What are the kind and number of atoms in the ring portion of t...

Question

What are the kind and number of atoms in the ring portion of the Haworth structure of glucose?

Accepted Answer

Hello everyone. And welcome back. Our next question says, identify and count the atoms present in the ring portion of glo Pinos. Our answer choices are a six carbon atoms and one oxygen atom, B, five carbon atoms and one oxygen atom, C four carbon atoms and two oxygen atoms or D six carbon atoms. So first of all, we see that os ending and we know we're talking about a sugar and we think about the ring form of sugars. They always have to have an oxygen in the ring. And when they form that ring, they form in a hemi acetyl or acetyl form. And so they have one but only one. So one oxygen in the ring, only one. So we know right away that choice is C which says two oxygen atoms and choice D six carbon atoms are incorrect. So C has one, too many oxygen atoms and D doesn't have an oxygen. So we just have the choices A and B six carbon and one oxygen, five carbon and one oxygen. So now let's look further at our name. We see that this is a Pinos and the fact that this says Pinos means we know that this must be a six membered ring. We can have pinos or pinos. A finos is a five membered ring. So here's the thing, we don't even need to remember what type of sugar the base sugar is. You know, in this case, we have this Gulo here, the base sugar would be goos, not a very um well known sugar, but I don't even need to remember anything about goos how many carbons it has, how, where the hydroxy groups are? Because I know I have a six membered ring. And since it's a sugar, one of those members must be oxygen if I've got six atoms in the ring and one of them is oxygen. My answer must be choice B five carbon atoms and one oxygen atom poleo from six membered ring pointing at that. And so choice A is incorrect because six carbon atoms and one oxygen atom would give me a seven member ring, which is not what a pyin nose is now because this is a practice problem. It's not a test on a test. That's the shortcut way to the answer. Um This is a practice problem. So we want to be a little more thorough. So I just want to go through, you know what exactly that would look like. So gulose happens to be a six carbon sugar with an aldehyde at the carbon one position. So draw our aldehyde straight line down and then the horizontal lines for carbons, 234 and five with C h2o H at the bottom carbon six gulose has again, this is de gulose because that's our context in nature. And in gulose, we have carbons at C two C three and C five where the hydroxy group is on the right. So I'm drawing this straight line fissure projection here. So at C two C three and C five, we have oh on the right and then C 40 is on the left. So fill in my hydrogens, my hydroxy groups and then number the carbons to keep them straight. So one through six and now by convention, when we draw these rings, I have a six membered ring, we know that we draw the anomic carbon on the right. In this case, with that aldehyde group, our oxygen is on the top right of that ring. So there's oxygen draw the rest of our six membered ring carbon. One is therefore this carbon on the right go around a number or other carbons. So anomic carbon is going to have a hydroxy group going off of it. Remember this could be alpha or beta. So we'll draw a little squiggle here. Oh With a squiggle. And then our other hydroxy groups, we know that going from fissure projection to the ring structure oh groups on the right point down oh groups on the left point up. So at carbon two, we go down carbon three, our oh group goes down. Carbon four, it goes up and then carbon five has our carbon six coming out of it. C h2o H So now sure enough, when we look at our atoms in the ring, we've got our one oxygen and then five carbons in the ring, there are six carbons in the sugar, but carbon six is here outside the ring. So it doesn't count. So once more, then when we want to identify and count the atoms that are present in the ring portion of glo pyo, we have choice b five carbon atoms and one oxygen atom. See you in the next video.

What are the kind and number of atoms in the ring portion of the Haworth structure of glucose?

Key Concepts

Haworth Structure

Glucose

Atoms in the Ring

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