Identify the sugar in each description. c. A ketose that, when reduced with NaBH 4 , forms D-altritol and D-allitol.

All right. Hello everyone. So this question is asking us to determine the sugar described. This ketose forms the galacto and the tale when reduced with sodium boro option A CD sorbets option B says D psychos option C says D Taos and option D says D fructose. So just to provide a little bit of context for this question, right, recall that sodium bro hydride or an A bh four is a mild reducing agent. And so the aldehyde or ketone functional groups in simple sugars can be reduced into alcohols. If it's an aldehyde, then that's converted into a primary alcohol. But if it's a ketone, then the resulting product is going to be a secondary alcohol. And in the context of sugar specifically, it's worth mentioning that during this reduction, the car bono carbon of the ketone is initially sp two hybridized and in the product is going to be sp three hybridized. And so what that means is that it becomes a chiral center, carbon becomes a chiral center and the carbon oxygen is converted into a hydroxy group. And so the reason why two different products are performed or are produced, excuse me is because the hydroxy group in carbon number two of the product can be either to the right or to the left. Now, one more thing that's worth mentioning here is that as a result of this reaction, this reduction, specifically the suffix OS E in this starting material is converted to the suffix itol in the product. So D galacto is from D galactose and DT tool. Excuse me. Tale is from D Talos. So let's draw the structure of both sugars and then go ahead and draw their products after the reduction. All right. So let's go ahead and start with D galactose. And it's worth mentioning that both of these compounds D galactose and D Talos are although heos, which means that for both of them, carbon number one is going to contain an aldehyde functional group abbreviated here is cho. So in the structure of D galactose, carbon number two has a hydroxy group pointing to the right carbons three and four have their hydroxy groups pointing left and carbon number five has its hydroxy group pointing to the right as well. Cardboard number six is a primary alcohol. So its not Cairo. So now let's compare this with the structure of D Talos. In Taos, we have the hydroxy group of carbon. Number two, pointing to the left and the hydroxy groups of carbons three and four are also pointing to the left. The hydroxy group of carbon number five is pointing to the right and carbon number six is still a cargo. So as mentioned before, right, both of these starting materials, both of these compounds are examples of Aldo heos because they have six carbons in total. And there's an aldehyde functional group. So here after reduction with sodium boro hydride, we get galactical and tali. And in both cases, we're going from the aldehyde functional group on carbon number one to a primary alcohol. So carbon number one becomes a CH 20 But here, the product that we're trying to find that produces both of these reduced products has to be a ketose. It's a keto hexose because our products contain thick carbon. Now, the only difference in configuration between these two reduced products is the orientation of the hydroxy group on carbon number two. This means that the carbonel in the structure of the starting material must have been at that position because as mentioned before, after the carbonyl carbon is made to be a chiral center, the hydroxy group can point right or left. So from there, we have the final product. Carbon number one is a CH 20 carbon number two is the car bottle, carbons, three and four have their hydroxy groups pointing left and carbon number five has its hydroxy group pointing to the right with carbon number six, still a primary alcohol. And so based on this description of the structure, we can identify the sugar as ad tato, which means that our answer is going to be option c in the multiple choice and there you have it. So with that being said, thank you so very much for watching. And I hope we found this helpful.

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28. Carbohydrates

Monosaccharides - Reduction (Alditols)

Organic Chemistry

28. Carbohydrates

Monosaccharides - Reduction (Alditols)

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6:43 minutes

Problem 36c

Textbook Question

Identify the sugar in each description.
c. A ketose that, when reduced with NaBH₄, forms D-altritol and D-allitol.

Verified step by step guidance

Identify the type of sugar described in the problem. The sugar is a ketose, meaning it contains a ketone functional group (C=O) within its structure.

Understand the reduction process. When a ketose is reduced with NaBH4 (sodium borohydride), the ketone group is converted into a secondary alcohol, resulting in the formation of two different alditols (sugar alcohols) due to the creation of a new chiral center.

Analyze the products of the reduction. The problem states that the reduction of the ketose forms d-altritol and d-allitol. These two alditols are stereoisomers, differing in the configuration of their chiral centers.

Determine the ketose that can produce these two alditols. The ketose must have a structure such that reduction at the ketone group leads to the formation of d-altritol and d-allitol. This requires analyzing the stereochemistry of the ketose and its potential reduction products.

Conclude that the ketose in question is d-psicose. When d-psicose is reduced with NaBH4, it forms d-altritol and d-allitol due to the specific arrangement of its chiral centers and the resulting stereochemistry of the reduction products.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ketose

A ketose is a type of sugar (carbohydrate) that contains a ketone group (C=O) in its structure. Unlike aldoses, which have an aldehyde group, ketoses typically have their carbonyl group located at the second carbon atom. This structural difference influences their reactivity and the types of derivatives they can form during chemical reactions.

Reduction Reaction

Reduction reactions involve the gain of electrons or hydrogen by a molecule, often resulting in the conversion of a carbonyl group (C=O) to an alcohol (C-OH). In the context of sugars, reducing agents like sodium borohydride (NaBH4) can convert ketoses into sugar alcohols, which are important in various biological and industrial processes.

Sugar Alcohols

Sugar alcohols, or polyols, are derived from sugars through reduction, where the carbonyl group is converted into a hydroxyl group. Examples include d-altritol and d-allitol, which are formed from specific ketoses. These compounds are often used as sweeteners and have applications in food and pharmaceutical industries due to their lower caloric content compared to regular sugars.

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