Haloalkanes Flashcards

1
Q

What is a haloalkane?

A

A compound containing carbon, hydrogen and at least one halogen

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2
Q

Why is the carbon-halogen bond polar?

A

Halogen atom more electronegative than the carbon atom
Uneven distribution of electrons, with electrons closer to the halogen
Separation of charge= polarity

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3
Q

Define, fully, a nucelophile

A

An atom or group of atoms which are attracted to an electron deficient species (carbon atom) where it donates an electron pair to form a new covalent bond

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4
Q

Give 3 examples of a nucleophile

A

Hydroxide ions
Water molecules
Ammonia molecules

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5
Q

What is nucleophilic substitution?

A

When haloalkane reacts with a nucleophile, the nucleophile replaces the halogen atom in a substitution reaction. A new compound is formed with a different functional group.

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6
Q

What is hydrolysis?

A

A chemical reaction involving water or aqueous solution of a hydroxide that causes the breaking of a bond within a molecule.

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7
Q

Explain the 6 basic steps of nucleophilic substitution

A

1) Nucelophile approaches carbon atom attached to the halogen on the opposite side to the halogen
2) The direction of attack by OH- ion minimises repulsion between the halogen and the OH- ion
3) A lone pair of electrons on the hydroxide ion is attracted to and donated to the carbon atom
4) A new bond is formed between the oxygen and the carbon atom
5) Carbon-Halogen bond breaks by heterolytic fission
6) New organic product is an alcohol. Halide ion formed on the side.

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8
Q

How are haloalkanes converted into alcohols?

A

Sodium Hydroxide

Heated under reflux

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9
Q

What does the rate of hydrolysis depend on?

A

Strength of carbon-halogen bond in haloalkane

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10
Q

Which carbon-halogen bond is the most reactive? Why?

A

Carbon-Iodine, the bond enthalpy is the lowest, and so it is the weakest bond and requires the least energy to overcome.

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11
Q

Briefly explain the experiment that occurs to measure rate of hydrolysis of haloalkanes

A

Add aqueous silver nitrate to the solution of haloalkane
As reaction occurs the silver and halogen ions will combine to form precipitate in form Ag(+)+ X(-)= AgX(s)
Nucleophile in reaction is water
Carry out in presence of ethanol solvent to ensure one mixture forms not with separated layers

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12
Q

Give six uses of organohalogen compounds

A
Pesticides
Dry Cleaning
Making polymers
Fire retardants
Refrigerants
General Solvents
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13
Q

What is the role of the chemical ozone?

A

To absorb most of the biologically damaging ultraviolet radiation

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14
Q

What are the three risks of UV-B radiation to humans?

A

Skin Cancer
Increased genetic disorders
Eye damage

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15
Q

What does it mean for ozone to be in a steady state?

A

The formation of ozone is occurring at the same rate ozone is being broken down

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16
Q

Give 3 uses of CFC’s

A

Refrigerants
Air conditioning units
Aerosol Propellers

17
Q

Why are CFCs stable?

A

Strength of carbon-halogen bonds within the molecules

18
Q

Where do CFCs remain stable until? Then what happens?

A

Stratosphere

CFCs break down forming chlorine radicals, catalysing the breakdown of the ozone layer

19
Q

Why are there concerns CFCs are continuing to cause damage?

A

Not every country has banned them

Longevity in the troposphere

20
Q

What does UV radiation do to CFCs?

A

Provides sufficient energy to break a carbon-halogen bond in CFCs by homolytic fission to form radicals

21
Q

What is photodissociation?

A

Radiation initiating the breakdown of a compound

22
Q

Which other radical catalyses the breakdown of ozone?

A

Nitrogen Oxide

23
Q

Where is Nitrogen Oxide formed?

A

Naturally in lightning strikes

Aircraft travel