Understanding Fructose: The Role of Ketone in Reducing Sugar Reactions

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In summary, fructose is a reducing sugar that contains a ketone group which acts as a reducing centre, converting Cu2+ to Cu+ in an oxidation reaction. This process also results in the oxidation of fructose itself. However, the oxidation of a ketone group is typically not possible. The iodoform reaction can be used to confirm the presence of a ketone group in fructose, but it does not involve the use of hydroxide or iodine, which are typically used in reducing sugar tests. Instead, the ketone group is reduced to a carboxylic acid. The isomerization of fructose to glucose and mannose through an enediol and subsequent oxidation in a Benedict's test is a common
  • #1
garytse86
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Fructose is a reducing sugar, and the ketone acts as a reducing centre, which reduces Cu2+ --> Cu+. Therefore fructose itself becomes oxidised.

However, how can a ketone group be oxidised?

I thought: aldehyde becomes oxidised to carboxylic acid
ketone: cannot be oxidised.
 
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  • #2
Try looking up the iodoform reaction.
 
  • #3
How does that help. I know the iodoform reaction confirms any 2-one, 2-ol, 2-al, ethanol or ethanal. i.e. CH3C=O, but no hydroxide / iodine for reducing sugar test?
 
  • #4
Well, from what I remember, the ketone is reduced in this case to a carboxlic acid, although not completely sure. Try finding the mechanism, I just don't have the time right now.
 
  • #5
Yeah, the fructose isomerizes to glucose and mannose via an enediol, which then oxidizes in the standard Benedict's test fashion.

My students happen to be doing that very experiment today.

If you want to oxidize an actual ketone, there's always carbonyl oxides...
 
  • #6
ok, thank you very much :D
 

What is reducing sugar and how does it differ from non-reducing sugar?

Reducing sugar is a type of carbohydrate that can undergo a chemical reaction called reduction. This means that it can donate electrons to another molecule. On the other hand, non-reducing sugar cannot undergo this reaction. The key difference between the two is the presence of a free aldehyde or ketone group in reducing sugars, which allows them to be oxidized and reduce other molecules.

Why is reducing sugar important in food and nutrition?

Reducing sugars play a crucial role in food and nutrition as they are a major source of energy for the human body. They are also used in food as sweeteners and contribute to flavor, color, and texture. Additionally, reducing sugars are involved in important metabolic processes such as glycolysis and the production of ATP, which is the primary source of energy for cellular activities.

How can reducing sugar levels be measured in food?

Reducing sugar levels can be measured using various chemical tests such as the Benedict's test, Fehling's test, or the Lane-Eynon method. These tests involve the reaction of reducing sugars with specific reagents to produce a color change, which can be quantified using a spectrophotometer. Alternatively, reducing sugar levels can also be measured using enzymatic assays or high-performance liquid chromatography (HPLC).

What are some common sources of reducing sugars in our diet?

Reducing sugars can be found in a variety of natural and processed foods. Some common sources include fruits, vegetables, honey, maple syrup, and dairy products. Processed foods such as baked goods, candy, and carbonated drinks also contain high levels of reducing sugars, often in the form of added sugars like sucrose, glucose, and fructose.

How can reducing sugar intake benefit our health?

Reducing sugar intake can have numerous health benefits, including weight loss and reduced risk of chronic diseases such as type 2 diabetes, heart disease, and obesity. High sugar consumption has been linked to inflammation, insulin resistance, and other health issues. By reducing sugar intake, individuals can also improve their overall diet by replacing highly processed foods with more nutritious options.

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