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Organic Chemistry > 3.3 Halogenoalkanes > Flashcards

3.3 Halogenoalkanes Flashcards

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1
Q

What is a primary Haloalkane?

A

The carbon with halogen is attached to one alkyl group
I
C-C-I
I
Only one link from the CH2 to the alkyl

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2
Q

What is a secondary haloalkane?

A

Carbon with halogen is attached to two other groups
-C-C-C
I
Br

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3
Q

What is a tertiary haloalkane?

A

Carbon holding the halogen is attached to three other alkyl group
C
I
C-C-C
I
Br

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4
Q

What is the trend in haloalkane bond enthalpies?

A

Get weaker going down the group due to greater distance and shielding

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5
Q

What is hydrolysis?

A

Using water to break up a compound

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6
Q

What is the formula for the addition of silver nitrate?

A

Ag+ + X —> AgX

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7
Q

Why is iodine the fastest to form a precipitate?

A

It’s the biggest atom so weakest attraction (more distance and shielding) so precipitation is formed quicker

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8
Q

What colour precipitates does Iodine,Bromine and Chlorine form with silver nitrate?

A

Iodine- Yellow
Bromine- Cream
Chlorine- White

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9
Q

What is the definition of a nucleophile?

A

A negatively charge ion or an atom with a delta negative charge
Has a lone pair
Electron donator

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10
Q

What are the common nucleophiles?

A

Hydroxide ions- :OH-
Ammonia- :NH3
Cyanide- : CN

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11
Q

In a haloalkane nucleophillic substitution reaction what is the leaving group ?

A

Halide ion

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12
Q

What is the order of reactivity with Haloalkanes?

A

C - Hal bond determines reactivity
C-F stronger (fewer shells)

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13
Q

What do nucleophilic substitution of OH ions form?

A
  • Alcohols
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14
Q

What happens in nucleophilic substitution of OH?

A
  • Lone pair on the O
  • Attacks positive C atom
  • Halogen is replaced by OH
  • HYDROLYSIS
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15
Q

What happens if OH ions undergo nucleophilic substitution in water?

A
  • Reaction works same as normal
  • Slower than other reactions
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16
Q

What do CN- ions form with Haloalkanes?

A
  • Forms nitriles
17
Q

What happens in a nucleophilic substitution reaction with CN- ions?

A
  • Weakly nucleophilic
  • Partially positive carbon atom attacked by lone pair on CN-
18
Q

What happens to the length of the carbon chain in Nucleophilic Substitution with CN ions?

A

It increases as the CN adds another carbon to the halogen

19
Q

What conditions must CN- nucleophilic substitution reactions take place under?

A
  • Reflux conditions
  • Ethanol
20
Q

Why must CN- nucleophilic substitution not occur in aqueous conditions?

A
  • The water would act as a nucleophilic and take over
21
Q

What happens in the nucleophilic substitution of NH3

A
  • Lone pair on NH3 attacks partially charged Carbon
  • C-N bond replace C-Hal and has a positive charge
  • Annother Ammonia molecule then picks up a H+ from the NH3 leaving an amine group
22
Q

What conditions are required for NH3 to undergo nucleophilic substitution?

A
  • Ethanol
  • Excess Ammonia
23
Q

Why must there be excess Ammonia for NH3 nucleophilic substitution?

A
  • Because the amine group created is also nucleophilic
  • Would react again with haloalkane
  • To prevent further substitution
24
Q

What are formed as a by product of nucleophilic substitution with NH3?

A
  • Quartenery ionic salts
  • Extra H+ is picked up by NH3
  • Forms NH4 +
25
Q

What conditions are required for elimination?

A
  • Ethanol
  • Reflux reactions
  • OH-
    -Hot
26
Q

How does elimination work?

A
  • OH- uses its lone pair to bond with one of the hydrogens on the adjacent carbon to the halogen
  • electron pair from c - h forms a c-c double bond
  • Bromine takes pair of electrons and leaves as a Br-
27
Q

How do you name amines?

A
  • Add amino prefix to hydrocarbon
28
Q

Why does silver nitrate not form an immediate precipitate?

A

Lots of strong covalent bonds
No free ions

29
Q

Why is ethanol needed in elimination?

A

To act as a solvent

30
Q

Where does the water come from in Oh- elimination?

A
  • It is an aqueous solution
31
Q

What is the ozone formula?

A

O3

32
Q

What is the ozone layer?

A

A layer of ozone making up a protective layer protecting earth from harmful UV radiation

33
Q

Why is UV radiation harmful?

A
  • Can cause DNA damage
  • Cause of skin cancers
34
Q

How is ozone being formed and broken at the same rate without intervention of CFC’s?

A

O+O2 = O3 (reversible reaction)

35
Q

What did CFC’s used to be used in?

A
  • Coolants in fridges
  • Propellants in aerosols
  • Dry cleaning
36
Q

What are the features of CFC’s?

A
  • Contain cholorine,fluorine and carbon
  • Very stable (high bond enthalpy)
  • Non toxic
37
Q

What was decided at the Montreal Protocol?

A
  • 24 countries banned use of CFC’s
  • However some old fridges still contain them
38
Q

How do CFC’s destroy ozone?

A

CFCl3 (example) dissociates into CFCl2 and Cl free radicals
Cl’ + O3 —> ClO’ + O2
ClO’ + O —>Cl’ + O2

Overall 2O3 turns into 3O2

39
Q

What is the effect of one CFC molecule?

A
  • Can destroy thousands of O3

Organic Chemistry (18 decks)

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