You know who you are, the ones I taught as an undergraduate. The ones I deprived of experiencing the best chemical reaction ever, the Grignard Reaction.
I had a thing for the Grignard Reaction the first time we were introduced during Organic I lecture. It was the first reaction I learned that had its own reagent, aptly named the Grignard Reagent. The name is pronounced Green Yard, but when you are this cool, who cares if anyone can correctly pronounce your name. The Grignard reagent is the pimp daddy of all reagents. It is formed when magnesium wedges its way between the carbon and halogen of an alkyl halide.
Mg: Move over, I am cutting in.
C: Excuse me, we are bonding here.
Br: Hee, hee…
On the other end of this love triangle any carbon structure can be present. This is what made the reaction so intriguing to me. The Grignard Reagent can be made from a primary, secondary, or tertiary alkyl halide (also vinyl and aryl halides). Once it is formed the accumulation of electron density on carbon leaves it ready for action, reaction.
The electron dense carbon on the Grignard Reagent sets its sights on the electron deficient carbon of a carbonyl to form an alcohol. It can react with aldehydes, ketones, expoxides, carboxylic acids, acid chlorides, esters. I thought this had to be the most amazing reagent I had ever seen.
With the versatility of the Grignard Reagent’s alkyl structure and the availability of carbonyl compounds, it was like chemical dress-up; how about this top and these pants or maybe this sweater with this skit, the possibilities seemed endless.
I left Organic I, in the spring, thinking the Grignard Reaction could work miracles. By the time I got to Organic II, three months later, with those nightmare exams that were page after page of synthesis problems, where the starting material was unrecognizable from the product, I had convinced myself that the Gringnard Reaction was the answer for everything:
Want to make an alcohol? Grignard.
Open an aromatic ring? Grignard.
Replicate DNA? Grignard.
Clone a human being? Grignard.
Let’s just say Organic II was not as healthy for my GPA as Organic I. My paper chemistry skills were sub-par, but I was a rock star in the lab, so two years later I got a chance to teach the lab to my underclassmen.
Yet another great thing about the Grignard Reaction, it was fun in the lab too. Until we performed the Grignard Reaction Organic Lab had been taking melting points, properly using the balance, looking up information in the CRC Handbook (you kids with your internet, you don’t know how good you have it!). Maybe there had been a distillation, but this was the first time you evaporated your solvent and suddenly there was a mound of white crystals at the bottom of the round bottom flask. After multiple steps, requiring two lab sessions, there was your product. It was so rewarding.
But my unfortunate class would not get to experience it. Our section met early in the week, before the TA meeting. During the week of the Grignard Reaction we were reminded to tell our students that their labware had to be dry for the reaction to work properly. If the Grignard Reagent encounters water the nucleophilic carbon will pull a proton from water, the remaining OH- will bond to magnesium and the whole reaction will shut down. Entice the carbon all you want with carbonyl groups, it won’t bite. “Hmm,” I thought, “I wonder if my students did that?” This was my first teaching experience, before I realized that not only do you have to tell students everything, you have to tell them in triplicate – in very loud tones – with flailing arms.
It was easy to determine how many students had read ahead and properly prepared for the experiment. One, one student produced crystals. The rest of the class evaporated their ether to find an empty flask. Imagine the disappointment, two days of work, and nothing.
And so I offer my deepest apology for not reminding you of the hazards of the Grignard Reagent and water. Sure there was other synthesis that semester, but none as interesting, versatile, down-right cool as the Grignard Reaction.