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chemistry > haloalkanes > Flashcards

haloalkanes Flashcards

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1
Q

what is hydrolysis

A

hydrolysis is a reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds

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2
Q

what ways can hydrolysis happen with haloalkanes

A
  • heating with silver nitrate and ethanol added
  • heating under reflux with an aquous alkali eg naoh
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3
Q

what is the mechanism for this reaction called

A

nucleophillic substitution

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4
Q

what is a nucleophile

A

an ion or molecule which is strongly attracted to a region of positive charge in something else . it is an electron pair donor

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5
Q

draw the mechanism for bromoethane reacting with NaOH

A
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6
Q

what happens when a haloalkane reacts with a nucleophile

A

the nucleophile replaces the halogen in a substitution reaction

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7
Q

why does the halogen - carbon bond break and not one of the h-c bonds

A

the weakest bond breaks and because C-H bonds are very strong the halogen - carbon bond breaks

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8
Q

what happens to the polarity of the haloalkanes

A

polarity decreases down the group because electronegativity increases as atomic radius increases , electron sheilding increases and ability to gain an electron decreases

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9
Q

which haloalkane bond has the weakest bond enthalpy

A

C-I because the attraction is weaker

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10
Q

how can you determine the rate of hydrolysis for different haloalkanes

A
  • the rates can be determined by heating the haloalkane with aqueous silver nitrate with ethanol added
    water in the silver nitrate solution acts as a nucleophile .
    and the ethanol acts as a common solvent ,. ensuring the silver nitrate and haloalkane mix together and react .
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11
Q

what happens as the hydrolysis reaction occurs

A

halide ions form . the silver nitrate reacts with it forming a precipitate of the silver halide

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12
Q

what is the equation for 1-chlorobutane and silver nitrate

A

C4H9Cl(Aq) + H20(l)–>C4H9OH + AgCl~(s)+HNO39aq)

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13
Q

what are organohalogen compounds

A

molecules that contain atleast one halogen atom joined to a carbon chain

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14
Q

why are organohalogen compounds of slight concern

A

because they are not broken down naturally in the enviroment

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15
Q

where is the ozone layer found

A

at the outer edge of the stratosphere at a height that varies of 10-40km above earths surface

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16
Q

what does it do which is good

A

it absorbs damaging uv rays from the sun (UV-B) stopping them reaching the earths surface

17
Q

why is depletion of the ozone layer bad

A

more uv-b will reach our planet and damage genetics and cause a greater risk of skin cancer in organisms

18
Q

how does uv break oxygen

A

O2-> 2O

19
Q

how is ozone formed

A

O2+O<—–> O3

20
Q

what are common uses of CFCs

A

coolants in fridges
propellants in aerosols
dry cleaning solvents

21
Q

why are CFCs very stable

A

because of the strong C-H bonds

22
Q

what decreases their stability

A

-being in the stratosphere forming radicals which catalyse the breakdown of the ozone layer

23
Q

what are CFCs

A

chlorofluoro carbons (haloakanes) molecules with all their hydrogens replaced by chlorine and fluorine

24
Q

why is the Cl-C bond broken first in CFCs

A

it has the weakest bond enthalpy

25
Q

what is the initiation step for the breakdown of ozone

A

CCl3F(g)—> .CCl2F(g) + .Cl(g)
by uv

26
Q

what are the 2 propagation steps for the breakdown of ozone

A

1) Cl .(g) + O3(g) —> O2(g) + ClO .(g)

2)ClO . (g)+ O (g)—> O2(g) + Cl.(g)

27
Q

what is the termination step for the breakdown of ozone

A

Cl. (g) + Cl. (g) –> Cl2

28
Q

whats the overall equation for the breakdown of ozone

A

2O3 <—-> 3O2

29
Q

how is Cl. a cataylst

A

because it is reformed

30
Q

what other radials destroy ozone

A

nitrogen oxides formed from vehicle emissions and thunder storms can destroy ozone

31
Q

what is the initation equation for NO2 breakdown

A

NO2 (g) —> NO.(g) + O(g)

32
Q

what are the two propagation steps for the breakdown of NO2

A

1) NO.(g) + O3(g)—>O2 +NO2.
2) NO2.(g) + O –>O2 + NO.

33
Q
A

chemistry (24 decks)

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