a. Suppose you have a sample that is made up of carbon and hydrogen only and you want to do a TLC analysis on it. What will be a suitable solvent to develop the plate?
One suitable solvent might be hexane or a solvent mixture of hexane (nonpolar solvent) and acetone? Since it is a hydrocarbon, it is nonpolar, so it would travel more quickly in a polar solvent. If its R_f increases in a polar solvent, it might run too close to the TLC plate’s end?
b. What if you have a 50/50 mixture of carboxylic acid and a saturated hydrocarbon?
Carboxylic acid is very polar and moves the slowest. A saturated hydrocarbon is nonpolar and travels the most on the slide. Would a solvent of moderate polarity, such as acetone, work, or must a mixture of solvents be used? (How does one know when to use a mixture of solvents?)