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Chemistry L6 > Halogenoalkanes > Flashcards

Halogenoalkanes Flashcards

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1
Q

What happened when alkanes react with uv-light?

A

they form halogenoalkanes and hydrogen halides

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2
Q

What is the equation fir the reaction with alkanes in uv-light

A

halogen + alkane > halogenoalkane + hydrogen halide

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3
Q

what is a free radical?

A

reactive species due to the pre of an unpaired electron

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4
Q

what happened in the initiation step?

A

uv light causes a covalent bond between halogens atoms to break and this creates 2 halogen radicals

X2 > 2X•

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5
Q

What happens in the first propagation step?

A

The halogen radical reacts with an alkane
radical removes a hydrogen from the alkane creating a hydrogen halide molecule

CH4 + X• > •CH3 + XH

alkane is left as a alkyl radical

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6
Q

What happens in the second propagation step?

A

alkyl radical reacts with a halogen molecule and created a halogenoalkane
remaining halogen is left as a halogen radical

•CH3 + X2 > •X + CH3X

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7
Q

What happens in the termination step?

A

2 radicals will react to form a molecule
either:

two halogen radicals
halogen radical + alkyl radical
two alkyl radicals

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8
Q

what are short chain chlorofluorocarbons used for?

A

they are gases and were used fir refrigerators

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9
Q

what are long chain chlorofluorocarbons used for?

A

dry cleaning and de-greasing solvents

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10
Q

what happened when chlorofluorocarbons are decomposed?

A

they form chlorine free radicals when in the atmosphere

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11
Q

why is the ozone layer important?

A

absorbs harmful uv radiation

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12
Q

how is a chlorine radical formed?

A

C-Cl breaks in the presence of uv radiation to form Cl•

R-Cl > R• + Cl•

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13
Q

What is the equation for the decomposition of ozone?

A

Cl• + O3 > ClO• + O2

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14
Q

What is the equation for ClO• attacking more radicals?

A

ClO• + O3 > 2O2 + Cl•

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15
Q

What is the overall equation to show ozone breakdown?

A

2O3 > 3O2

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16
Q

What is a primary halogenoalkane?

A

halogen is bonded to a C that is bonded to 1 other C

17
Q

What is a secondary halogenoalkane?

A

halogen is bonded to a C that is bonded to 2 other Cs

18
Q

What is a Teritary halogenoalkane?

A

halogen is bonded to a C that is bonded to 3 other Cs

19
Q

What is a mechanism?

A

pictorial representation of the movement of a pair of electrons during a chemical reaction

20
Q

What is a nucleophile?

A

donate electron pairs to electrophiles

21
Q

What happens in nucleophilic substitution?

A
  • nucleophile donates lone pair to carbon and forma a covalent bond
  • carbon gives electrons back to halogen and bond breaks
22
Q

What are the conditions for nucleophilic substitution?

A

warm aqueous solution

23
Q

What are the conditions for nucleophilic substitution to form amines?

A

warmed in excess of ammonia

24
Q

What is the overall equation for nucleophilic substitution to form amines?

A

CH3CH2X + 2NH3 > CH3CH2NH2 + NH4X

25
Q

what is formed when a primary amine recast with another halogenoalkane

A

secondary amine

26
Q

what forms when a secondary amine reacts with another halogenoalkane?

A

tertiary amine

27
Q

what happened when a tertiary amine reacts with another halogenoalkane?

A

quaternary ammonium salt

28
Q

What are the conditions for elimination?

A

hot ethanol

29
Q

What is formed after elemination

A

an alkene and water

30
Q

What are the steps of elimination?

A
  • hydroxide removes a hydrogen from an adjacent carbon to the halogen
  • electrons in C-H move to the C-C bond to create a double bond
  • electrons in C-Halogen move into halogen breaking the bond and forming a halide ion

Chemistry L6 (17 decks)

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