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Preparing artificial fragrances and flavours
To prepare several esters that are widely used as artificial fragrances and flavours
· Small volumes of alkanols pentan-1-ol, methanol and ethanol
· Small amounts of various carboxylic acids: actanoic acid, glacial ethanoic acid and decanoic acid
· Salicylic acid
· Dropping bottle of sulfuric acid
· 6 x semi-micro test racks
· Small tongs
· 250mL beaker containing 100mL of boiling water
· 2 x 250mL beakers
· Marking pen
· Safety glasses
STEP 1 Label 2 semi-micro test-tubes ‘A’ and ‘B’. Place 10 drops of pentan-1-ol in each tube
STEP 2 Wearing gloves, add 10 drops of glacial ethanoic acid to test-tube A and a similar volume of salicylic acid to test tube B. Then add two drops of concentrated sulphuric acid to each tube
STEP 3 Heat the mixtures for 10minutes in a beaker of boiling water and then pour each one into a 250mL beaker containing 200mL of cold water
STEP 4 Try to identify the odour of the esters produced by wafting the vapour form the ester towards you. Note the name of the carboxylic acid and alkanol used in this test and describe the smell.
STEP 5 Wash the beakers thoroughly and repeat steps 1-4
In reaction 1 - Salicylic acid and Methanol were mixed
In reaction 2 - Acetic acid and Ethanol were mixed
Both reactions smelt like nail polish remover
Q1. Salicylic acid has the formula C6H4(OH)COOH. Write an equation for the reaction between methanol and salicylic acid.
C6H4(OH)COOH(l) + CH3OH (l) à C8H8O3 (l) + H20 (l)
Q2. Write the equations for each of the other reactions you performed in this experiment
CH3COOH (l) + CH3CH2OH à CH3COOCH2CH3 +H20
Acetic acid Ethanol
Q3. Name the esters that you have made in this experiment
The ester made in question one is methyl salicylate, and ethyl acetate was made in question 2
Q4. What is the role of the concentrated sulfuric acid in these reactions?
Esterification of carboxylic acids are slow in absence of a catalyst because they are not so reactive. Therefore sulfuric acid is added to speed up the chemical process. High yields of water are unfavourable, and because Sulfuric acid acts as a dehydrating agent, it will minimise the yield of water produced.
In this experiment of manufacturing artificial fragrances and flavours, the experimenters were not able to produce a pleasant smell. Possible discrepancies include statistical errors such as mixing incorrect mole ratios of carboxylic acid and alkanols. Or can be a systematic error such as the chemicals purchased from manufacturers were not in its correct form, may contain impurities that may affect the reaction to produce esters.
Good riddance VCE is over! My name is Daphane Ng, and I finished VCE in 2011! I studied English, Japanese SL, Psychology, Chemistry (yuk!), Biology and Methods. I'm hoping to do a Bachelor of Science at the University of Melbourne and later do a DipEd to become a science teacher in the future. I hope my resources help you achieve the ATAR you deserve. Best of luck!
Posted on 05/11/2016 at 12:00:00 AM