas Desulfurisation?

A

CaO + gypsum

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13
Q

Identify the importance of Flue Gas Desulfurisation?

A

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

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14
Q

Define Cracking

A

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

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15
Q

Outline the conditions and products of Thermal Cracking

A

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

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16
Q

Outline the Conditions and Products of Catalytic Cracking

A

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

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17
Q

Define Chlorination of Alkanes

A

Alkanes + Halogens ->(UV)-> Halogenoalkanes

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18
Q

Outline how Alkane Chlorination works

A

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

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19
Q

Outline the Initiation in Chlorination (define and reaction)

A

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

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20
Q

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

A

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

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21
Q

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

A

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

22
Q

Define Fractional Distillation

A

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

23
Q

Outline the 3 steps of Fractional Distillation

A
  1. Crude Oil vaporised
  2. Vapours rise, cool, condensed
  3. Proucts siphoned off
24
Q

Outline how the hydrocarbons are separated when vapourised

A

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

25
Q

Define Haloalkane

A

Alkane bonded to Halogen atom(s)

26
Q

Define Nucleophile

A

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

27
Q

Define Electrophile

A

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

28
Q

Define Electronegativity

A

Ability 4 atom to attract e- in covalent bond

29
Q

Outline the 3 types of Haloalkane

A

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

30
Q

Outline the 3 physical properties of Haloalkanes

A
  1. C Chain increase=boiling point + VDW forces increase
  2. Down group 7 = boiling point increase
  3. If < room temp state is (g)
31
Q

Outline the 3 factors affecting haloalkane boiling point

A
  1. C chain length (more VDW)
  2. Type of Halogen (more e-=stronger VDW)
  3. Primary, Secondary or Tertiary
32
Q

Outline why there are permanent dipole forces in Haloalkanes

A

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

33
Q

Outline the outlier to Haloalkane permanent dipoles

A

Iodine (so big)

34
Q

Why don’t permanent dipoles impact the boiling points?

A

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

35
Q

Outline the 3 types of Haloalkanes

A

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

36
Q

Outline the trend in BP for the type of Haloalkane

A

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

37
Q

Why are Haloalkanes only slightly soluble in water?

A

Must break VDWs & H bonds between H2O molecules

38
Q

What does the reactivity of Haloalkanes depend on?

A

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

39
Q

Define Nucleophilic substitution

A

Nucleophile replaces a group/atom in OG Molecule

40
Q

Describe the general mechanism for Haloalkane Nucleophilic Substitution

A

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

41
Q

Outline the nucleophilic substitution of Haloalkanes with Hyrdoxide Ions

A

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

42
Q

Describe the mechanism for Nucleophilic Substitution of Haloalkanes with Hydroxide Ions

A

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

43
Q

Outline the nucleophilic substitution of Haloalkanes with Cyanide Ions

A

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

44
Q

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

A

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

45
Q

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

A

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

46
Q

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

A

Same as Hydroxide ions

47
Q

Outline the conditions of the nucleophilic substitution of ammonia and alkanes

A

Ethanolic ammonia in a sealed tube - primary amine formed

48
Q

Outline the steps of the nucleophilic substitution of ammonia and alkanes

A
  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
49
Q

Outline the conditions for the elimination of Haloalkanes

A
  1. NaOH/KOH as a base
  2. No H2O present ethanol needed as a solvent
  3. Heat needed
50
Q

Describe the mechanism of the elimination reaction of Haloalkanes

A
  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
51
Q

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

A

Primary = Nucleophilic Substitution
Secondary = Both
Tertiary = Elimination

Organic Chemistry (3 decks)

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