Haloalkanes Flashcards

1
Q

Electronegativity definition

A

Power or an atom to attract the 2 elections in a covalent bond

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2
Q

3 factors effect ion electronegativity

A

Number of protons
Atomic radius
Shielding

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3
Q

How does number of protons affect electronegativity?

A

Stronger attraction between negative electrons in bonding pair and positive nucleus

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4
Q

How does atomic radius affect electronegativity ?

A

Closer the bonding pair to nucleus stronger the attraction

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5
Q

How does shielding affect electronegativity ?

A

More shells between bonding pair and nucleus, weaker attraction

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6
Q

Electron negativity down a group

A

Decreases

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7
Q

Explaination for electronegativity down a group

A
  • atoms bigger
  • more shielding
  • weaker attraction between bonding pair and nucleus
  • decreases
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8
Q

Electronegativity across a period

A

Increases

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9
Q

Explaination for electronegativity across a period

A
  • atoms smaller
  • more protons
  • stronger attraction between bonding pair and nucleus
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10
Q

When does a non-polar covalent bond happen?

A

Two atoms in covalent bond have same electronegativity

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11
Q

When do polar covalent bonds happen?

A

Two atoms in covalent bond have different electronegativity

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12
Q

What is a non-polar covalent bond?

A

Covalent bond where 2 electrons are shared equally

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13
Q

What is a polar covalent bond?

A

Covalent bond where the 2 electrons are not shared equally

The more electronegative the greater the electron share

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14
Q

What is a bond dipole moment?

A

A measure of the strength + direction of the polarity in the bond

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15
Q

What does the bigger difference in electronegativity mean for bond dipole moment?

A

The bigger the bond dipole moment

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16
Q

3 things that determine electronegativity

A
  • Nuclear charge
  • Distance between nucleus + outer electron shell
  • shielding by inner electron shells
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17
Q

Electronegativity across a period

A

Increases

  • more protons = stronger nuclear charge
  • smaller atomic radius
  • stronger attraction between nucleus + outer electron shell
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18
Q

Electronegativity down a group

A

Decreases

  • more shielding
  • larger atomic radius
  • weaker attraction between nucleus + outer electron shell
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19
Q

bond polarity definition

A

Unequal sharing or electrons between atoms rhat are covalently bonded

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20
Q

What is charge separation referred to as?

A

Dipole

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21
Q

Test for polarity

A

Balloon next to tap

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22
Q

3 types of halogen Alkanes

A

Primary
Secondary
Tertiary

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23
Q

What are the haloalkane types dependant on?

A

Bonding in the carbon atom to which the halogen atom is bonded to

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24
Q

What do bond enthalpies show?

A

Bond strongness

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25
Q

How are halogen allowances formed?

A

When a halogen takes place of hydrogen in an alkane

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26
Q

General halogen alkanes formula

A

CnH2n+1 (R-X)

27
Q

What can haloalkanes be used for?

A

Solvents (dry cleaning)
Refrigerants
Pesticides

28
Q

What is the ozone layer beneficial for?

A

it filters out mush of the suns harmful UV radiation

29
Q

What does CFCs stand for?

A

Chloroflurocarbons

30
Q

What do man made CFCs do?

A

Cause a hole in ozone lay a

31
Q

What do chlorine free radical atoms do?

A

Catalyse the decomposition of ozone

32
Q

Cl. free radical equation

A

Cl. + O3 -> ClO. + O2
ClO. + O3 -> 2O2 + Cl.
2O3 -> 3O2

33
Q

What does regenerated Cl radical mean?

A

Means 1 Cl radical could destroy many thousands of ozone molecules

34
Q

What bond is not affected by UV?

A

C-F

35
Q

Why is c=c bond not 120 degrees?

A

Higher density so repels H electrons

36
Q

What is a Z isomer?

A

Together

37
Q

What is an E isomer?

A

Opposite

38
Q

What is hydrolysis?

A

Splitting of a molecule using water

39
Q

What is the reactivity of the C-X bond?

A
  • C-X bond broken when haloalkane reacts

- reactivity depends on how easy C-X bond is to break

40
Q

What 2 factors determine how easy C-X bond is to break?

A
  • C delta + - X delta - bond polarity

- C-X bond enthalpy

41
Q

What results in a electron - deficient carbon?

A

More electronegative halogen removes charge from carbon it is bonded to

42
Q

What is electron - deficient carbon vulnerable to?

A

Vulnerable to attack by electron-rich reagents called nucleophiles

43
Q

What would we expect more reactive electronegative halogens to give?

A

More reactive haloalkanes

44
Q

What is the deciding factor for rate of hydrolysis?

A

Bond enthalpy

45
Q

Bond enthalpies from strongest to weakest

A
C-F
C-H
C-Cl
C-Br
C-I
46
Q

What will be more reactive is the bond polarity is important to the reaction?

A

R-F

47
Q

What will be more reactive is bond enthalpy is important to the reaction?

A

R-I

48
Q

What happens in a nucleophilic substitution reaction in hydrolysis?

A

A nucleophilic attacks a polar molecule + kicks out a functional group + settles itself down in its place

49
Q

General equation for nucleophilic substitution of halogen alkane

A

CH3CH2X + Nu- -> CH3 CH2 Nu+ X-

50
Q

What are the 3 nucleophiles

A

OH- (alcohol)
CN- (nitrile)
NH3- (amines)

51
Q

Hydrolysis of haloalkane method

A
Put test tubes of haloalkane + ethanol in hot water bath 
add silver nitrate 
White = chloride 
Cream = bromide 
Yellow = iodide
52
Q

What does R replete sent in nucleophilic substitution?

A

Alkyl group

53
Q

What does X represent in nucleophilic substitution?

A

Any halogen

54
Q

What does mechanism of nucleophilic substitution depend on?

A

Depends on C-X bonds strength

55
Q

What is a nucleophile?

A

A particle with a lone pair of electrons which can donate to form a bond

56
Q

Nucleophilic aubstitution steps

A

1) halogenoalkane undergoes nucleophilic substitution
2) lone pair of electrons on nucleophile attracted to electron deficient carbon
3) curly arrows show movement of pair of electrons
4) nucleophile causes electron in C-X bond to repel toward more electronegative halogen
5) forms halide ions

56
Q

Free radical 3 steps

A

First propagation step
Second propagation step
Termination

57
Q

Why do we use HFCs and not CFCs?

A

CFCs attached ozone layer + thinned down

58
Q

Structural isomer definition

A

Molecules with same molecular formula but different structures

59
Q

Acids, bases + alkali roles in elimination reaction in haloalkanes

A

Acid-proton donator
Base-proton acceptor
Alkali-soluble base

60
Q

What does nucleophilic substitution with haloalkane form?

A

Alcohol

61
Q

What happens when an OH- acts as a base?

A

Removes H+ from the haloalkane

Elimination rather than substitution

62
Q

Conditions for elimination

A
  • heat
  • ethanol as a solvent (no water present)
  • concentrated potassium hydroxide