Category Archives: Fall 2010 Organic Chemsitry Lab

The Acid Test for Dehydration

This year we varied the catalytic acid used to dehydrate 2-methylcyclohexanol. The standard procedure for us has used commercial concentrated phosphoric acid 85% (w/w) aqueous solution which has a molarity of about 14.8 M. 2.5 mL acid (0.037 moles) is combined with 11.5 g (0.10 moles) 2-methyl-1-cyclohexanol. This year we also tried sulfuric acid and […]

Full Steam Ahead!

Boiling happens when the vapor pressure of the liquid (interior) equals the surrounding (exterior) pressure. In an open air process the exterior pressure is about one atmosphere. There are two ways to induce boiling: 1) increase the vapor pressure of the liquid by heating, 2) decrease the exterior pressure. In steam distillation the two immiscible […]

How Fast Can This Thing Go?

A Fall semester experiment that we have been doing for a number of years is a kinetic study of the hydrolysis of 2-chloro-2-methylpropane (tert-butyl chloride). This goes well with the quintessential SN2/SN1 chapter covered Fall semester. It is also one of the very few kinetic experiments I have seen that is appropriate for Organic Chemistry. […]

A Matter of Scale

This year we tried to quantitate the recovery of caffeine isolated from beverages (an other caffeine sources) with HPLC. Normally, I suggest the mass difference method. Obtain the mass of the empty beaker, add the dried dichloromethane extract, evaporate the dichloromethane in a hot water bath, and reweigh the beaker with the caffeine residue. We […]

The Art and Science of Recrystallization

Recrystallization as a means of purifying organic compounds is a time honored method. Long before Ultra High Performance Liquid Chromatography and Supercritical Fluid Chromatography there was recrystallization. Of course, recrystallization is directly related to solubilities. The science of recrystallization is that a compound may be appreciably more soluble in a hot solvent than a cold […]

The Liquid-Liquid Shell Game

In the classic shell game, an object is placed under one of three shells and the shells are skillfully manipulated until it is not clear to anyone but the instigator under which shell the object resides. In the liquid-liquid shell game a mixture of two compounds is dissolved in ether and extracted with three different […]

TLC = That’s Lousy Chromatography?

This year I changed one of the solvents in the TLC lab that begins the first semester of Organic Chemistry lab. Instead of dichloromethane, we used ethyl acetate. Ethyl acetate is a less hazardous and more environmentally friendly solvent that dichloromethane. I thought the solvent strength on silica gel would be similar between the two. […]

Could You Repeat the Question Please?

It seems that even the most carefully written question will be misunderstood by a few students. The author of the question usually has a particular result in mind and composes the question in this frame of reference. Students approach the same question from any number of different frames of reference. I imagine some approaches are […]

Ah-Ha

During the molecular modeling activity I have described before (Model Students, Molecular Mechanics), there is a little moment of discovery. The students make and draw four constitutional isomers with molecular formula C2H5NO2 to answer questions 1 through 9. All the constitutional isomers they have made so far have a double bond. On question 10 they […]