ORGANIC - HALOGENOALKANES Flashcards

1
Q

What are halogenoalkanes

A

functional group which is a halogen atom. much more reactive than alkanes as the C in C-X bonds is e- deficient and the C-X bonds are weak

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2
Q

Halogenoalkanes boiling point trend

A

Increase with
- Chain length = longer chain greater the bp
- Down the group bp increase

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3
Q

Halogenoalkanes key points

A

Polar - due to permanent dipole-dipole forces
Larger molecule, more e- so stronger VdW forces

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4
Q

Nucleophilic substitution - nucleophile key points

A
  • A nucleophile is an electron-rich species that can donate a pair of electrons to form a covalent bond
  • it will attack a positively charged carbon atom
  • either negatively charged ion or contains a partially negative atom
  • contains a lone pair of electrons on the electronegative atom
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5
Q

Nucleophilic substitution - conditions

A

aqeous sodium or potassium hydroxide mixed with ethanol and the halogenoalkane
water is present
warm conditions
product is an alcohol

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6
Q

cyanide mechanism

A

reagent = potassium cyanide
product - nitrile
= look at notes for diagram

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7
Q

hydroxide mechanism

A

reagent = sodium hydroxide
product = alcohol
= notes for diagram

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8
Q

ammonia mechanism

A

reagent = ammonia
product = amine
second NH3 acts as a base and removes a proton. The pair of e- in the N-H bond are transferred to the N atom (bond breaks heterolytically) leaving the final product as an amine

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9
Q

what is nucleophilic elimination

A

the removal of a small molecule from organic molecule

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10
Q

nucleophilic elimination key points

A
  • hot, ethanoic KOH
  • loses X and H from adjacent C
  • forms alkene
  • OH- acts as a base not a nucleophile
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11
Q

nucleophilic elimination mechanism

A

notes

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12
Q

uses of halogenoalkanes

A

pvc
teflon
solvents
anaesthetics

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13
Q

what does ozone act as (importance)

A

Ozone in the upper atmosphere acts as chemical sunscreen absorbing a lot of UV radiation from sun - cause skin cancer and sunburj

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14
Q

ozone natural reactions

A
  1. O2 —> 2O(.)
  2. O2 + O(.) —> O3
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15
Q

What are chlorofluorocarbons

A

CFCs are:
- all H atoms replaced by either F or Cl
- used to be widely used as refrigerants (coolants)
- also in aerosols as the propellant gas
- CFCs can be very damaging to the ozone layer

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16
Q

Chlorofluorocarbons radicalisations

A
  • In the upper atmosphere in UV light presence the C-Cl bond within CFCs can be broken to form CL free radicals
    = CCl3F —> CCl2F(.) + Cl(.)
    These Cl(.) catalyse the breakdown of ozone
    = Cl(.) + O3 —> O2 + ClO(.)
    = ClO(.) + O3 —> 2O2 + Cl(.)
    = 2O3 —> 3O2
17
Q

Why are CFCs banned

A

Scientists demonstrated the CFCs were creating holes in the ozone layer