jOeCHEMists, now that we've explored more of the awesome chemistry we can do at the carbonyl position, we have to look no further than the next door neighbor for our next challenge: the alpha carbon. We'll start things off by exploring alpha deprotonation, why it works and how it enables us to generate a new class of nucleophiles that we were initially exposed to with keto-enol tautomerism at the end of OChem I. After learning how to make enolates and enols, we're going to tackle a group of reactions that allow us to make carbon-carbon bonds. There's so much cool chemistry in this series, and it's where I personally discovered that I wanted OChem in my future/life. I hope you feel the same. Leddoit.
https://joechem.io/videos/39 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we'll look at the carbon *next* to the carbonyl carbon: You'd be surprised at how much is going on there. We'll also get acquainted with two new functional groups--enols and enolates.
https://joechem.io/videos/40 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we talk about enolate formation, and how (with an asymmetric carbonyl structure) you can form either a kinetic or thermodynamic enolate depending on your conditions.
https://joechem.io/videos/129 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we revisit the alpha carbon and talk about how we can perform nucleophilic attack and acid base reactions at the alpha position. In the midst of aldol reactions/condensations, Michael Additions, and Robinson Annulations, it's easy to forget this fundamental functionality at the alpha carbon (to perform Sn2, that is). We revisit enolates and also bring back our old friend the enamine, so it may be helpful to review the past video on enamines here on jOeCHEM (linked below). Enamine video: https://joechem.io/videos/35
https://joechem.io/videos/41 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we talk about the Aldol Reaction (in BASIC conditions--yes that matters!). We draw the mechanism and do some examples predicting reaction products. This will be our first new reaction where enolates (the alpha carbon, right?) are used as nucleophiles.
https://joechem.io/videos/130 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we revisit the aldol reaction and do extra example (in both basic and acidic conditions). While we've covered these concepts before, I wanted to make an additional video for some practice and to really drive home the concept of a homo aldol versus a hetero aldol reactino. If some details are hazy, it may be helpful to review the past videos on aldol reactions (in basic + acidic conditions) which are linked below.
https://joechem.io/videos/42 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we take a look at the Aldol Condensation, but this time in acidic conditions (here https://joechem.io/videos/41 we did the same, but in basic conditions). A few things differ now in acid, namely our nucleophile (an enol, not an enolate), and how the reaction must finish (the condensation product).
https://joechem.io/videos/43 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we look at a functional group called enones--or alpha, beta unsaturated ketones--and how they are prime candidates to be attacked by nucleophiles in a 1,4 fashion, as opposed to the 1,2 way we're used to. We will specifically look at the Michael Addition, which is when an enolate nucleophile attacks an enone. However, you can attack enones in a 1,4 fashion with any "soft" nucleophile, and we'll see an example of that by attacking an enone with a cuprate nucleophile.
https://joechem.io/videos/44 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we look at the Robinson Annulation reaction and how to draw its mechanism. It may look scary, but don't worry: I promise it's not. For more Robinson Annulation info, checkout https://joechem.io/videos/45 for predicting Robinson Annulation products quickly and painlessly.
https://joechem.io/videos/45 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we take our knowledge of Robinson Annulations and look at a shortcut method for completing the reaction/predicting the product.
****WARNING, there is a minor mistake I made that I will explain below**** In the first synthesis problem, I forgot to include the ethylene glycol (two carbon diol) that creates two acetals from two ketones. This is in the last step of the synthesis problem (first one while doing retrosynthetic analysis). https://joechem.io/videos/132 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we put many things together that we've learned regarding alpha carbon chemistry and tackle a three synthesis problems. We will also lean on concepts and reactions we've learned earlier in Ochem II and yes, also some Ochem I reactions as well.