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Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

Table of contents
24. Carbohydrates

Monosaccharides - Haworth Projections

Haworth projections are simplified drawings of sugars in their cyclic form, imagining that the ringed structure is planar


Monosaccharides - Haworth Projections

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Now we're gonna talk about another type of representation that's very important for sugar chemistry. And that's the hall worth projection. So, guys, how worth projections are simplified drawings of sugars in a cyclic form, imagining that your ring is planner. Now we know that it's not planner. We know that it's in a puckered chair confirmation according to the rules of cyclo hexane that we learned in or go one. But we use these simplified structures or a lot because they're just easier to draw. Okay, now what do you need to know about converting a mono sacha ride chain into ah, haul Worth, guys, It's exactly like a cyclo hexane, just easier. The an America carbon note is always at the far right in a hall worth projection, which is exactly the same a cyclo hexane. You're an American position. You're one position should always be there. So that means this carbon is the same as that carbon there. Okay. And in the same way, you're gonna number going clockwise. So it's gonna be 2345 And remember, this is actually six. Okay, so let's say it Also, it says this is true for both pira nose and for nose rings. So in this case, thes air pira nose rings. But if there were for a nose fiber rings, you're an American. Carbon should still go to the right. Now, this practice problem is pretty straightforward. It's a properly number the following haul Worth projections identify each animal and predicted an American equilibrium. Well, guys, I already started on this problem before we even began because I started showing you guys how your rights carbon should be number one, right? It should be your an americ. So that means that this is your one and that you should just go clockwise like you would with a regular cycle. Heck sane. Meaning that this is also for five six. Okay, Now, can you guys explain to me why carbon six is going up? Why is carbon six going off? Because once again, we have a d. And I'm sorry we have a d glucose, which is like a D stereo. I summer and D always goes up with the stereo determined stereo descriptor always goes up. Okay. Now, how can we identify each animal? So notice that this ohh is faced down, and this ohh has faced up. So how do we figure out which ones Alfa and which was Beta? We'll notice that for both of these, the stereo descriptors faced up. Meaning that this is a trans. And this is a sis. So, guys, the same rules we're gonna apply This is the Alfa An Imer. And this is the beating animal. Okay, now, guys, I told you, you're not going to be responsible to know when Alfa is more prevalent over beta. At least not now. That that you need more knowledge for that. But I did already show you guys what the in America equilibrium was specifically for d glucose. And remember which one was favorite. Remember, it was actually the beta, right? It was actually the beta. So I'm gonna go ahead and draw that. The an American equilibrium is more towards the beta and less towards the Alfa. Simply because I already showed you this same exact molecule. Okay, Just because it is this way for manos it might be different, but for glucose, we know that one specifically, we know that it's going to go to the right. Okay, Awesome guys, that wasn't so bad right now you have another even easier way to represent, uh, mono sack rides. Let's move on to a practice problem.

Draw the Haworth Projection that would be expected from cyclization of D-Fructose into α-D-Fructofuranose

Don't forget to fill in the OH I forgot to draw on carbon #4 in the above problem! Great job, guys!