Halogenoalkanes 3.3.3 Flashcards
Why do haloalkanes have a higher boiling point than alkanes
Alkanes only have van der waals forces betweeb molecules
Haloalkanes have dipole dipole forces and vdw forces
Dipole dipole force is a stronger imf than vdw forces so more energy is required to overcome the force
Why are fluoroalkanes the least reactive
C-F bond is very strong
Bond enthalpy of bond us very high so more energy required to break the bond
What is the general formula of haloalkanes
CnH2n+1X
Why is the carbon in a haloalkane susceptible to the attack by a nucleophile
Carbon atom is electron deficient so it is slightly positively charged (so it’ll attract the nucelophile)
What is a nucleophile
A species that has a lone pair of electrons with which it can form a bond by donating its electrons to an electron deficient carbon atom
What are the 3 different nucleophiles and what are its charges
OH- Hydroxide ion (negatively charged ion)
CN- Cyanide ion (negatively charged ion)
NH3 Ammonia (neutral)
What happens during the nucleophylic substitution
Nucleophiles replace the halogen atom in the haloankane
The C-X bond breaks during this reaction
Yaya Samsung notes
Yaya
What are the products formed when haloalkanes react with aquoeus potassium hydroxide(KOH) or Sodium hydroxide(NaOH)
Alcohol and potassium halide or sodium halide
What are the conditions needed when haloalkanes react with hydroxide ion
Aquoeus and heat under reflux
Why must there be aqueous conditions when haloalkanes react with hydroxide ion
Use potassium hydroxide as the example
So potassium hydroxide dissociates to form hydroxide ion and potassium ion
What are the conditions needed when a haloalkane Reacts with a cyanide ion
Heat under reflux
Ethanol used as solvent
What is the main product of nucleophillic substitution with cyanide ion
Alkanenitrile(if its a cylcoalkane, don’t change the carbon length part)
What are the conditions needed during nucleophillic substitution with Ammonia
Heat under reflux
Ethanol as solvent
Excess ammonia
What is the name of the main product of nucleophillic substitution with ammonia
Alkylamine
In nucleophillic substitution with ammonia, what does the first and second ammonia act as
First ammonia acts as a nucleophile
Second ammonia acts as a base(proton accepter)
Lala Samsung notes
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What are the 3 ways haloalkanes can be categorised
What is the key feature about the first and last
Primary haloalkane (more likely to undergo nucleophillic substituion)
Secondary haloalkane
Tertiary haloalkane (more likely to undergo elimination reaction)
Why are tertiary haloalkanes less likely to undergo nucleophillic substitution
The alkyl groups are electron releasing
Positive inductive effect by the alkyl groups makes the carbon less electron deficient so less likely to undergo nucelohillic substitution
What are the conditions needed in elimination reaction
Heat under reflux
Hot ethanol
In an elimination reaction, what does the reaction between haloalkane and potassium or sodium hydroxide form
Alkene, potassium or sodium halide and water
What does hydroxide ion act as in ethanol and aqueous solutions
Ethanol - base
Aquoes nucelophile
Elimination Samsung notes
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Why is ozone important for humans
It absorbs harmful UV light which protects humans from skin cancer and sunburn
What is present in the atmosphere that causes ozone to be destroyed
Is this man made or natural
Chlorofluorocarbons (CFCs)
Man made
What are the 3 equations when ozone is being destroyed
Start with CFCl3
What is the overall equation
CFCl3 -> ●Cl + ●CFCl2
●Cl + O3 -> O2 + ●ClO
●ClO + O3 -> ●Cl + 2O2
2O3 -> 3O2
UV light causes CFCs to break
Which bond is broken to form what
C-Cl bond is broken to form a chlorine radical
What is the Montreal protocol
What safer alternatives to CFCs have been formed
-Essential agreement to phase out CFCs in 200 countries
Hydrofluorocarbons(HFCs), trifluoromethane
How do halogenated organic Compounds contribute towards global warming
Polar moelcules vibrate when infrared radiation hits them so they are able to absorb infrared radiation which causes global warming
