What are sugar alcohols definition types reactions and uses
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Sugar alcohols are organic compounds which are derived from the sweet tasting soluble carbohydrates and contain one -OH group attached to each carbon atom of the molecule. Sugar alcohols are white, water soluble solid compounds. They can occur naturally and can be synthesized by various methods at industrial level.
On consumption, sugar alcohol gives a sweet taste and contributes fewer calories than other sugars. That is why they are extensively used in the food industry. You will be surprised to know that nowadays, most of the candies available in the market do not contain sugars due to health concerns and increasing obesity problem among children. Instead, they are composed of sugar alcohols.
Sugar alcohols come under the class polyols as they contain many hydroxyl groups.
Examples of Sugar Alcohols
Erythritol, Xylitol, mannitol and sorbitol are common examples of sugar alcohols. They are 60-70% as sweet as general sugar but give lesser calories than sugars.
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General Chemical Structure of Sugar Alcohols
They have following general chemical formula – HOCH2(CHOH)nCH2OH
As you can see in the general formula of sugar alcohols that sugars have two fewer hydrogen atoms than sugar alcohols. As sugar alcohols are derived from pentose or hexose sugars so they have 5-6 carbon atoms in the chain and as discussed above they have one hydroxyl group attached to each carbon atom. Sugar alcohols generally are not found in cyclic structures. Although on dehydration sugar alcohols give cyclic ethers.
Synthesis of Sugar Alcohols
Sugar alcohols can be obtained naturally and can be synthesized as well. For example, erythritol is sugar alcohol and can be obtained by the fermentation of glucose and sucrose sugars. While mannitol is produced by hydrogenation of sugars in presence of spongy nickel catalyst. Sorbitol sugar alcohol is also produced as mannitol.
HOCH2CH(OH)CH(OH)CH(OH)CH(OH)CHO + H2 → HOCH2CH(OH)CH(OH)CH(OH)CH(OH)CHHOH
You can see in the above reaction that sugar contains two hydrogen atoms less than sugar alcohols.
Characteristics of Sugar Alcohols
Sugar Alcohols Show Following Characteristics –
They are not as sweet as general sugars and do not contain as many calories as sugars.
Their metabolism is not possible by oral bacteria.
They do not turn brown in color on heating like general sugars.
Dissolution of sugar alcohols is an endothermic reaction.
They give a cooling sensation on consumption.
They do not completely get absorbed into the bloodstream. Their rate of absorption is 50% slower than sugars.
Health Effects of Sugar Alcohols
Sugar alcohols give many advantages over general sugars. They are replacing sugars in the food due to their low calories and sweet taste. Sugars cause tooth decay while sugar alcohols do not contribute to tooth decay as they cannot be metabolized by oral bacteria. Even xylitol sugar alcohol prevents tooth decay.
They are absorbed at a lower rate than sugars in the bloodstream. So, they are perfect for diabetic patients. As they have less impact on blood sugar level. Many sweet food items which are prepared for diabetic patients use sugar alcohols as sweeteners. Although unabsorbed sugar alcohols may cause diarrhoea and vomiting, when consumed in insufficient quantities. It happens due to osmotic effects.
Uses of Sugar Alcohols
Sugar alcohols are widely used in many industries such as food and pharmaceuticals etc. Few of its uses are listed below –
They are widely used as food additives. As they are sweet in taste and generate less calories.
They are used to reduce the aftertaste of many sweeteners.
They do not cause tooth decay and help in prevention of tooth decay.
They are widely used by diabetic patients in their sweet food items.
Their glycaemic index or GI is low, so they help in maintaining the blood sugar level.
Many studies on rats show that xylitol can prevent osteoporosis. As it increases bone volume and mineral content.
Xylitol can increase collagen production so it can help to make you skin healthy.
Various sugar alcohols are being used in baked food items, candies, chewable vitamins, cough syrups, frostings, ice creams, mouthwashes, toothpastes etc.
They are used in the medicines related to eight management.
This ends our coverage on the topic “Sugar alcohols”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Sugar Alcohols in Chemistry Structure Preparation and Properties
1. What is a sugar alcohol in chemistry?
A sugar alcohol is a type of carbohydrate that contains multiple hydroxyl (–OH) groups and is chemically classified as a polyol derived from a sugar. Unlike regular sugars, sugar alcohols have a reduced carbonyl group (aldehyde or ketone) converted into an alcohol group.
- They are formed by the reduction of monosaccharides.
- They contain no carbonyl (C=O) group.
- Common examples include sorbitol (C6H14O6) and xylitol (C5H12O5).
2. How are sugar alcohols formed from sugars?
Sugar alcohols are formed by the reduction of the carbonyl group (C=O) in a monosaccharide to a hydroxyl group (–OH).
- The aldehyde (–CHO) or ketone (C=O) group is reduced.
- This reaction typically uses H2 gas with a metal catalyst such as Ni.
- Example: C6H12O6 + H2 → C6H14O6 (glucose to sorbitol).
3. What is the difference between sugar and sugar alcohol?
The main difference is that sugars contain a carbonyl group (C=O), while sugar alcohols contain only hydroxyl (–OH) groups.
- Sugars (e.g., glucose) are aldehydes or ketones with multiple –OH groups.
- Sugar alcohols (e.g., sorbitol) are fully reduced forms with no C=O group.
- Sugar alcohols are generally less sweet and provide fewer calories.
4. Are sugar alcohols carbohydrates?
Yes, sugar alcohols are classified as carbohydrates because they are derived from sugars and contain carbon, hydrogen, and oxygen in similar ratios.
- They are chemically known as polyols.
- They originate from monosaccharides through reduction.
- They are sometimes grouped as "reduced carbohydrates" in biochemistry.
5. What are common examples of sugar alcohols?
Common examples of sugar alcohols include sorbitol, xylitol, mannitol, erythritol, and maltitol.
- Sorbitol: C6H14O6
- Xylitol: C5H12O5
- Mannitol: C6H14O6
- Erythritol: C4H10O4
6. Why are sugar alcohols called polyols?
Sugar alcohols are called polyols because they contain multiple hydroxyl (–OH) functional groups in their structure.
- "Poly" means many.
- "Ol" refers to alcohol functional groups.
- For example, sorbitol has six –OH groups in C6H14O6.
7. What is the chemical formula of sorbitol?
The chemical formula of sorbitol is C6H14O6.
- It is formed by reduction of glucose (C6H12O6).
- It contains six hydroxyl (–OH) groups.
- It is also known as D-glucitol.
8. How does glucose convert to sorbitol?
Glucose converts to sorbitol by reduction of its aldehyde group (–CHO) to a primary alcohol (–CH2OH).
- The reaction uses H2 with a metal catalyst such as Ni.
- Balanced equation: C6H12O6 + H2 → C6H14O6.
- The carbonyl group is eliminated.
9. What functional groups are present in sugar alcohols?
Sugar alcohols contain multiple hydroxyl (–OH) functional groups and no carbonyl (C=O) group.
- Each carbon typically bears an –OH group.
- They are saturated compounds (single C–C bonds).
- They are classified as polyhydric alcohols.
10. Are sugar alcohols reducing agents?
Sugar alcohols are generally non-reducing compounds because they lack a free carbonyl (C=O) group.
- Reducing sugars contain an aldehyde or ketone group.
- Sugar alcohols have these groups converted into –OH groups.
- Therefore, they do not give positive tests with typical reducing sugar reagents like Benedict's solution.
