28) Organic synthesis Flashcards
What is a nitrile group?
-CN
haloalkane + NaCN or KCN (in ethanol ->
nitrile + Na halide or K halide
In the nucleophilic substitution mechanism for the formation of a nitrile, where are the 2 curly arrows?
from the :C- triple bond N to the partially positive carbon
from the carbon - halogen bond to the partially negative halgogen
aldehyde/ketone + HCN ->
hydroxynitrile (cyanohydrin)
In the nucleophilic addition mechanism for the formation of a hydroxynitrile, where are the 4 curly arrows?
from the :C- triple bond N to the partially positive carbon
from the C=O bond to the partially negative O
from the negative :O- to the partially positive H of a water molecule
from the H-O bond of the water molecule to the partially negative O of the water molecule
Give an equation for the reduction of a nitrile and state the catalyst
nitrile + 2H2 -> amine
Ni catalyst
Give an equation for the hydrolysis of a nitrile and the conditions required
nitrile + dilute aqueous acid -> carboxylic acid
heat
Name two methods of forming carbon-carbon bonds to benzene rings
alkylation and acylation
Define alkylation
reaction that transfers an alkyl group from a haloalkane to a benzene ring, taking place in the presence of a Friedel-Crafts catalyst
Define acylation
reaction of benzene with an acyl chloride in the presence of an aluminium chloride catalyst to form a ketone
Define filtration under reduced pressure
technique for separating a sold product from a solvent or liquid reaction mixture
State 5 key pieces of equipment need to carry out filtration under reduced pressure
Buchner flask Buchner funnel pressure tubing filter paper access to filter or vacuum pump
Define recrystallisation
technique to remove impurities from the solid product obtained after filtration (using the minimum volume of hot solvent)
Define melting point determination
technique to identify whether a solid compound is pure
State a feature of a pure sample
very sharp melting range
Define melting range
difference between temperature at which the sample begins to melt and at which melting is complete
Describe the 2 features of a sample containing impurities
wide melting range
lower melting point
Describe the key steps of melting point determination
seal capillary tube (using Bunsen burner flame)
fill with dry, free-flowing crystals
take melting point by using electrically heated melting point apparatus or an oil bath / Thiele tube method
Describe the steps of using an electrically heated melting point apparatus
using a thermometer and rapid heat setting observe the sample through magnifying window
record melting point + allow apparatus to cool
using a second sample, set to low and raise temp slowly as melting point is approached for accurate determination of melting point
Describe the steps of using an oil bath / Thiele tube method
set up
attach capillary tube with sample to thermometer
insert/clamp thermometer
slowly heat using a micro-burner, when the solid starts to melt, remove heat and record temperature
alkane -> haloalkane
hydrogen halide
alkane -> primary alcohol
hydration
H3PO4/H2O
haloalkane -> primary alcohol
NaOH(aq)
haloalkane -> nitrile
NaCN
