jOeCHEMists, let me hit you with a blast from the past: remember Fischer Projections? Well if you did or didn't, they're about to re-enter your world. In this series, we're going to cover carbohydrates. This is certainly an interesting section of Organic Chemistry, because while we will learn some new reactions & mechanisms, we won't spend the majority of our time doign that like we would in a typical section. We'll learn a lot of nomenclature, conventions, methods to draw/represent carbohydates, and a few reactions along the way. It'll be sweet, trust me (heh, get it? Yeah, I'm sure you did. Look, I had to do it, sorry.).
https://joechem.io/videos/79 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll briefly touch on what will be covered in the Carbohydrates series here on jOeCHEM. This series is a bit ~different~ than ones we've encountered in the past, being very nomenclature heavy and less reaction focused.
https://joechem.io/videos/80 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll look at how to represent sugars (monosaccharides) with Fischer Projections. There's some new terminology we need to cover, so we'll talk about how to reference the # of carbons in a sugar, whether a sugar is D or L, and how to properly name a sugar. You may need to memorize 3-6 carbon aldoses and ketoses, so be sure to check with your professor/instructor if you have to or don't have to.
https://joechem.io/videos/81 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll revisit an old friend from the Carbonyls series--hemiacetal formation. So technically this isn't a new reaction, but we're applying it to a new situation, namely sugars. We'll dive into the mechanism and talk about why the ring form of sugars are so heavily favored in the equilibrium that's established between the straight chain and ring forms. This video does use Haworth Projections, so make sure to check out the Haworth Projection video as well https://youtu.be/IpNc0STdzd0
https://joechem.io/videos/82 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll talk about how to represent sugars in their cyclic form via Haworth Projections. We'll cover how to take a Fischer Projection (straight chain form) of a sugar and properly represent it as a pyranose or furanose, ensuring that we honor stereochemistry. We'll also dive into the concept of mutarotation.
https://joechem.io/videos/83 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll explore how you can make esters with a cyclic monosaccharide by throwing in excess acid halide or acid anhydride. You can do a similar thing and create ethers by using excess alcohol and silver oxide.
https://joechem.io/videos/84 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll be exploring what an epimer is, how to identify them, and what conditions support epimerization.
https://joechem.io/videos/85 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll talk about the two ways you can oxidize sugars. In the more mild manner, you can selectively oxidize an aldehyde to a carboxylic acid in an aldose, but if you need to oxidize the "top" and "bottom" of a sugar you can use nitric acid.
https://joechem.io/videos/197 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll talk about how you can reduce sugars using NaBH4 and H2O, and if that sounds familiar that's because it should! We've used this reaction to reduce ketones and aldehydes as early as OChem I and definitely in OChem II when we talked about carbonyls. So kick back and relax, because this is essentially just a small review.
https://joechem.io/videos/198 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll introduce yet another new term to our ever growing vocabulary: glycoside. We'll talk about what a glycoside is, how they form (mechanistically), and cover how to name them.
https://joechem.io/videos/199 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll tackle how to lengthen carbohydrate chains (aldoses specifically), and if that sounds scary I promise it's not. Why, you might ask? Well because you know all the chemistry to do it! We'll use HCN to form a cyanohydrin, and then we'll reduce the nitrile to an aldehyde using DIBAL.
https://joechem.io/videos/200 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll talk about the opposite of lengthening sugar straight chains: shortening them! Here we cover the Wohl Degradation, talking about the reagents involved and highlighting why stereochemistry is less of a concern as opposed to chain lengthening.
https://joechem.io/videos/201 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link) In this video, we'll discuss how to "glue" monosaccharides together, forming disaccharides. We'll cover the two different types of glycosidic linkages, or connections, that can be made between sugars and look at examples of 1,4 alpha & beta glycosidic linkages.
https://joechem.io/videos/202 for video on jOeCHEM and attached worksheet + solution (below video on jOeCHEM aka the link). In this video, we'll look at an example problem where we account for achiral behavior from a sugar after it is lengthened and subsequently oxidized. I've seen this question pop up frequently for students (which serves as a nice little stereochem review), so I wanted to make a video just for it.