Chapter 28 - Organic Synthesis
No description yet. This curated deck is ready for daily study.
Card preview (13)
How can we form nitriles? Reagents & conditions? What is significant about this reaction?
Nucleophilic substitution of haloalkanes React with NaCN or KCN, in ethanol solvent Extends the carbon-carbon chain
Draw the mechanism for chloromethane -> ethane nitrile
Notes!
What is the nucelophilic addition of aldehydes/ketones?
React with HCN (NaCn/H2SO4) to form a hydroxynitrile
What are the 2 reactions of nitriles?
• Can be reduced to amines by reacting with hydrogen in the presence of a Ni catalyst E.g. propane nitrile + 2H2 -> propyl amine • Hydrolysed to form carboxylic acids by heating with dilute aqueous acid E.g. butane nitrile + 2H2O + HCl -> butanoic acid + ammonium chloride
How does filtration under reduced pressure work?
• using a Büchner funnel, Büchner flask and vacuum pump • filter paper should be wet with solvent before filtration (ensures the filter paper sticks to the funnel) • rinse crystals and allow them to dry
Draw a labelled diagram to show the apparatus for filtration under reduced pressure?
Notes!
Why do we recrystallise?
• to purify a solid product • the desired product must have different solubility to the impurities
How does recrystallisation work?
• Minimum volume of hot solvent dissolves product and impurities • On cooling, product crystallises back out while impurities stay dissolved (important to cool at least to room temperature as some of the product may stay dissolved/not crystallise and so won’t be collected during filtration = lower yield) • Filter out product (under reduced pressure) and rinse crystals, then leave them to dry
What can melting points be used for?
To check whether a solid compound is pure If solid has impurities it will have a lower MP and will melt over a wider range of temperatures
How can we determine melting point?
• use a capillary tube and electrically heated melting point apparatus • as melting point is approached, heat slowly for an accurate determination
Why do we heat the capillary tube slowly?
If heated too quickly you may record a temperature that is higher than accurate melting range
What is another method for measuring melting point?
Oil bath/ Thiele tube Not water bath as it has a lower boiling point
How does an oil bath work?
• insert capillary tube and thermometer into a Thiele tube filled with oil • use a micro-burner to slowly heat arm of Thiele tube • when the solid starts to melt, remove the heat and record the temperature at which all the solid has melted