Chapter 28 - Organic Synthesis Flashcards
How are nitriles formed from haloalkanes?
Through nucleophilic substitution with a cyanide ion (CN-)
How are nitriles formed from aldehydes or ketones?
Via nucleophilic addition of hydrogen cyanide (HCN)
Why isn’t HCN used directly in synthesis reactions?
It is extremely poisonous
What mixture is used instead of HCN for safety and increased reaction rate?
Sodium cyanide (NaCN) and sulphuric acid (H2SO4)
How does a species of millipede use nitrile compounds so defensively?
It stores 2-hydroxy-2-phenylethanenitrile, which mixes with an enzyme to release HCN and benzaldehyde when attacked
What is filtration under pressure used for?
To separate a solid product from the solvent or liquid
What apparatus is used for filtration under pressure?
Buchner funnel, Buchner flask, pressure tubing, filter paper, and vacuum pumo
What are the steps for filtration under pressure?
Connect tubing to vacuum and flask
Fit tunnel tightly using ring/bung
Switch on pump and check suction
Place filter paper, wet with same solvent
Pour reaction mixture onto paper
Rinse beaker + crystals with solvent
Leave under suction to dry
What is recrystallisation used for?
To remove impurities from a solid after filtration
What are the steps for recrystallisation?
Warm chosen solvent
Add solvent to impure solid until dissolved
Cool to allow crystals to form
Filter crystals under reduced pressure
What is melting range and what indicates purity?
The temperature range a compound melts over. A pure compound melts sharply (1-2°C range), while impure samples melt lower and over a wider range
Why is melting point determination carried out?
To check purity of a compound
How is melting point measured with electrically heated apparatus?
Insert tube and thermometer
Rapid heat to approach mpt
Slow heating to get accurate temp
Record start and end of melting
How do you prepare a capillary tube for melting point testing?
Seal one end by rotating in a Bunsen flame
Cool and fill with dry, powdered sample
How is melting point measured using oil or Thiele tube?
Set up with oil and thermometer
Clamp thermometer and capillary so tip is in oil
Heat slowly with micro burner
Record mpt and repeat for accuracy
What is a target molecule?
The desired compound you are trying to synthesize
