Question

Give TWO pieces of evidence that you've successfully made methyl salicylate. Remember when you cite TLC data, you must refer to their spots by their Rf values.

Answer 1

1) In thin layer chromatography (TLC), compounds are separated based on their attraction to the stationary phase and on the polarity of the solvent used. In the experiment – the synthesize methyl salicylate , salicylic acid, and pure methyl salicylate are spotted on TLC plate, and then place in a solvent (a mixture of hexane and ethyl acetate). All the compounds will have characteristic Rf value in a given mobile and stationary phase.

R_f = Distance traveled by the compound / Distance traveled by the solvent

The purity of substance can be determined from the number of spots and their R_f values. If as synthesized methyl salicylate is pure, it should give only one spot with a corresponding R_f​ value.

2) Other evidence can be obtained by measuring infra-red (IR) spectra of salicylic acid and methylsalicylate. The C-H (2700- 2900 cm^-1) region of the IR spectra differs for these two compounds. Methylsalicylate​ will have well defined bands in this region.