This activity is divided into three parts. The morning is designed to give studentsthe opportunity to prepare and purify a sample by the dehydration of cyclohexanol.In the afternoon session students use analytical instruments to analyse their product.The plenary session involves a detailed explanation of the results.
materials required
Part A/B: Primarydistillation andseparation• gloves• cyclohexanol 25 cm3
and stopper• small funnel• 2 x 100 cm3 conical flasks• stopper for conical flask
pre-planning required
weeks before• Plan with schools how many students are coming to the session.• A good time to hold sessions is during the Easter break or after summer exams.• Book rooms, refreshments, staff, equipment/instruments and inform technicians
and ensure chemicals and sufficient safety glasses and lab coats are in stock.
days beforeTrain demonstrators to do the practical and the associated safety aspects. Ask technicians to prepare kits of apparatus and chemicals and to set out workstations in the fume cupboards the day before.
facilities required
• A suitable laboratory for the preparative work with one fume cupboard per studentif they are working individually. For larger numbers or younger students it may bebetter to work in pairs.
• Access to NMR, FTIR, GCMS for the afternoon session.• Tutorial room or lecture theatre for introduction and plenary session.
(Quickfit® No. B14)• condenser• receiver adapter• three sample tubes• cork ring• three clips (Quickfit®
No. B14)• labels
Suggested timings for the day
09.15 Arrival, registration and refreshments09.30 Welcome and introduction. Explanation of the morning’s practical and safety advice09.50 Laboratory session12.30 Lunch13.30 Instrumentation introduction13.35 Spectroscopic analysis of samples (three groups, 30 mins per technique, rotating)
15.20 Plenary discussions, conclusions, highlighting significant features for each spectraobtained and refreshments
16.00 Depart
time/group 13.35-14.10 14.10-14.45 14.45-15.20
A IR NMR GCMS
B NMR GCMS IR
C GCMS IR NMR
extension activities for gifted and talented
Ask what happens if bromine water is added to the product. Demonstrate theresult if time permits.
general equipment
• clamp, retort stands and rings• NMR spectrometer• GCMS• IR Spectrometer
• sodium chloride IR plates• NMR tubes• CDCl3 with TMS NMR solvent
NOTE
It is useful to have a fulldistillation set up of the glassware on displayin the lab for the students to refer to at thestart of the practical.
Part A: Primary distillation – Reaction of cyclohexanol (in a fume cupboard)
Set up the apparatus as shown in thediagram with a 100 cm3 distillation flask.
Using a 25 cm3 measuring cylindermeasure 25 cm3 of cyclohexanol andpour it through a funnel into thedistillation flask.
Using a 10 cm3 measuring cylinder add10 cm3 of concentrated phosphoric acid(85%) to the flask. (Safety note:corrosive, gloves must be worn).
Add a small heaped spatula ofantibumping granules and then heatgently using a heating mantle.
A mixture of reaction product and watershould distil over at a rate of about 2 cm3
per minute. The temperature reading onthe thermometer should not be allowed torise above 105 oC.
Stop the distillation when 20 cm3 ofdistillate have been collected.
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aim
You are supplied with a sample of cyclohexanol and are expected to do a reactionusing the distillation apparatus and chemicals provided. The product should thenbe purified ready for instrumental analysis and identification.
SAFETY
Ask the demonstrator to checkthe apparatus is correctly set up. Ensure thewater is flowing through the condenser. No naked flames – flammable product.
Assemble the retort stand, ring,separating funnel and conical flask as shown.
Close the tap. Using a funnel, pour inthe distillate from the reaction, and add5 cm3 of saturated sodium chloride (addthis using the distillate vessel to rinse outall of the product into the funnel).
Swirl the mixture and check excessiveCO2 is not being evolved as too muchgas makes the stopper blow off. Add the stopper.
Remove from the retort stand, invert,keeping your finger on the stopper andshake gently, releasing pressure byopening and closing the tap regularly.Do not shake too vigorously!
Place the funnel back in the stand andallow the layers to separate. Remove the stopper before step six.
Gently run off the aqueous lower layerinto a conical flask and set this aside.
Transfer the organic upper layer into aclean, dry conical flask and add twosmall spatulas of anhydrous calciumchloride and swirl.
Allow to stand for 15 mins whiledismantling the rest of your distillationapparatus if it has cooled sufficiently.
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SAFETY
Always point the stem of theseparating funnel away from yourself andothers during venting, keep your finger onthe stopper at all times.
