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chemistry > haloalkanes > Flashcards

haloalkanes Flashcards

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1
Q

What are haloalkanes

A

Saturated organic compounds that contain carbon atoms and at least one halogen atom

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2
Q

Are halogenalkanes soluble in water?

A
  • yes
  • Halogens are more electronegative than carbon so the carbon-halogen bond is polar
  • The positive carbon is electron deficient so it can be attacked by a nucleophile
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3
Q

Do halogenalkanes have a polar bond? Why?

A
  • Yes contain a polar bond

- Halogen has a higher electronegativity than C so halogen-C bond is polar

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4
Q

What type of intermolecular forces do halogens have? Why?

A

Permanent dipole-dipole and London forces of attraction

C-X bond polarity creates permanent dipoles

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5
Q

When would halogenalkanes have higher boiling points?

A
  • Increased carbon chain length

- Halogen further down group 7

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6
Q

What is the most important factor in determining halogen reactivity?

A

The strength of the carbon halogen bond

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7
Q

What would bond polarity suggest the order of reactivity would be in haloalkanes?

A

C-F would be most reactive as most polar bond

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8
Q

What would bond enthalpies suggest the order of reactivity would be?

A

C-I would be most reactive as it has the lowest bond enthalpy

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9
Q

What is a primary halogen?

A

The halogen atom is present at the end of the chain

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10
Q

Define nucleophile

A

Electron pair donor

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11
Q

Give 3 examples of nucleophiles

A
  1. OH-
  2. CN-
  3. NH3
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12
Q

What is nucleophilic substitution?

A

A reaction where a nucleophile donates a lone pair of electrons to a partially positive C atom, the partially negative atom leaves molecule and is replaced by nucleophile

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13
Q

What reactant often produces hydroxide ions for hydrolysis?

A

Water

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14
Q

What fission does water undergo to produce OH-

A

Heterolytic fission

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15
Q

What are CFCs?

A

Chlorine-fluoro-carbons, haloalkanes contains C,F and Cl only

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16
Q

What is the problem with CFCs

A
  • Unreactive under normal conditions, they catalyse the breakdown of ozone in the atmosphere via free radical substitution
17
Q

What is the main function of ozone layer

A

Provides protection from harmful UV radiation

18
Q

How do CFCs break the ozone layer down

A

Free radical substitution

19
Q

Write an equation for the overall decomposition of ozone into oxygen (O2)

A

2O3 -> 3O2

20
Q

How do you produce alcohol from haloalkanes

A
  • By a nucleophilic substitution reaction
  • Use a warm aqueous alkali like NaOH to hydrolyse the haloalkane to an alcohol
  • The reaction has to occur under reflux
21
Q

What is needed for the hydrolyzation of haloalkanes to alcohols

A

Warm aqueous alkali like sodium hydroxide (NaOH) or potassium hydroxide (KOH)

22
Q

What happens to the reactivity of haloalkenes down group 7?

A

The reactivity increases

23
Q

What are the properties of chlorofluorocarbons (CFCs)

A
  1. Stable
  2. Volatile
  3. Non-flammable
  4. Non-toxic
24
Q

Why are holes in the ozone layer harmful

A

Because they allow more harmful UV radiation to each Earth

25
Q

What do free nitrogen oxides radicals do?

A

NO free radicals from nitrogen oxides destory the ozone

26
Q

How are holes in the ozone layer formed

A
  • CFS in the upper atmosphere absorbs UV radiation and split to form chlorine-free radicals
  • These radicals catalyze the destruction of ozone, they destroy ozone molecules and are then regenerated to destroy more ozone
27
Q

Describe what alternatives to CFCs are used

A
  • HCFCs and HFCs are being used as temporary alternatives until safer products are developed
  • Hydrocarbons are used
28
Q

What are the disadvantages of using HCFCs and HFCs as alternatives to CFCs

A
  1. They are broken down in the atmosphere in 10-20 years, they still damage the ozone layer but their damage is smaller than the CFCs
  2. HFCs and HCFCs are greenhouse gases
29
Q

What are the advantages of using HFCs over HCFCs

A

HCFS are also broken down in the atmosphere, unlike HCFCs they don’t contain chlorine so they don’t affect the ozone layer

30
Q

What did the government do to prevent the use of CFCs internationally?

A

The Montreal Protocol of 1989 phased out the use of CFCs and other ozone-destroying haloalkanes by the year 2000.

31
Q

What is the greenhouse effect

A

It is when various gases in the atmosphere that contain C=O, C-H or O-H bonds are able to absorb infrared radiation and re-emit it in all directions

32
Q

What are the main greenhouse gases

A
  1. Water vapor
  2. Carbon dioxide
  3. Methane
33
Q

What do higher concentrations of greenhouse gases due to industrialization mean to global warming?

A

Higher concentrations of greenhouse gases mean more heat is being trapped and the Earth is getting warmer (global warming)

34
Q

Define global warming

A

Global warming is responsible for recent changes to climates

35
Q

How are governments working to reduce their greenhouse gas emissions?

A
  • 1997 the Kyoto protocol was signed which means industrialized countries promised to reduce their greenhouse gas emissions to agreed levels, 50% by 2050
  • The UK government created policies to use more renewable energy supplies such as wind and solar farms to reduce emission

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