synthesis and characterization of ASA

Question 1

what does the synthesis involve

Answer 1

the reaction of salicylic acid and acetic anhydride in presence of catalyst (phosphoric acid H3PO4)

Question 2

what was salicylic acid derived from

Answer 2

bark of white willow tree

Question 3

what is the reaction equation for ASA

Answer 3

Question 4

is aspirin soluble in water

Answer 4

yes, cold water

Question 5

how can aspirin be isolated

Answer 5

by filtering the chilled reaction solution

Question 6

why is purification necessary

Answer 6

to remove any unwanted salicylic acid
acetic anhydride
acetic product
acid catalyze

Question 7

how does acetic anhydride decompose

Answer 7

by the addition of water once formation of aspirin is complete

Question 8

how can the acetic acid and sulfuric acid be removed from the product

Answer 8

they are water soluble so washing the aspirin with chilled water will remove these ions

Question 9

what is NOT removed in the wash with chilled water

Answer 9

salicylic acid - not soluble in water

Question 10

how is FINAL purification done

Answer 10

by recrystallization

Question 11

how is salicylic acid removed from aspirin crystals

Answer 11

impure aspirin dissolved in warm ethanol before cooled slowly and aspirin crystalizes out of solution leaving salicylic acid and other impurities behind

Question 12

what on the IR indicates success

Answer 12

disappearance of hydroxyl group and presence of ester

Question 13

what on the IR indicates failur

Answer 13

presence of hydroxyl group and absence of ester

Question 14

functional groups in acetylsalicylic acid

Answer 14

C=O-OC - Ester

C=O-OH = carboxylic

ring = aromatic carbon

Question 15

what product forms when acetic anhydride reacts with water

Answer 15

acetic acid

Question 16

balanced equation for acetic anhydride with water

Answer 16

C4H6O3 + H2O —-> 2 CH3COOH

Question 17

functional groups in salicylic acid

Answer 17

C-O-H = alcohol

C=O -O-H = carboxylic acid

Question 18

safety considerations of acetic anhydride and sulfuric acid

Answer 18

bad burns and MUST be used in fume hood

Question 19

how can excess chemicals be disposed of

Answer 19

down the sink with lots of water BECAUSE the acetic anhydride will convert to vinegar

Question 20

how much salicylic acid was weighed

Answer 20

3 grams and put in an Erlenmeyer flask

Question 21

what was added to the flask with salylic acid

Answer 21

• 6 ml of acetic anhydride
• 5 to 10 drops of 18 M H2SO4

Question 22

what was done with the Erlenmeyer flask after adding all the regents

Answer 22

heat for 10 mins in water bath

Question 23

what is done with the flask after heating

Answer 23

add 20 drops of RO water AFTER add 20 ml before cooling in ice bath

Question 24

after the solution is cooled in ice bath, what is done

Answer 24

filter solid iron through filter paper using buchner funnel

Question 25

describe the FIRST wash for the solid product with a Buchner funnel

Answer 25

1. first wash with 5 ml chilled water after let air draw through for 15 mins

Question 26

what is done with the impure aspirin after drawing air through and weighed

Answer 26

1. transfer to 150 ml beaker and add 10 ml 95% ethanol and warm the beaker till dissolved 2. after all crystals dissolved add 20 ml of warm water and cover with watch glass to let cool

Question 27

how is recrystallization completed

Answer 27

by cooling solution in ice bath

Question 28

how is the purified crystals collected

Answer 28

1. filtration with the Buchner funnel again 2. wash with 5 ml cool water 3. draw air through for 15 mins

Question 29

when does stretching frequency increase

Answer 29

as bond strength increases

Question 30

what has the lowest stretching frequency, what has the highest?

Answer 30

lowest = single bond (lowest strength) highest = triple bond (highest strength)

Question 31

what does a larger mass between atoms in a bond mean for stretching frequency

Answer 31

they would vibrate at a LOWER frequency compared to lighter atoms

Question 32

can molecules occupy any vibrational levels

Answer 32

NO - only specific ones

Question 33

can a bond be non-polar to be absorbed ( to exhibit changes in dipole)

Answer 33

NO - must be POLAR

Question 34

what determines the amount of energy a molecule can absorb

Answer 34

1. bond strength 2. masses of atoms 3. polar

Question 35

what frequency of light will be absorbed by a molecule

Answer 35

only those frequencies that match vibrational energy level differences