2. Aspirin and Penicillin

Question 1

General Synthesis reaction of Aspirin

Answer 1

Aspirin (ACETYL SALICYCLIC ACID)

Synthesis Reaction:
- Esterification (condensation reaction)
- Catalyst can be H2SO4 or H3PO4

Limiting reagent: salicylic acid
Reactant in excess: ethanoic anhydride
(ACIDIC CONDITIONS)
Products: aspirin + ethanoic acid

Question 2

Laboratory synthesis of Pure Aspirin
[NEVER SEEN IN A QUESTION]

Answer 2

1) Reaction mixture is being gently warmed
2) Concentrated catalyst is added.
3) Product is cooled to form crystals
4) Crystals are suction filtered and washed with cold water
- This process removes soluble acids (due
to aspirin’s low solubility in water)
5) Recrystallization is performed to purify aspirin
6) Ethanol and water are added and the mixture is chilled, the crystals are pure.

Question 3

Determining the Purity of Aspirin
(or the identity)

Answer 3

• Melting point between 128 - 140 *C
• IR Spectrum (OH for Acid not Phenol)
• NMR & Mass spec
• X-ray crystallography

Question 4

Solubility of Aspirin

Answer 4

Normal aspirin only slightly soluble in H2O

Is increased by reaction with NaOH (aq) to form an ionic salt.
Can now form stronger ion-dipole interactions with H2O

acetylsalicylic acid + NaOH -> sodium acetylsalicylate

Question 5

Bioavaliability of Aspirin

Answer 5

oral asprin about 50%

INCREASED SOLUBILITY DOES NOT INCREASE ITS BIOAVALIABILITY
- converts back to unionised form in the acidic stomach enviornment

Question 6

Uses of Aspirin

Answer 6

1) Mild Analgesic
2) Anti Coagulant
3) Anti Inflammatory properties (helps w arthritis)

Question 7

Side Effects of Aspirin

Answer 7

1) Bleeding of the lining of the stomach
2) Can cause a synergistic effect when alcohol is ingested simoltaneously (which increases its effectivness)

Question 8

Aspirin as a mild analgesic

Answer 8

• Blocks sensation of pain at the source
• Blocks action of enzymes that produce prostaglandin
• Prevents synthesis of prostaglandin
  (Prostaglandin is responsible for the transmission of pain impulses to the brain and causes fever and swelling.)

Question 9

Storage of Aspirin

Answer 9

NOT IN HOT HUMID PLACES
- because heat increases the rate of hydrolysis and hence a reaction of aspirin with water.

Question 10

Discovery of Penicillin
[NEVER SEEN IN A QUESTION]

Answer 10

Discovered in 1928 by Alexander Flemming (petri dish)
- 1940s saved many lives in WW2

Question 11

Penicillin

Answer 11

Group of antibiotics to treat bacterial infections
- Derive from penicillium fungi
- Can be administered orally or through injection

Question 12

Penicillin mode of action

Answer 12

Beta-lactam ring antibiotics

Question 13

Beta-lactam ring

Answer 13

C - C
| |
C - N

The carbon on the bottom right should have sp2 at 120°, and the other ones should have sp3 at 109.5°
however, the bond angles are all reduced to 90° due to its shape and hence it breaks very easily.

Question 14

Antibacterial Properties of Penicillin

Answer 14

The ring interferes with cell-wall formation

1) When in contact the ring opens and binds irreversibly to the transpeptitdase inhibiting it.

(Transpeptidase is responsible for cross-links in the cell wall)

2) Water can then enter the cell and increase its osmotic pressure to the point of bursting / rupturing.

(trans-people need their penis-illin)

Question 15

Antibiotic Resistance

Answer 15

When more bacteria with resistant traits multiply
Is caused by
- overprescription for minor illnesses
- not following complete prescription

Question 16

Antibiotic Resistance and Penicilin

Answer 16

Resitstant bacteria have penicillinase enzyme making them stronger

EXAMPLE: tuberculosis need a cocktail of antibiotics due to their strong resistance to penicillin

Can be overcomed by Modifying the R side chain of penicillin
- reduces the occurance of resistant bacteria

Question 17

Modifying the R side chain of Penicillin

Answer 17

Increased resistance to stomach acid for oral ingestion
- Penicillin G = Ingested
- Ampicillin = Oral

Overcomes penicillin resistant bacteria

Question 18

Antibiotic Definition

Answer 18

Antibiotics are medicines used to prevent and treat bacterial infections.
Antibiotic resistance occurs when bacteria are able to resist the effects of antimicrobial drugs
When antibiotic resistant bacteria infect humans or animals, the infections they cause are more difficult to treat than those caused by non-resistant bacteria
An example is MRSA (superbug) which is resistant to many commonly used antibiotics.