Halogenoalkanes Flashcards

1
Q

what does halogenoalkanes contain ?

A

saturated hydrocarbon chains with a carbon atom bonded to a halogen atom ( F, CI, Br or I )

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2
Q

what bonds do halogenoalkanes contain ? why ?

A

polar bonds since the halogens are more electronegative than a carbon atom
- electron density is drawn towards the halogen, forming delta positive and negative regions

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3
Q

how do we make halogenoalkanes ?
ethane + chlorine - >

A

chloroethane + HCI
condition: UV

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4
Q

how do we make halogenoalkanes ?
ethene + hydrogen bromide - >

A

bromoethane

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5
Q

physical properties of halogenoalkanes

A

they have a higher boiling point than their analogous alkane because the polarity of the carbon - halogen bond leads to stronger intermolecular forces
- there are more electrons so London forces are stronger

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6
Q

why are halogen carbon bonds polar ?

A

due to the greater electronegativity of the halogen atom this leads to a much stronger pd- pd interaction

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7
Q

as alkyl chain length increases what happens to the solubility ?

A

it decreases

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8
Q

is halogenoalkanes more/ less soluble compared to analogous alkanes ?

A

more because more similar intermolecular forces with the solvent means greater solubility

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9
Q

what forces makes halogenoalkanes more soluble in water than alkanes

A

PD - PD forces - must form hydrogen bonds

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10
Q

what is an elimination ?

A

a reaction which produces an unsaturated product by loss of atoms or groups

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11
Q

what is a base ?

A

a chemical species with a pair of electrons to remove a hydrogen ion

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12
Q

how are halogenoalkanes usually attacked by ?

A

nucleophiles

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13
Q

what is hydrolysis ?

A

a reaction in which a compound is split apart in a reaction with water

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14
Q

what solution is a good test for the presence of halogenoalkanes ?

A

aqueous silver nitrate

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15
Q

what does AgCI make ?

A

white

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16
Q

what does AgBr make ?

A

cream

17
Q

what does AgI make ?

A

yellow

18
Q

in silver chloride, what does the precipitate do in both ammonia (aq) and conc. ammonia ?

A
  • ppt dissolves
  • ppt dissolves
19
Q

in silver bromide, what does the precipitate do in both ammonia (aq) and conc. ammonia ?

A
  • ppt remains
  • ppt dissolves
20
Q

in silver idoide, what does the precipitate do in both ammonia (aq) and conc. ammonia ?

A
  • ppt remains
  • ppt remains
21
Q

testing for haloalkanes

A

C2H5X (ethanol) + H2O (l) -> C2H5OH (aq) + AgX (s)

22
Q

comparing the halogen atoms - order them from slowest to fastest

A

fluorine, chlorine, bromine and iodine

23
Q

during nucleophilic substitution what bond must break ?

A

C - halogen bond

24
Q

how does the rate of hydrolysis become faster ?

A

the weaker the bond the less energy required to break it

25
Q

why is ethanol used in the testing of halogenoalkanes ?

A

solvent
- both haloalkanes and water dissolve in ethanol

26
Q

Reactant: aqueous potassium hydroxide
formula of attacking species/ nucleophile or base:
conditions:
products:

A

formula of attacking species/ nucleophile or base: :OH- nucleophile
conditions: warm and aqueous
products: alcohol + halide ion

27
Q

Reactant: aqueous silver nitrate in ethanol
formula of attacking species/ nucleophile or base:
conditions:
products:

A

formula of attacking species/ nucleophile or base: :OH2 nucleophile
conditions: warm, acidified silver nitrate
products: alcohol and silver halide precipitate

28
Q

Reactant: potassium cyanide
formula of attacking species/ nucleophile or base:
conditions:
products:

A

formula of attacking species/ nucleophile or base: :CN- nucleophile
conditions: heated under reflux in ethanol
products: nitrile and halide ion

29
Q

Reactant: concentrated ammonia
formula of attacking species/ nucleophile or base:
conditions:
products:

A

formula of attacking species/ nucleophile or base: :NH3 nucleophile and then base
conditions: ethanol, heat, pressure and sealed tube
products: amine or ammonium salt

30
Q

Reactant: ethanolic potassium hydroxide
formula of attacking species/ nucleophile or base:
conditions:
products:

A

formula of attacking species/ nucleophile or base: :OH- base
conditions: heat and ethanol
products: alkene, water and halide ion