55058 chemistry basic laboratory ii (organic chemistry) .55058 chemistry basic laboratory ii...
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Chemistry basic laboratory II
Organic chemistry laboratory
Department of Chemistry
University of Helsinki 2016
Glassware etc. 6
Working practices 10 How to perform a reaction 10 Heating reaction mixture 10 Mechanical stirring 11 Isolation 12 Suction filtration 12 Extraction 12 Purification 13 Recrystallization 13 Distillation 14 Sublimation 18 Chromatography 19 Synthesis reports 21Synthesis 25
meso-1,2-Dibromo-1,2-diphenyl ethane 25 Acetyl salicylic acid 26 Ethyl propionate 27 Benzoin 28 Reduction of benzoin with NaBH4 29
p-Methyl acetophenone 30p-Benzoquinone 31
Location: Room B147 and B151 (First floor wing B in Chemicum)Instructors' room telephone number 02941 50426
The laboratory hours 8.30 - 16.45 daily. The laboratory period lasts 2 weeks.
You must be present on the first day of the course at 8.30 o'clock when the work benches areallocated. You must check the contents of bench drawers according to the list given by thetechnician. When you are finished you must check out your glassware (with the laboratorytechnician, see the main stockroom) by the last day of the course. If you fail to do the checking-outyou will be required to pay 40 fine.
Please print the course material before you come to the laboratory. Mandatory absence due toexams etc. must be agreed with the teacher of the group in advance. The synthesis form and theproduct should be given to the teacher for checking as soon as possible.
The course Chemistry basic laboratory II contains seven synthesis. The theory (reaction mechanism)and the execution as well as the safety matters of the laboratory work is examined in the morninggroup wise led by the assistant. It is therefore important to be present right from the start of thework session. The participants of the course will be divided into groups in such a way, that everygroup works on a different synthesis. The members of the group carry out the same synthesisindividually. The student receives a grade for the four last synthesis. The grade is based on theproduct yield and purity.
During the synthetic lab work a test on work methods and laboratory safety will be held, whichconsists of questions related to safety at work.
Follow the safety regulations: wear safe glasses at all times, no fire in the lab etc. Keep your workingarea clean.
For the course you need lab coat notebook
Essential safety rulesCheck the location of: exit routes fire-extinguishers fire-blankets and safety showers waste containers Find out the properties of the chemicals you are handling
Always:Handle all chemicals with great careKeep you working area cleanAttend to spills immediately
Never:Eat or drink in the laboratory
Always wear eye protection, gloves and laboratory coat in the laboratory
All experiments must be done in fume hoods
Fire safety flammable liquids: ether, acetone, petroleum ether etc. danger of fire, danger of explosion, fire-fighting equipment electrical safety how to handle electrical equipments safely
Apparatus Never heat a closed apparatus When heating use stirring or boiling stones. Dont heat the oil bath over 200C, use thermometerin oil bath
dont use flame for heating dont evaporate solvents from open vessels.
Waste handle and dishwashingNever pour water immiscible organic solvents down the sinkWaste solvent should be poured into appropriately labelled containersWater soluble waste like discarded water layers from aqueous-organic extractions, ethanol,neutralized acids and bases can be poured down the sinkUse acetone to rinse your glassware
Hazardous chemicals Corrosive reagents: strong acids and bases, oxidizing, reducing, and explosive chemicals andcarcinogens. Br2, Na, AlCl3, KCN, NaOH, KOH, LiAlH4, H2, NaBH4, KBrO3, SOCl2, Hg Aniline, methanol, phenol, chloroform, methyl iodide, isoforone Sodium hypochlorite, H2O2, benzoylperoxide, silica dust.Br2 can be neutralized with Na2CO3 (aq) and ethanol Cyanides can be neutralized by oxidation. Under basic conditions cyanide ion oxidizes for examplewith sodium hypochlorite first to cyanate (OCN-) and further to nitrogen gas and carbon dioxide.
Glassware withconical joints
erlenmeyer (29/32) erlenmeyer (14/23)
round bottom flask (29/32)
round bottom flask (14/23)
pear shaped flask
Glassware without conical joints
adapter 29 to 14
mortar andpestle evaporation dish
suction flask andits stopper
glass dish watchglass
test tubes andrack
magnetic stirrer steel pan (oil bath)
plastic tubewashing bottle
WORKING PRACTICESHow to perform a reaction
Heating reaction mixturesHeating reaction mixtures (reflux), recrystallization etc. is done with the apparatus on the followingpicture. The condenser prevents the evaporation of the liquid during the heating. In the condenserthe solvent vapours condense into a liquid and the liquid returns into the flask. To prevent overheating the mixture must be stirred or 1-2 boiling stones should be added into the mixture. If theboiling point of the heated liquid is under 80 C the water bath is used for heating. In case the boilingpoint of the liquid is higher silicon oil bath is used. Use thermometer in an oil bath. Never heat anoil bath over 200 C. Avoid getting water in the oil bath because it causes splashing of the hot oil.Never use closed apparatus for heating because closed system may explode.
Mechanical stirringIf the reaction mixture is stiff mechanical stirring is used for the efficient stirring for example inFriedel-Crafs reaction. Fix the stirrer firmly to the support stand. Cautiously test run the emptyapparatus before adding the starting materials.Note! If you use a dropping funnel with a bypass use a stopper instead of CaCl2 tubing.
Apparatus for Friedel-Crafts reaction (p-Methyl acetophenone)
When solid material is isolated from the reaction mixture (like product precipitates from thereaction mixture) the suction filtration is used (see the apparatus above). Both suction flasks areconnect to the support stands with clamps. In the Bchner funnel a filter paper of correct size shouldbe used. The paper should not turn up the edges of the Bchner funnel. Moisten the filter paperwith the same solvent which forms the filtrate. Turn the water aspirator tab on completely and closethe suction flask stopper and start filtering. When the filtration is switched off first release thenormal pressure into the apparatus by opening the suction flask stopper. When drying agent isremoved from the solvent use glass funnel with a small amount of cotton wool.
ExtractionIn order to move the reaction product from the water solution into the organic solvent the watersolution is shaken with organic solvent e.g. ether in an extraction funnel.
A separatory funnel is usually made of thin glass and it should be handled carefully. The stopcock ofthe separatory funnel is either glass or Teflon. Glass stopcock should be lightly greased before useso that it turns easily. Support the separatory funnel in a metal ring clamped to a stand. Get into thehabit of placing an Erlenmeyer or beaker under the separatory funnel as soon as you put it in itsring. Check that the stopper fits well for the glass joint. With the stopcock closed (check!) pour the
stopper for suction flask
thick wall tubing
mixture to be extracted and the extraction solvent into the separatory funnel. As a general rule,never fill the separatory funnel more than two-thirds full.
To carry out the extraction, the aqueous and organic layers have to be thoroughly mixed. Afteradding the liquids to the funnel, and before inserting the stopper, it is good idea initially to swirl theseparatory funnel gently. This swirling causes some preliminary mixing of the layers, and isparticularly important when aqueous carbonate or bicarbonate is being used to extract or neutralizeacidic components. Preliminary swirling will reduce the problems from excessive pressure buildingup during the extraction. After swirling insert the stopper. More vigorous shaking is needed to mixthe layers. For holding a separatory funnel the following method is recommended (see the picturebelow). Hold the funnel with both hands. Hold the stopper with one hand and hold the funnelaround stopcock with the other hand, so that you van open the stopcock quickly with your fingers.If doubt, practise your grip with an empty funnel.
To carry out the extraction, lift the separatory funnel of its