Misc. Exam Questions Flashcards
Summarise a method of organic purification (7)
- dissolve crude product in HOT solvent
- of MINIMUM volume
- filter to remove insoluble impurities
- cool to recrystallise
- filter under reduced pressure [with buchner/ hirsch apparatus]
- wash with cold solvent
- dry
Why may an electric heater be used rather than a bunsen burner?
- many organic compounds are flammable
State why reflux may be used in a practical?
- doesn’t allow reactant vapour to escape
Give the conditions for hydrogenation.
- H2 present
- Ni [catalyst]
Reagents required to synthesise nitriles from aldehydes
- KCN
- acid
Describe the apparatus used to remove the drying agent (any insolube solid really) by filtration under reduced pressure
- buchner funnel containing filter paper
- buchner flask connected to vacuum pump
Describe a method of determining melting point of a sample
- sample in suitable melting point apparatus (Thiele tube/ melting point apparatus/ capillary in oil bath)
- heat GRADUALLY
- lower melting point/ broad range of melting point indicates an impure sample
Explain the bonding in benzene
- each C has 3 covalent bonds
- spare electrons in P orbitals overlap (to form [Pi] cloud)
- delocalisation of electrons occurs
Explain the shape of benzene
- planar
- hexagonal ring w 120* bond angles
- C-C bonds are all equal lengths (between those of C-C and C=C)
What would be observed when an alcohol reacts with an acyl chloride
- misty/steamy fumes
Name the mechanism causing a ketone/aldehyde to be reduced to an alcohol (w NaBH4)
- nucleophillic addition
State why it’s better to form primary amines from nitriles rather than halogenoalkanes with ammonia
- (w haloalkanes) further reactions can occur so there’s an impure mixture/ lower atom economy
- (w nitriles) no further reaction so single product formed
Which products are formed when magnesium reacts with steam?
- Magnesium oxide
- hydrogen
Which amines are strongest in terms of base strength?
- tertiary
- secondary
- primary
- ammonia
- aromatic amines
