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Chemistry 2000 lab exam > synthesis and characterization of ASA > Flashcards

synthesis and characterization of ASA Flashcards

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1
Q

what does the synthesis involve

A

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

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2
Q

what was salicylic acid derived from

A

bark of white willow tree

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3
Q

what is the reaction equation for ASA

A
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4
Q

is aspirin soluble in water

A

yes, cold water

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5
Q

how can aspirin be isolated

A

by filtering the chilled reaction solution

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6
Q

why is purification necessary

A

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

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7
Q

how does acetic anhydride decompose

A

by the addition of water once formation of aspirin is complete

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8
Q

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

A

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

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9
Q

what is NOT removed in the wash with chilled water

A

salicylic acid - not soluble in water

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10
Q

how is FINAL purification done

A

by recrystallization

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11
Q

how is salicylic acid removed from aspirin crystals

A

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

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12
Q

what on the IR indicates success

A

disappearance of hydroxyl group and presence of ester

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13
Q

what on the IR indicates failur

A

presence of hydroxyl group and absence of ester

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14
Q

functional groups in acetylsalicylic acid

A

C=O-OC - Ester

C=O-OH = carboxylic

ring = aromatic carbon

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15
Q

what product forms when acetic anhydride reacts with water

A

acetic acid

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16
Q

balanced equation for acetic anhydride with water

A

C4H6O3 + H2O —-> 2 CH3COOH

17
Q

functional groups in salicylic acid

A

C-O-H = alcohol

C=O -O-H = carboxylic acid

18
Q

safety considerations of acetic anhydride and sulfuric acid

A

bad burns and MUST be used in fume hood

19
Q

how can excess chemicals be disposed of

A

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

20
Q

how much salicylic acid was weighed

A

3 grams and put in an Erlenmeyer flask

21
Q

what was added to the flask with salylic acid

A
  • 6 ml of acetic anhydride
  • 5 to 10 drops of 18 M H2SO4
22
Q

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

A

heat for 10 mins in water bath

23
Q

what is done with the flask after heating

A

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

24
Q

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

A

filter solid iron through filter paper using buchner funnel

25
Q

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

A
  1. first wash with 5 ml chilled water after let air draw through for 15 mins
26
Q

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

A
  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
27
Q

how is recrystallization completed

A

by cooling solution in ice bath

28
Q

how is the purified crystals collected

A
  1. filtration with the Buchner funnel again
  2. wash with 5 ml cool water
  3. draw air through for 15 mins
29
Q

when does stretching frequency increase

A

as bond strength increases

30
Q

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

A

lowest = single bond (lowest strength)

highest = triple bond (highest strength)

31
Q

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

A

they would vibrate at a LOWER frequency compared to lighter atoms

32
Q

can molecules occupy any vibrational levels

A

NO - only specific ones

33
Q

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

A

NO - must be POLAR

34
Q

what determines the amount of energy a molecule can absorb

A
  1. bond strength
  2. masses of atoms
  3. polar
35
Q

what frequency of light will be absorbed by a molecule

A

only those frequencies that match vibrational energy level differences

36
Q
A
37
Q
A

Chemistry 2000 lab exam (5 decks)

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