Chapter 28 - Organic Synthesis Flashcards
What is the functional group of a nitrile?
-CN
What are the two ways to form a nitrile?
- from a haloalkane
- from aldehydes/ketones
How can you prepare a nitrile from a haloalkane?
React haloalkane with sodium cyanide (NaCN) or potassium cyanide (KCN) in ethanol. Increases carbon chain length. NUCLEOPHILIC SUB
How can you prepare a nitrile from an aldehyde or a ketone?
React aldehyde/ketone with a mixture of sodium cyanide and sulfuric acid. Reduces alcohol group and increases carbon chain length. NUCLEOPHILIC ADDITION
What are the reagents, conditions and products of reduction of nitriles?
Reagent = hydrogen gas
Conditions = nickel catalyst
Product = amine
What are the reagents, conditions and products of hydrolysis of nitriles?
Reagents = dilute aqueous acid
Conditions = heat
Products = carboxylic acids and ammonium salt
What are the reagents, conditions and products of alkylation of benzene?
Reagents = haloalkane and benzene, halogen carrier
Conditions = n/a
Products = alkyl group attached to benzene ring
What are the reagents, conditions and products of acylation of benzene?
Reagents = acyl chloride, benzene, halogen carrier
Conditions = n/a
Products = ketone attached to benzene ring
What apparatus is required for filtration under reduced pressure?
- Buchner flask
- Buchner funnel
- pressure tubing
- filter paper
- access to filter or vacuum pump
How do you carry out filtration under reduced pressure?
- connect one end of pressure tubing to vacuum outlet or to filter pump, attach other end of tubing to Buchner flask
- fit Buchner funnel to Buchner flask, ensuring a good tight fit (rubber bung or Buchner ring)
- Switch on vacuum pump, or tap for filter pump
- check for good suction
- place a piece of filter paper inside the Buchner funnel and wet this with the same solvent used in preparing solid
- slowly pour reaction mixture from a beaker into the centre of the filter paper to filter
- rinse out beaker with solvent so all of solid crystals collect in Buchner funnel
- rinse crystal with more solvent and leave under suction for a few minutes so crystals start to dry
What is the purpose of recrystallisation?
To remove impurities from a solid product obtained after filtration
How do you carry out recrystallisation?
- pour chosen solvent into conical flask (if flammable = warm in water bath, if water = warm over Bunsen)
- tip impure sample into a second conical flask
- slowly add solvent to impure sample until it dissolves (you want minimum volume of solvent to do so)
- once solid dissolved, allow solution to cool, crystals should form
- when no more crystals form, filter under reduced pressure to obtain dry crystalline solid
How can you prepare a sample in a capillary tube for melting point determination?
- ensure sample is dry and free flowing
- take glass capillary tube and hold one end in hot flame of Bunsen, rotate until the end of the tube is sealed
- allow tube to cool, then fill with crystals by pushing open end into solid sample
How do you use electrically heating melting point apparatus to determine melting point?
- place capillary tube containing sample into sample hole, and a 0-300 degrees C thermometer in the thermometer hole of the melting point apparatus
- use rapid heat setting, start to heat sample whilst observing through magnifying window
- when solid is seen to melt, record melting point
- prepare second sample and again heat sample, but approach the melting point more slowly whilst observing the sample, so a more accurate determination can be observed
How can you use an oil bath or Thiele tube to determine melting point?
- set up oil bath or Thiele tube
- attach capillary tube with sample to a thermometer using a rubber band
- insert thermometer through a hole in cork (Thiele tube) or clamp thermometer (oil bath). The end of the thermometer and end of the capillary tube should dip into oil
- using a micro burner, slowly heat side arm of Thiele tube or oil bath while observing solid
- when solid starts to melt, remove heat and record temperature at which all of solid has melted
- repeat a second time, ensure both times oil is melted slowly
