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A-level Chem > Haloalkanes > Flashcards

Haloalkanes Flashcards

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1
Q

Define nucleophile

A

Electron pair donor

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2
Q

Why are halogenoalkanes reactive

A

Halogens are more electronegative than carbon creating a polar bond
This means nucleophiles can attack the bond

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3
Q

Nucleophile examples (3)

A

Ammonia
Hydroxide ions
Cyanide ions

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4
Q

Halogenoalkanes reacting with hydroxide ions conditions and overall reaction to form alcohols

A

Warm aqueous sodium hydroxide
Reflux
R-X + NaOH -> ROH + NaX

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5
Q

Halogenoalkanes reacting with cyanide ions conditions and overall reaction to form nitriles

A

Warm ethanolic Potassium cyanide
Reflux

R-X + KCN -> RCN + KX

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6
Q

Halogenoalkanes reacting with ammonia conditions and other products when amines are formed

A

Heat with ethanolic ammonia
Excess ammonia

Produced an amine and an ammonium ion with the halogen ion

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7
Q

Halogenoalkanes become more or less reactive down the group?

A

More

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8
Q

What determines reactivity of halogenoalkanes?

A

Bond enthalpy, not bond polarity
Bond with the lowest enthalpy is the easiest bond to break

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9
Q

Halogenoalkanes reacting with hydroxide ions conditions and overall reaction to form alkenes

A

Warm ethanolic sodium hydroxide
Reflux

CH3CHXCH3 + KOH -> CH2CHCH3 + H2O + KX

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10
Q

How to know if substitution or elimination reaction will occur

A

Substitution to make an alcohol if water is the solvent
Elimination to make an alkene if ethanol is the solvent

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11
Q

What is a CFC?

A

Chlorofluorocarbons
Stable molecules (until broken down by UV) that have had all their hydrogens replaced by chlorine and fluorine

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12
Q

Why are C-Cl bonds broken easiest by UV in CFCs

A

They have the lowest bond enthalpy

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13
Q

CFC and ozone free radical substitution mechanism, overall equation and what is the catalyst?

A

I: CCL3F -UV> •CCl2F + •Cl

P: •Cl + O3 -> ClO• + O2
ClO• + O3 -> •Cl + 2O2
T: 2•Cl -> Cl2

Overall: 2O3 -> 3O2
Catalyst: •Cl

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14
Q

How did we use CFCs?

A

They were used in fridges as refrigerant and propellants in deodorants

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15
Q

Why did we stop using CFCs, what do we use now and why?

A

It was damaging the ozone layer and risks outweighed benefits
Ozone absorbs most harmful UV radiation that causes skin cancer
Now: HFCs are used (hydrofluorocarbons) as they don’t have chlorine in them

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A-level Chem (35 decks)

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