ch.28 organic synthesis

reacting haloalkanes with sodium cyanide NaCN or potassium cyanide KCN in ethanol nucleophilic substitution forming a nitrile

will react with hydrogen cyanide HCN in a nucleophilic addition reaction forming a hydroxynitrile HCN is too poisonous tho so NaCN and H2SO4 is used instead and increases rate of reaction due to the presence of the CN- ions

separating a solid product from a solvent or liquid

Buchner flask buchner funnel pressure tubing filter paper filter or vacuum pump

connect one end of tubing to vacuum and other end to Buchner flask fit Buchner flask funner to Buchner flask using a rubber bung to insure a seal turn on vacuum and test for suction by placing hand above funnel place filer paper in funnel wet with same solvent used in preparing the solid slowly pour reaction mixture into centre of filter paper rinse out beaker with solvent rinse crystals in funnel with more solvent the leave under vacuum for a couple of minutes to dry

solids after filtration will contain impurities recrystallisation removes these impurities

pour chosen solvent into conical flask if solvent is flammable warm with water bath if not bunsen burner add solid to another conical flask or beaker slowly add solvent to the impure sample adding minimum amount to dissolve allow to cool crystals should reform filter under reduced pressure to obtain dry crystalline solid

pure organic substances have a sharp melting range melting range is the difference in temp at which the sample starts to melt and the temp at which it has finished melting impure samples have lower melting points

sample must be completely dry hold one end of a glass capillary tube or meltinng point tube and rotate until end of tube is sealed allow tube to cool push open end of tube into sample to fill tube

place sample tube into sample hole and 0-300*C thermometer into thermometer hole using rapid heating setting start to heat up sample whilst observing. through window once seen to melt record temp allow apparatus to cool prepare second sample and reheat this time when approaching rough melting point set to low and slowly increase temp to find an acurate melting point

set up apparatus attach capillary tube to thermometer using rubber band insert thermometer through cork hole for thiele tube or clamp thermometer if using oil bath end of tube and thermometer should dip into oil use micro burner to slowly heat side arm of thiele tube or oil bath observe sample remove from heat when starts to melt record temp when fully melted make sure to heat oil gently and take multiple reading to insure accuracy