Carbonation of Grignard Reagents

Concept: Carbonation of Grignard Reagents

Video Transcript

In this video, I’m going to quickly discuss a really cool way to make carboxylic acids and that's through carbonation of Grignards. It turns out guys that Grignard reagents are really great nucleophiles. They have a very strong negative charge on the R. When they’re exposed to dry ice, what is dry ice? Cold, it’s not real ice. It’s frozen CO2 gas. When you literally pour a Grignard on frozen CO2 gas, what's going to happen? It turns out that CO2 acts like an electrophile just like a carbonyl does. In fact, it's an even stronger electrophile because it has these two extremely strong dipoles. When the Grignard sees the carbon dioxide that’s evaporating because it’s frozen, you’re pouring a liquid on it, the R is going to attack the carbon and push electrons down. What we're going to get is a molecule that now looks like this. I've got my carbonyl, I've got my O negative, and I’ve got my R. Check that out.
In just one step, I went from something that looks nothing like a carboxylic acid to a carboxylate. That's what this is, I get a carboxylate. Now, all I need is a protonation step to take care of the rest. I would use whatever I want to protonate my carboxylate and I just made a carboxylic acid from dry ice. Pretty cool, right? If you put dry ice in your pool, then it makes that dry ice vapor that hangs over the pool. I’m not sure if you guys have seen that. Or you could just pour a Grignard on it and you could make carboxylic acids. I think those are two pretty cool choices. Go science. Alright, so let’s move on to the next video.

Problem: Determine the major product for the following reaction.