PatelJanuExp001


 * What do the Rf values of the original Samples A-E suggest about the sample?**

From the Log of [|Exp 001], 1. Prepared a 50mL stock solution of 0.100g adrenaline, 5mL 1M sulfuric acid and methanol in a flask. 2. 14:47 Placed 1.86mL of adrenaline solution and 2.0mL 1M sulfuric acid in a round bottom flask. A 0.5mL sample of the starting reaction solution was pippetted out (sample A) and placed into a 1 dram vial. Attached the flask to a condenser and into a sand bath and turned the heat on low. 3.. TLC was performed on all samples of the reaction using methanol as the eluent.

sample A Rf= 0.338 sample B Rf= 0.571 The sample began to spread out. sample C Rf= 0.661 The sample continued to spread out. sample D Rf= 0.625 The sample is less spread out than previous samples. sample E Rf= 0.642

- Retention factor, or Rf value, is the ratio of the distance the substance moved to the distance the solvent moved. - Dependent upon the polarity of the compound as well as the solvent, Rf values vary. - Since polar compounds have lower values than non-polar compounds, Sample A can validly proved to be the most polar of all the samples with a value of .338. - The more [|polar] the sample is the slower it moves up the plate and thus causes for a lower Rf value. - Sample E thus is the most non-polar of the samples with a Rf value of .642. - Thus, Sample B-F are becoming increasingly non-polar with increasing Rf values. - In addition, the polarity of the solvent affects the Rf values as well. - Increased polarity causes for the spots to move farther up the plate. - The most effective separation is produced with a solvent that provides [|Rf values] between .2 and .8. - Thus, the use of [|methanol] can be figured out quickly. It produces Rf values of optimal value. - We have seen the demonstration of thin-layer chromatography in Chem 244 Lab (in Experiment 10) as well as understanding polar and non-polar properties in [|Lecture 7] that cause for the separation scheme of Samples A-E to have such Rf values.

[|Graphic of Calculating Rf Values:]



Rf = distance traveled by compound / distance traveled by solvent front