halogenoalkanes Flashcards

1
Q

general formula halogenoalkanes

A

CnH2n+1Hal

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2
Q

functional group

A

C-Hal

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3
Q

what does the presence of the polar bond in halogenoalkanes mean

A

they’re more reactive than alkanes

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4
Q

3 uses of halogenoalkanes

A
  • refrigerants
  • solvents
  • pharmaceuticals
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5
Q

how are halogenoalkanes named

A

after the parent alkane with the prefix chloro, bromo, iodo etc.

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6
Q

what must be indicated if there are more than 3 carbon atoms in the molecule

A

the position of the halogen

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7
Q

what must be indicated if 2 or more halogens are present

A

their positions in the chain

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8
Q

how are the halogens named if there are 2 of them in the chain and they are different

A

in alphabetical order

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9
Q

what 2 reactions do halogenoalkanes take part in

A

nucleophilic substitution and elimination

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10
Q

what is the halogen atom replaced with in a nucleophilic substitution reaction

A

by a new group of atoms

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11
Q

nucleophile

A

electron pair donor

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12
Q

why do halogenoalkanes take part in nucleophilic substitution

A

the carbon is bonded to a halogen and so it is rendered electron deficient

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13
Q

where does the nucleophile donate its pair of electrons to in nucleophilic substitution

A

the delta plus c atom to form a new bond

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14
Q

how does the C-Hal bond break in nucleophilic substitution and what does it form

A

Heterolytic fission

halide ion formed

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15
Q

examples of common nucleophiles

A

hydroxide
cyanide
ammonia

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16
Q

what do halogenoalkanes react with aqueous hydroxides to form

A

alcohols

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17
Q

what is the reaction between halogenoalkanes and aqueous hydroxides often referred to as

A

hydrolysis

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18
Q

hydrolysis

A

the breaking of a bond using water

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19
Q

what is the reagent in nucleophilic substitution with aqueous hydroxides

A

the hydroxide

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20
Q

what conditions are needed for nucleophilic substitution using hydroxide

A

warm and aqueous

21
Q

general equation for the nucleophilic substitution between halogenoalkane and hydroxide

A

R-Hal + NaOH > R-OH + NaHal

22
Q

reagent for nucleophilic substitution between halogenoalkane and cyanide

A

cyanide ion

23
Q

conditions for nucleophilic substitution between halogenoalkane and cyanide

A

warm and ethanolic

24
Q

general equation for for nucleophilic substitution between halogenoalkane (bromo) and (potassium) cyanide

A

RBr + KCN > RCN + KBr

25
what does reacting a halogenoalkane with cyanide increase
the length of the carbon chain
26
what do halogenoalkanes react with excess ammonia to form
amines
27
reagent for nucleophilic substitution between halogenoalkane and ammonia
NH3
28
conditions for nucleophilic substitution between halogenoalkane and ammonia
ethanolic and warm
29
general equation for nucleophilic substitution between halogenoalkane and ammonia
R-Hal + 2NH3 > RNH2 + NH4 + Hal-
30
what does the rate of substitution reactions of halogenoalkanes depend on
the c-hal bond enthalpy
31
what does a halogenoalkane react to form in an elimination reaction
an alkene
32
elimination
a reaction in which an atom/group of atoms is removed from a reactant
33
reagent for elimination reaction with halogenoalkanes
hydroxide
34
conditions for elimination reaction with halogenoalkanes
HOT and ethanolic
35
sequence of events in elimination reactions with halogenoalkanes
- halogen atom always removed - H atom from an adjacent C atom also removed - double bond forms between the two C atoms
36
what is the role of the hydroxide in elimination with halogenoalkanes
base
37
substitution vs elimination using hydroxide: conditions
s: warm and aqueous e: hot in ethanol
38
substitution vs elimination using hydroxide: major product
s: alcohol e: alkene
39
substitution vs elimination using hydroxide: role of OH-
s: nucleophile e: base
40
what properties of chloroflourocarbons make them suitable for use as solvents and refrigerants
non-toxic and low reactivity
41
what did the properties of chloroflourocarbons lead to
the depletion of the ozone layer
42
where does ozone form
in the upper atmosphere
43
how does ozone form
from the reaction of oxygen atoms with oxygen molecules
44
equation for formation of ozone:
O + O2 > O3
45
why is the ozone layer beneficial
it absorbs UV radiation that can cause skin cancer
46
what did scientists discover that waste CFCs didnt do
break down easily and so would rise up to the upper atmosphere and break down to form chlorine radicals
47
what do chlorine radicals do and what has this led to
catalyse the breakdown of ozone led to a hole in the ozone layer
48
equation for chlorine radicals reacting with ozone
O3 + Cl. > O2 + ClO. ClO+ O3> 2O2 + Cl.
49
what alternatives to CFCs are now used
organohalogens that don't contain chlorine