Topic 6 Organic Chem
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What happens in an elimination reaction
Halogenoalkane + X‐ —> alkene +MX + H20 M=metal from MOH so could be K or Na X=OH-
What are the conditions and reactions for halogenoalkanes reacting with NaOH to produce an alcohol
NaOH/KOH which is aqueous under reflux Heat This is a nucleoiphillic substitution reaction
Conditions when cyanide ions react with halogenoalkanes
Reagent:aqueous alcoholic KCN or NaCN Conditions:Reflux in aqueous alcoholic solution Ethanolic Product:Nitriles This is nucleophilic substitution
Conditions when halogenoalkanes react with ammonia
EXCESS aqueous ammonia Ethanol solvent Conditions: Reflux in aqueous alcoholic solution under pressure or a sealed tube Nucleophile:NH3 Product:amine Nucleophillic substitution
During an ammonia nucleophilic substitution does ammonium donate electrons to central Nitrogen or hydrogen in the 2nd step
Hydrogen as they are positively charged Not positive nitrogen because it has a negative dipole
Explain the 2 step mechanism of NS with ammonia
NH3 forms a bond with carbon and the C-X bond breaks ANOTHER NH3 forms a bond with Hydrogen and the N-H bond breaks
Why are halogenoalkane + NaCN reactions useful
Increases no of carbon atoms in chain
In the Halogenoalkane plus Ammonia reaction Explain why reactants are heated and sealed
Heated to increase ROR sealed to prevent loss of ammonia as its toxic
SN1 Reaction Characteristics
It means Nucleophilic Substitution The 1 means the RDS has order 1(one reactant) 2 steps with a slow step(RDS) More stable halogenoalkanes are more likely to do SN1 e.g tertiary are fastest Forms a Racemic mixture
SN2 Reaction characteristics
2 means RDS is 2nd order(so has 2 reactants in this step) 1 step reaction Primary halogenoalkanes are the most likely to undergo this Due to low steric hinderance Backside attack There is a Transition state Inversion of configuration
Why is pvc bad
Releases toxic fumes
How to set up and monitor a hydrolysis of a halogenoalkane
Add AgNO3 1cm³(after ethanol and RX) to a sample of Halogenoalkane(2 drops)with aqueous ethanol(1cm³) and place to heat in waterbath at 40-80 degrees Relative to rate of precipitation Measure time taken for silver halide precipitate to form Chloroalkane produces white precipitate Bromoalkane produces cream precipitate Iodoalkanes produces yellow precipitate
What does an Alkene+H2O(g) produce in the presence of an acid catalyst?
An alcohol
Thermal cracking conditions
High temp and pressure used at 1000 degrees Alkenes and alkanes as products Alkenes to make polymers
Catalytic cracking conditions
High temp and slight pressure Zeolite catalyst to lower temp Lower costs and speed Products are mainly aromatic hydrocarbons
What is reforming
Reforming is described as the processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion.
What is the problem with straight chain alkanes
Creates knocking in car engine This is where straight chain alkanes explode upon compression Adding cyclic alkanes reduces knocking Reforming requires a platinum catalyst
Biofuels what are they advantages and disadvantages
More renewable than crude oil Produces carbon neutral co2 when burnt Expensive Requires a lot of land
Biogas mean
Made from the break down of organic matter
Biodiesel mean
Made from refining oils and fats
Stereoisomerism
Have same structural formula but different arrangement of atoms E/Z
3 ways in which polymers can be used to improve sustainability
Recycle reuse Incineration to release and generate electricity Cracking to use as feedstock
Explain why using the apparatus for distillation instead of reflux is not efficient to produce ethanoic acid from ethanol
Ethanol will be produced to form an aldehyde Ethanal is more volatile Ethanol will distill before ethanoic acid can be formed
Why do haloalkanes have a higher boiling point than alkanes
The C-X bond is polar so it has permanent dipole dipole forces as well as London forces Alkanes only have london forces