synthesis and characterization of ASA Flashcards
what does the synthesis involve
the reaction of salicylic acid and acetic anhydride in presence of catalyst (phosphoric acid H3PO4)
what was salicylic acid derived from
bark of white willow tree
what is the reaction equation for ASA
is aspirin soluble in water
yes, cold water
how can aspirin be isolated
by filtering the chilled reaction solution
why is purification necessary
to remove any unwanted salicylic acid
acetic anhydride
acetic product
acid catalyze
how does acetic anhydride decompose
by the addition of water once formation of aspirin is complete
how can the acetic acid and sulfuric acid be removed from the product
they are water soluble so washing the aspirin with chilled water will remove these ions
what is NOT removed in the wash with chilled water
salicylic acid - not soluble in water
how is FINAL purification done
by recrystallization
how is salicylic acid removed from aspirin crystals
impure aspirin dissolved in warm ethanol before cooled slowly and aspirin crystalizes out of solution leaving salicylic acid and other impurities behind
what on the IR indicates success
disappearance of hydroxyl group and presence of ester
what on the IR indicates failur
presence of hydroxyl group and absence of ester
functional groups in acetylsalicylic acid
C=O-OC - Ester
C=O-OH = carboxylic
ring = aromatic carbon
what product forms when acetic anhydride reacts with water
acetic acid
balanced equation for acetic anhydride with water
C4H6O3 + H2O —-> 2 CH3COOH
functional groups in salicylic acid
C-O-H = alcohol
C=O -O-H = carboxylic acid
safety considerations of acetic anhydride and sulfuric acid
bad burns and MUST be used in fume hood
how can excess chemicals be disposed of
down the sink with lots of water BECAUSE the acetic anhydride will convert to vinegar
how much salicylic acid was weighed
3 grams and put in an Erlenmeyer flask
what was added to the flask with salylic acid
- 6 ml of acetic anhydride
- 5 to 10 drops of 18 M H2SO4
what was done with the Erlenmeyer flask after adding all the regents
heat for 10 mins in water bath
what is done with the flask after heating
add 20 drops of RO water AFTER add 20 ml before cooling in ice bath
after the solution is cooled in ice bath, what is done
filter solid iron through filter paper using buchner funnel
describe the FIRST wash for the solid product with a Buchner funnel
- first wash with 5 ml chilled water after let air draw through for 15 mins
what is done with the impure aspirin after drawing air through and weighed
- transfer to 150 ml beaker and add 10 ml 95% ethanol and warm the beaker till dissolved
- after all crystals dissolved add 20 ml of warm water and cover with watch glass to let cool
how is recrystallization completed
by cooling solution in ice bath
how is the purified crystals collected
- filtration with the Buchner funnel again
- wash with 5 ml cool water
- draw air through for 15 mins
when does stretching frequency increase
as bond strength increases
what has the lowest stretching frequency, what has the highest?
lowest = single bond (lowest strength)
highest = triple bond (highest strength)
what does a larger mass between atoms in a bond mean for stretching frequency
they would vibrate at a LOWER frequency compared to lighter atoms
can molecules occupy any vibrational levels
NO - only specific ones
can a bond be non-polar to be absorbed ( to exhibit changes in dipole)
NO - must be POLAR
what determines the amount of energy a molecule can absorb
- bond strength
- masses of atoms
- polar
what frequency of light will be absorbed by a molecule
only those frequencies that match vibrational energy level differences
