Synthesis andAnalysis of AspirinChemistry 1060 Laboratory

Analysis• Purity determination

• Thin Layer Chromatography (TLC)• Separation and identification• stationary phase – silica gel• mobile phase – organic solvent

• Relative attraction to the two phases

• Polarity

Analysis• Thin Layer Chromatography (TLC)

• Retention factor (Rf) values

3 cm

5 cm

Solvent front

Rf = 3/5 = 0.60

Origin

Analysis• Thin Layer Chromatography (TLC)• Salicylic acid (starting material)• Pure aspirin• Isolated product

• UV detection

• Results• Isolated product • Rf of pure aspirin• salicylic acid removed?

UV

Analysis• Structure confirmation

• 1H nuclear magnetic resonance (1H NMR) - or proton magnetic resonance (PMR)

Analysis• 1H NMR

Analysis• 1H NMR

radio-frequency region of the spectrum

Analysis• 1H NMR – Shielding

Analysis• 1H NMR – Chemical Shifts, Chemical Equivalency

CH3 Si

CH3

CH3

CH3

tetramethylsilane(TMS)

Analysis• 1H NMR – Chemical Shifts, Integration

3

1

Analysis• 1H NMR – Chemical Shifts, Complex Patterns

Analysis• 1H NMR – Characterizing starting material and product

salicylic acid

aspirin

OH

O

OH

H

H

H

H

OH

O

O

H

H

H

HO

CH3

Summary

• Goals

Week 1:• To synthesize aspirin, from salicylic acid and acetic anhydride

• To purify the product using recrystallization

Week 2:• To verify the purity and identity of the product using thin layer

chromatography (TLC)

• To further confirm the identity of the product by nuclear magnetic resonance (NMR) spectroscopy