practical final work

8/13/2019 Practical Final Work

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37th International Chemistry Olympiad

Taipei, Taiwan

Practical ExaminationTuesday, 19 July !!"

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Important #emar$s

The plastic bag you got upon entering the laboratory is the unknown samples for experiment2. Put it inside the basket on your bench for later use.

At all times while you are in the laboratory you should wear safety spectacles or your own

spectacles if they have been approved.

Eating of any kind of food is strictly prohibited in the laboratory.

When you enter the laboratory check the place of the safety shower.

Participants are expected to work safely to behave socially and to keep e!uipment and work

environment clean. "o not hesitate to ask a laboratory assistant if you have any !uestions

concerning safety issues.

%or$ may only &e'in when the start si'nal is 'i(en)

#ou have $ hours to complete all of the experimental tasks and record your results on the

answer sheets. There will be a pre%warning &' minutes before the end of your time. #ou must

stop your work immediately after the stop command is given. A delay in doing this by $

minutes will lead to cancellation of the current task and will result in (ero points for that task.

This practical examination comprises two experiments) In order to use the a(aila&le

time e**iciently, you will start wor$in' on the or'anic chemistry experiment up to the

point where you are instructed to wor$ on the analytical chemistry experiment) Then

you will *inish the wor$ on the or'anic chemistry experiment) The second part o* the

or'anic experiment +experiment 1 will need at least 1 hour)

-se only the pen and calculator pro(ided)

Write your name and personal identification code )in the back of your name card* on every

answer sheets.

All results must be written in the answer boxes on the answer sheets. "ata written elsewhere

will not be marked. "o not write anything in the back of your answer sheets. +f you need more

paper for working or a replacement answer sheet re!uest it from the laboratory assistant.

When you have finished the examination you must put all answer sheets into the envelope

provided. ,nly papers in the envelope will be marked.

"o not leave the examination room until you have permission to do so.

-se only the tools provided.

There are total " pages of answer sheets . for organic and 1 for analytical experiment

respectively.

blank draft papers )will not be marked* are provided more are available on re!uest

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An official English%language version is available only on re!uest.

/isposal o* waste chemicals, spills, and 'lassware

There are three waste containers in the lab one for organic filtrates and organic washings one for

solid wastes and one for broken glass.

Cleanin' up

Please keep your work area clean. Wipe your lab bench with a wet tissue when you are finished.

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Or'anic synthesis

Equipment list

e!uipment /o. e!uipment /o.

0ot plate1stirrer with stand Weighing paper '

3tirrer 2 3ample vial )2' m4*

(blue label labelled with your

student code and 1H NMR)

3tirrer retriever 3hared by

2 persons

3ample vial )2' m4*

(pink label labelled with your

student code and [α]D)

5iltration pump 3hared by

2 persons

6lass rod

7lamp with holder & 3patula 2

thermometer 3epta 2

Pasteur pipette $ Water bath )stainless steel*

Pipette bulb 2 +ce bath )3tyrofoam*

6raduated cylinder )' m4* /eedle

6raduated cylinder)2$ m4* Water bottle with "eioni(ed 02,

8ound bottom flask )2$ m4* 6love )cotton* pair

8ound bottom flask )$' m4* 6love )latex* on central bench

5ilter 5ritted )$' m4*

(labelled with your student code)

5lask holder pc

5ilter 5ritted )9' m4*

(labelled with your student code)

Paper towel roll

5iltration flask with rubber )2$' m4* :imwipes box

7ondenser 6lass funnel

Teflon sleeve for condenser

(you can trim off 1 cm from the smaller

end for a better fit)

;eaker )<'' m4*

3afety goggles ;eaker )'' m4*

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8isk statements

8 0ighly flammable.

8 2' 0armful by inhalation.

8 22 0armful if swallowed.

8 2$ Toxic if swallowed.

8 & 7ontact with acids liberates toxic gas.

8 &2 7ontact with acid liberates very toxic gas.

8 & 7auses burns.

8 &$ 7auses severe burns.

8 &= +rritating to eyes.

8 &9 +rritating to respiratory system.

8 &< +rritating to skin.

8 ' 4imited evidence of a carcinogenic effect

8 8isk of serious damage to the eyes.

8 & Cay cause sensiti(ation by skin contact.

8 $' Dery toxic to a!uatic organisms.

8 $2 0armful to a!uatic organisms.

8 $& Cay cause long%term adverse effects in the a!uatic environment.

7ombination of risk statements

8 2'12122 0armful by inhalation in contact with skin and if swallowed.

8 &=1&91&< +rritating to eyes respiratory system and skin.

3afety statements

3 9 :eep container tightly closed.

3 & :eep away from food drink and animal foodstuffs.

3 = :eep away from sources of ignition % /o smoking.

3 22 "o not breathe dust.

3 2& "o not breathe gas1fumes1vapour1spray )appropriate wording to be specified by the

manufacturer*.

3 2&.2 "o not breathe vapor.

3 2 Avoid contact with skin.

3 2= +n case of contact with eyes rinse immediately with plenty of water and seek medical

advice.

3 2< After contact with skin wash immediately with plenty of soap%suds.

3 &' /ever add water to this product.

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3 &= Wear suitable protective clothing.

3 &9 Wear suitable gloves.

3&? Wear eye 1 face protection.

3 +n case of fire and1or explosion do not breathe fumes.

3 $ +n case of accident or if you feel unwell seek medical advice immediately )show the label

where possible*.

3 =' This material and its container must be disposed of as ha(ardous waste.

3 = Avoid release to the environment. 8efer to special instructions 1 3afety data sheets.

7ombination of safety statements

3 212$ Avoid contact with skin and eyes.

3 &=1&91&? Wear suitable protective clothing gloves and eye1face protection.

3 &=1&9 Wear suitable protective clothing and gloves.

3 &91&? Wear suitable gloves and eye1face protection.

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Experiment 1

The 0ynthesis o* /,2Phenyl'lycine and Its Enantiomeric #esolution

,ne of the enantiomeric forms of phenylglycine is an important raw material for the preparation

of β%lactam antibiotics. +ndustrial production of optically active phenylglycine is prepared by the

Andeno process. The starting ben(aldehyde was treated with 07/1/0& following hydrolysis to give

the racemic "4%phenylglycine. The desired enantiomeric phenylglycine was then resolved by )B*%

camphorsulfonic acid @)B*%73A.

#

#

#H70,

1$ H%N& NH32$ Hydrolysis

D&'henyl*lycine

Rh catalystH%##NH4

(+ndeno rocess)

;en(aldehyde "4%phenylglycine ;en(oylformic acid

+n this experiment you are going to synthesi(e racemic "4%phenylglycine )also referred to as

8% and 3% isomers respectively* from an alternative method called reductive amination. Treatment

of ben(oylformic acid under 8h metal cataly(ed conditions gives "4%phenylglycine. The racemic

"4%phenylglycine is resolved by the treatment of )B*%73A in water. The solubility of "%

phenylglycine•)B*%73A salt is $.9$ g1''g 02, while that of 4%phenylglycine•)B*%73A salt is $'

g1''g 02, at 2$ F7. The chemical yield and the optical purity of the diastereomeric salt will be

measured.

EPE#I4E5T6 P#OCE/-#E

Caution 8ou ha(e to wear latex 'lo(es durin' all operation *or practical tas$ 1)

0tep 1) Preparation o* /,2phenyl'lycine

The following pre-weighted chemicals can be used directly without further weighing:

Benzoylformic Acid; Ammonium Formate; Rh Catalyst; !"-camphorsulfonic acid #!"-

C$A%&

. To a $' m4 round%bottomed flask is added a magnetic stirring bar pre%weighed )approximate

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.<' g exact mass will be on your sample bottle write down the mass on your answer sheet

and get the lab assistant to confirm the weight.* of ben(oylformic acid )5OTE irritant' do not

contact with s(in* 9.$9 g of ammonium formate )07,2/0* &9.2 mg of 8h catalyst )5OTEthe catalyst is wrapped in a wei'hin' paper in a plastic &a') andle with care:* and 22 m4

of the pre%mixed solvents at ambient temperature.

2. Put a reflux condenser )use the Teflon sleeveG you can trim off cm from the smaller end for a

better fit* into the neck of the flask and plug the condenser with a septum. 5or pressure

e!uilibration put a needle in the septum before starting the heating. 7lamp the apparatus

tightly to the stand in your hot plate1stirrer. Put the flask onto a hot water bath @hot water

provided by the organi(er and stir the reaction mixture gently. ) 5OTE the sol(ent is air

cooled, so there is no tap water runnin' throu'h the condenser) * The temperature of the

water bath needs to be maintained in the range of =< to 92 F7 by adHusting the thermostat of the

hot plate1stirrer.

&. The mixture will become cloudy and the color of the solution will change from clear yellowish to

dark%greenish when the product starts to precipitate )generally re!uiring 2$ I &$ minutes*. The

hot water bath should then be removed and the solution allowed to stir in the water bath

)ambient temperature* for an additional ' minutes.

. Add $ m4 of deioni(ed water to the resulting mixture and stir for ' minutes.

$. Pre%weigh the bigger fritted glass funnel )labelled with your student code* and get the lab

assistant to confirm the weight. -se the stir bar retriever to remove the stir bar. 7ollect the

product by filter suction through a fritted glass funnel under a reduced pressure )rotary aspirator

apparatus*. Wash the solid four times thoroughly with ethanol )' m4 each*. 5or each washing

brea( the aspirator pressure use a glass rod to perturb the solid when adding ethanol and

reapply the rotary aspirator.

=. 5or rapid drying you have to spread the product over the fritted glass funnel. 5or drying give

the fritted glass funnel to the lab assistant. The product is dried in the oven at '' F7 for .$

hour.

)uring the drying period you can start wor(ing on *+periment , Analytical

*+periment" and you will be notified when your product is ready& $tep , ofe+periment will need at least hour&

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9. Weigh the dried product @)"4*%phenylglycine record the data and calculate the chemical yield)based on the starting ben(oylformic acid*. 6et the lab assistant to confirm the weight. The

purity of the product will be determined by 0 /C8 spectrum analysis. Turn in the product in a

vial )&lue la&el with 0 /C8 and your student code* to the lab assistant and receive a new

batch of "4%phenylglycine for step 2.

0tep ) Enantiomeric resolution o* /,2phenyl'lycine &y +;2camphorsul*onic acid <+;2C06=

. To a 2$ m4 round%bottomed flask add the pre%weighed sample of "4%phenylglycine provided

)The exact mass will be on your sample bottle write down the mass on your answer sheet and

get the lab assistant to confirm the weight*. To this add the pre%weighed )B*%camphorsulfonic

acid @)B*%73A ).<' g*. 7lamp the apparatus tightly to a stand in a magnetic stirrer. Add

deioni(ed water ) m4* and place the flask in a hot water bath and heat it to a temperature in

the range of ?' I '' F7. :eep the mixture at this temperature for ' minutes until it turns

clear.

2. 8emove the hot water bath and allow the mixture to cool down to ambient temperature for

'I$ minutes. With the flask plugged with a septum cool the flask in ice bath )3tyroform* for

$ minutes. 7rystals should appear in about 2' minutes if not you may ask for seed crystals to

induce the crystalli(ation.

&. Pre%weigh the smaller fritted glass funnel )labelled with your student code* and get the lab

assistant to confirm the weight. 7ollect the product by filtering the solution through a fritted

glass funnel under a reduced pressure. Wash the solid thoroughly two times with ice cooled

distilled water )$ m4 each*.

. 5or drying give the fritted glass funnel to the lab assistant. The product will be dried over in

oven at '' F7 for 2' min. #ou will be notified when your product is ready. Weigh the product

and get the lab assistant to confirm the weight. 8ecord the data and calculate the chemical

yield )based on starting "4%phenylglycine*.

$. The optical purity of the diastereomeric salt will be measured using an accurate polarimeter

apparatus by the examination committee. Transfer the dried product to a sample vial )pin$la&el labelled with @α" and your student code* and give the sample vial to the lab assistant)

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The organi(ation committee will weigh an appropriate amount of the product )'.'$$ I '.'=$g*

for measurement of optical purity.

The organization committee will weigh the resolved product (from the fritted glass funnel) for

students who fail to finish the procedure in time. However, 1 penalty points will be ta!en.

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Experiment

Identi*ication o* -n$nown Inor'anic 0amples

5ote

)* This practical exercise is a kind of Jspot testK. #ou can do it on the pallet or on a sheet of black

film )for white precipitate*.

)2* Please check all items written in the e!uipment and reagent list.

)&* Please chec$ care*ully the code num&er o* the un$nown sample with the Chec$ ist

accompanied with your un$nown samples)

)* The volume of each unknown solution is about .$ m4 )about &' drops*. 5o more rea'ents or

samples will &e pro(ided.

)$* ;e sure to confirm your results before writing your answers in the blanks of the Answer 3heet.

)=* Cake sure the switch on the battery box is closed.

)9* 8ou will 'et > points *or each correct identi*ication)

Introduction

There are 2 unknown samples in your plastic bag：? unknown solutions are in droppers and

& unknown solids are in vials. All unknown samples are numbered with a & digit code. Please

check the number with the ist o* -n$nown Inor'anic 0amples carefully then write your student

code and name on the list. )The list is accompanied with your unknown samples* Each vial

contains about 2' mg of crystals or powder of one pure compound. Each dropper contains about

.$ m4 solution of one pure compound dissolved in distilled water. The concentration of unknown

solutions is in the range of '.'$ to '.$ C )mol14*.

The unknown samples are as follows>

07l 02,2 023, Ln7l2 /037/

/a,0 /a27,& /a23,& ;a7l2 :5e)7/*=

5ote

)* Two unknown samples are duplicates.

)2* The hydrated 02, of crystal is omitted in the formulas listed above.

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,n your lab bench there is a plastic basket which contains the e!uipments unknown

samples and reagents to be used in this task.

E!uipment list

e!uipment /o. e!uipment /o.

Pt wire electrode Au wire electrode

;attery case ;attery 2

Pallet ;lack film )round*

3cissors "ropper ) m4* $

7offee stirrer 2

8eagent list

8eagent 7onc. 8eagent 7onc.

:+ '.C pp )phenolphthalein* '.'％

5e7l& '.C 3tarch solution '.'％

8isk and safety statements

7hemicals 5ormula 8isk statements 3afety statements

0ydrochloric acid 07l &=1&91&< 2=

3ulfuric acid 023, &$ 2=%&'%$

3odium hydroxide solution /a,0 &$ 2=%&=1&91&?%$

0ydrogen peroxide solution 02,2 22% 2=%&?

3odium carbonate solution /a27,& &= 22%2=

;arium chloride solution ;a7l2 2'%2$ $

3odium sulfite solution /a23,& &%&=1&91&< 2=%&=

Linc chloride solution Ln7l2 22%&%$'1$& 2=%&=1&91&?%$%='%=

Potassium

hexacyanoferrate )++*

solution

:5e)7/*= &2 22%212$

Ammonium thiocyanate

solution

/037/ 2'12122%&2%$21$& &%=

+ron )+++* chloride )solid* 5e7l& 22%& 2=%&=1&91&?%$

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Potassium iodide )solid* :+ % 22%212$ M

3tarch solution % % %

Phenolphthalein indicator ' &=1&9

,- -se the four reagents provided and mutual reactions among the unknown samples and the

simple electrolysis apparatus to identify each unknown sample and write your answer )& digit

code* in the blanks of your answer sheet.

,-, +n this practical work you have performed a series of tests to identify )or confirm* the

unknowns. 3how the reactions involved by way of chemical e!uations.

A. Write the electrolysis e!uation that would help you confirm that an unknown sample is

Ln7l2.

;. Write one e!uation that shows how to clean the deposit of Ln on the electrode )limited to

the items provided in this task*.

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Note

+.ter you ha/e .inished your wor0& lease ut the two electrodes (t and +u wires) and two

batteries bac0 in their ori*inal lastic ba*s& resecti/ely& then return all euient and rea*ents

(include un0nown sales) to the ori*inal laces (in the lastic bas0et)$

practical final work

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