chapter 28 Flashcards
formation of nitriles from haloalkanes
reacting haloalkanes w/ sodium cyanide NaCN or potassium cyanide KCN, in ethanol
length of carbon chain increased
CH3CH2CH2Cl + KCN –> CH3CH2CH2CN + KCl
formation of nitriles from aldehydes and ketones
react w/ hydrogen cyanide in a nucleophillic addition reaction
CH3COCH3 + HCN –> CH3C(OH)(CN)CH3
product- hydroxynitrile
Hydrogen cyanide- too poisonous, mix of sodium cyanide and sulfuric acid is used
reduction of nitriles
can be reduced to amines by reacting w/ hydrogen in presence of a nickel catalyst
CH3CH2CN +2H2–Ni catalyst—> CH3CH2CH2NH2
propanenitrile propylamine
hydrolysis of nitriles
form carboxylic acids by heating w/ aq acid eg HCl
CH3CH2CH2CN + 2H2O + HCl –heat—> CH3CH2CH2COOH + NH4Cl
butanenitrile- butanoic acid
alkylation of benzene
transfers an alkyl group from a haloalkane to a benzene ring
Freidel-Crafts catalyst eg aluminium chloride
eg methylation of benzene
C6H5 + C2H5Cl —AlCl3—> ethyl benzene + HCl
acylation of benzene
benzene reacts w/ an acyl chloride in the presence of an aluminium chloride catalyst- ketone formed
C6H6 + C2H5COCl —AlCl3—> phenylpropanone + HCl
filtration under reduced pressure
technique for separating a solid product from a solvent/liquid reaction mix -Buchner flask. -pressure tubing -Buchner funnel. -filter paper -access to filter or vacuum pump
1) connect 1 end of tubing to vacuum outlet/filter pump and the other to the buchner flask
2) fit the funnel to the flask- tight fit obtained w/ rubber bung
3) switch on vacuum pump, or tap
4) check for good suction by placing hand across top of funnel
5) place filter paper inside funnel and wet w/ same solvent used to prepare solid
6) pour reaction mix into centre of filter paper
7) rinse out beaker w/ solvent so solid crystals collect in funnel
8) rinse crystals in funnel w/ more solvent and leave them under suction so crystals dry
recrystallisation
removes impurities
1) pour chosen solvent into a conical flask, if flammable warm over a water bath. if it is water, place con gauze above bunsen & warm
2) tip impure sample into second flask/beaker
3) slowly add solvent to impure sample until it dissolves- add min vol
4) once dissolved, allow to cool, crystals should form of desired product. when no more crystals from filter under reduced pressure to obtain dry crystalline solid
melting point determination
has to be pure, impure has lower melting point
1) ensure sample is dry & free flowing
2) take a glass capillary tuba and hold end in bunsen. rotate until end is sealed
3) cool then fill w/ crystals about 3mm deep
4) taken 2 diff ways
mp w/ electronic mp apparatus
1) place capillary tube into sample whole & thermometer in apparatus
2) use rapid heating setting and observe through window
3) when melts record mp, then allow apparatus to cool
4) prepare second sample & repeat
5) as mp is reached set to slow & raise temp slowly
mp w/ oil bath or Thiele tube method
1) set up
2) Attach capillary tube containing sample to thermometer using a rubber band
3) insert thermometer through hole in cork w/ Thiele tube or clamp using a oil bath- end should dip into oil
4) using a micro burner, slowly heat side arm of Thiele tube whilst observing solid, when starts to melt remove heat & record temp. repeat for accurate results.
