D vs L Enantiomers - Video Tutorials & Practice Problems

D vs L Enantiomers Concept 1

When it comes to mono sac rides, we say they can exist as either ad in anim or an L in anim D versus L stereo. Chemistry is determined by the pul carbon. When we say penultimate here, we're talking about the last chiral carbon. Here we have D Bulos versus is L riots. So how are we able to determine which one is, which we're gonna say for the D in anum? The pul oh So again, we're talking about the last Carol carbon which is this one that's circled. If the oh is on the right side, then it's D it's ad sugar Elling answer here. The pult oh Again, we're talking about the last house center, the one on the very bottom. If it's on the left side, left L then it's an L sugar. OK. So left L sugar, L sugar. So again, we're looking at the last Carol Center looking to see what side do, which is on, is it on the right side making it ad sugar? Is it on the left side making it an L sugar? And we're gonna say what's important here is that when we're talking about carbohydrates, at least from a chemistry aspect, we're gonna say most carbohydrates found in nature are going to be D sugars. So D sugar is the predominant sugar form they're gonna look at right. So just keep this in mind when we're talking about D versus L sterile chemistry, it's really looking at the last Carol Center in determining what side is the, oh, on, is it on the left side or is it on the right side?

D vs L Enantiomers Example 1

In this example question, it says identify each monosaccharide as D or L in an tumor. So remember to determine D or L stereo chemistry, we look at the pent ultimate carbon or the last chiral carbon, the last chiral carbon would be this one and this one if the oh group is on the right side, that makes it ad sugar. So this would be ad in answer. And then if the oh is on the left side, left L, then it's an L in an tumor. So we would say here that for structure A represents ad anti since the O which is on the right side, on the last chiral center. And then we'd say B is an er since the oh is on the left side of the last chiral center, right. So that's how we approach this particular example question.

D vs L Enantiomers Example 2

In this example, question, it says to draw ac four epimer of D fructose. All right. So what we're gonna do first is number this monosaccharide and just like with typical naming, we're gonna number it from the end closest to our carbon carbon. So we start up here. 12345 and six. Here it says it wants ac four epimer. Remember an epimer is a type of dire stamer where two structures are the same in all their chiral centers except for one place here. They're telling us where that one difference is. It happens at carbon number four C four. So what I'm gonna do here is I'm gonna draw the C four epimer of the fructose. We're gonna say the CH two H say the same, the carbon carbon stays the same. And so we're gonna have here 12345 and six C three stays the same. The difference is a carbon number four. So we're gonna flip it the oh, now here is on the left side instead of the right and the H is over here, C five stays the same. So this structure here represents the C four epimer of the fructose. We've only changed the chiral configuration or chiral center at carbon. Number four. This is what makes it ac four epimer.

Label each as D-enantiomer, L-enantiomer, epimer or neither of Talose.

• A. D-enantiomer, epimer, L-enantiomer 
• B. epimer, neither, L-enantiomer
• C. epimer, L-enantiomer, D-enantiomer
• D. neither, epimer, D-enantiomer

Identify the given molecule as diastereomer or epimer of D-sorbose.

• A. Diastereomer 
• B. Epimer