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haloalkane Flashcards

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1
Q

what is an essential condition for free radial substitution and what does it do

A

· UV light

· Provides the energy required to break the halogen-halogen bond and start the reaction

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2
Q

The definition for a free radical is:

A

A species with an unpaired electron

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3
Q

describe what happens in initiation

A

· The halogen molecule splits into two free-radicals

· Breaking the halogen-halogen bond is called homolytic fission

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4
Q

describe what happens in propagation 1

A

The free-radical produced during initiation takes a H from the alkane

This turns the alkane into a free-radical and also produces a hydrogen halide

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5
Q

describe what happens in propagation 2

A

carbon radical removes chlorine and forms a haloalkane
2nd chlorine left as a radical

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6
Q

what happens in termination

A

· Two free-radicals combine to make a molecule

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7
Q

what is a disadvantage of producing haloalkanes through free radical substitution

A

a wide range of products can form as a result of further substitution steps

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8
Q

To reduce the amount of further substitution you would

A

Use excess alkane

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9
Q

state the overall equation for a free radical substitution reaction

A

halogen + alkane → haloalkane + hydrogen halide

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10
Q

Write an overall equation for the formation of trichloromethane by the reaction of chloromethane with chlorine

A

CH3Cl + 2Cl2 → CHCl3 + 2HCl

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11
Q

what does ozone (O3) do

A

absorbs sun’s harmful UV rays

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12
Q

what is the overall equation for the decomposition of ozone

A

2 O3 →3 O2

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13
Q

why are CFC’s harmful

A

they release chlorine radicals which break down ozone

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14
Q

give the initiation equation for ozone breakdown

A

CCl3F → Cl* + *CCl2F

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15
Q

give the equation for propagation 1 for ozone breakdown

A

Cl* + O3 ⟶ ClO* + O2

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16
Q

give the equation for propagation 2 for ozone breakdown

A

ClO* + O3 ⟶ 2O2 + Cl

17
Q

CFCs were so damaging to the ozone layer, as the breakdown of ozone can be caused by a single chlorine free-radical. This is because

A

Cl● catalyzes the decomposition of ozone as it is not used up in the reaction. It is a catalyst

18
Q

Definition – Nucleophile

A

An electron-pair donor

19
Q

what are the reagent conditions and products formed from nucleophilic substitution of OH- ions

A

· Reagent: NaOH or KOH

· Conditions: Aqueous solvent

· Type of product: Alcohol

20
Q

what are the reagent conditions and products formed from nucleophilic substitution of CN- ions

A

· Reagent: KCN

· Conditions: Water and ethanol solvent

· Type of product: nitrile

21
Q

what are the reagent conditions and products formed from nucleophilic substitution of NH3- ions

A

· Reagent: Excess NH3

· Conditions: Ethanol solvent, heat, and pressure

· Type of product: Amine

22
Q

what it is called when haloalkanes are split using water and how can it occcur

A

hydrolysis, haloalkanes are insoluble in water

23
Q

how long it takes for precipitate to form of AgCl

A

very long

24
Q

how long it takes for precipitate to form of AgBr

A

long

25
Q

how long it takes for precipitate to form of AgI

A

really fast

26
Q

when experimenting rates of substitution why do you use ethanol

A

it acts as a a solvent

27
Q

why is hydrolysis slower in different haloalkanes

A

because more energy is needed to break the C- halogen bond

27
Q

what is the method for rates of substitution (hydrolysis)

A
  1. Place a measured sample of each halogenoalkane, (equal molar amounts), into separate test tubes and place in to a water bath at 50oC
  2. Into another test tube place a solution of ethanol, water and aqueous silver nitrate and place in the same water bath.
  3. Once at equal temperature add equal volumes of the ethanol mixture and haloalkane solutions together.
  4. Time how long it takes for each precipitate to form
28
Q

what are the reagent conditions and products formed from elimination of an haloalkane

A

· Reagent: NaOH or KOH

· Conditions: Hot & Ethanolic solvent

· Type of product: Alkene

29
Q

In the elimination reaction for a haloalkane what do OH- ions act as

A

a base (electron acceptor)

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