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Carbohydrates are one of three classes of primary metabolites and thus natural products. They are polyhydroxylated hydrocarbons and their derivatives. Colloquially, they are known as sugars. This tag may be applied to all questions that concern carbohydrate species in solution, reaction mechanisms ...

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Can Molisch test be used to separate monosaccharides from polysaccharides?

Do the results of Molisch test on monosaccharides have any differences with when it's done to disaccharides or polysaccharides?
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46 views

Are Anomers Epimers?

epimers are the class of stereoisomers which differ along configuration at any carbon in a carbohydrate(generally), And anomers are the kind of stereo isomers that differ at the carbonylic carbon, ...
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29 views

Can sucralose form a syrup?

(Almost) Everyone is familiar with making simple syrup from table sugar and water. I was wondering if pure sucralose is also capable of forming a syrup. I wanted to do an experiment myself, but to ...
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85 views

What is a reasonable mechanism for the following reaction?

Hello all! I'm stuck on this one question and am not sure how to finish the mechanism. What I did was attack the alkyne first with the N farthest to the left. I'm not sure what do to after that though....
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164 views

What are the differences between D and L glucopyranose?

I have just studied the concept of cyclotron in carbohydrates. My reference book used Glucose as an example and began by saying we can find D-glucose or L-glucose: Depending on what enantiomer we ...
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89 views

Can glucose burn in chlorine?

Chlorine is an oxidizing agent, so could it replace oxygen? If so, what would be the products, and how much energy would such reactions release? Do any other carbohydrates burn in chlorine? I cannot ...
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38 views

Why don't aldohexoes (like glucose) form 7 membered rings? [duplicate]

Normally when forming a hemiacetal, the glucose's C5 OH may attack the C1 carbonyl carbon, or the C4 OH may attack to make a glucopyranose (6 membered ring) and a glucofuranose (glucofuranose) ...
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55 views

What are the optimal conditions for the complete acid hydrolysis (using HCl) of potato starch? [closed]

I'm hoping someone can provide the specifics on the optimal conditions required for the complete acid hydrolysis (using $\ce{HCl}$) of potato starch? I will be using an autoclave (~$\pu{15 psi}$ @ $\...
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210 views

Difference in alpha and beta glycosidic bonds [duplicate]

I have learned that the cellulose has a much rigid and orderly branched structure than the starch. However, the only significant difference between them is the different type of bond formed after ...
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1answer
848 views

Why can't amylase digest glycogen?

Amylase is an enzyme that breaks down starch in the form of amylopectin and amylose. Both amylose and amylopectin are formed by alpha glucose joined together by (1-4) and (1-6) glycosidic bonds. ...
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1answer
988 views

Why are polysaccharides not sweet in taste?

Polysaccharides are defined as polyhydroxy aldehyde or ketone which on hydrolysis yield many units of monosaccharides. I got one answer(to my question above) as: On our tongue, we have things ...
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246 views

Identifying the D/L form of any aldose or ketose in cyclic form

I understand that the compound above is a ketose because it has a furanose ring. But, how do we know that it is a "D" form? Is there any general rule by which I can identify if any given aldose/...
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90 views

Carbohydrates: What does “typical nature” mean here?

I am a 12th grader in India. I have understood basic theory on biomolecules. I know about carbohydates (and structures of important saccharides) and $\alpha$-amino acids, proteins, and peptides. This ...
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271 views

Is it possible to make a disaccharide from two fructose monomers? If so, what is its name?

Maltose is a disaccharide made from two molecules of glucose; and sucrose (table sugar) is made from glucose and fructose. Is it possible to combine two fructose molecules to make a disaccharide? If ...
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60 views

Does potassium react with sugars and sugar alcohols?

Metallic potassium can react with simple alcohols, see this answer. It also can react with polyols, e.g. glycerol: Sodium glyceroxide ... can also be prepared from glycerol and an excess of ...
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381 views

How can I extract cellulose in plants using acids?

Me and my classmates are doing a research project about the extraction of nano cellulose from plants to form a biocomposite, which can be a material to form an effective biodegradable material. We've ...
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1answer
32 views

Where does the additional hydrogen in the Fischer depictions of glucopyranose come from?

My book shows this figure of Fischer formula of D-glucose: I don't understand this figure, and I wonder why the upper carbon atoms in both the right and left formulas have 5 bonds. And from where ...
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1answer
3k views

Why are polysaccharides non-reducing sugars?

My book says that polysaccharides are non-reducing sugars, and they form of condensation of >6 molecules of monosaccharides. The condensation involves the carbonyl groups of the sugars, leaving only ...
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1answer
2k views

Monosaccharides configurations (alpha beta, D L) identification

I am really finding it difficult to identify the correct configuration(s) of a given monosaccharide, in fact my friends and I have been trying to solve this, much to our annoyance. In one of our ...
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240 views

What is the correct way to notate conformation preferences of polysaccharides?

In some webpages (1 or 2) are found the way to notate the conformational preferences of monosaccharides such as furanose and pyranose. But, it lacks to give a brief description on how to do it with ...
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1answer
2k views

Why is chitin ordinarily insoluble in water, but soluble after deacetylation? [closed]

Chitin is usually insoluble in water. How does its chemical structure explain this? Furthermore, when chitin undergoes deacetylation, it becomes soluble and forms hydrogen bonds with water. How is ...
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1answer
177 views

How do Invert Sugars deter crystallization in Sucrose solutions?

Invert Sugars, by themselves, are notorious for their reputation to crystallize fast (think honey), but their addition to solutions of Sucrose (think simple syrup) deters the crystallization process. ...
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136 views

Heat and Sugar Syrup Consistency

I make my own sugar syrups and have been observing how heating the syrup to different degrees results in syrups of radically different consistencies, I wonder why. Heating up syrups (4:3 Sugar:Water) ...
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306 views

Why is methyl α-D-glucopyranoside preferentially formed from glucopyranose in acidic methanol?

According to my textbook Organic Chemistry 2e by David Klein, the formation of a glycoside from glucopyranose favors the α form (see picture below). Why does this happen? Shouldn't the equilibrium ...
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203 views

Glycoside Formation Reaction

Whenever we add $\ce{H+}$/ Ethanol to glucose in its hemiacetal form, why doesn't pinacone/pinacolone rearrangement take place in place of nucleophillic substitution. The product would lead to ...
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404 views

What chemicals change color when water and sugar is present?

I am looking to know what chemical can change the color glucose when combined together. In example if I have a bowl of water and glucose. What chemicals, non hazardous can I add to the mixture to ...
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806 views

Why does the fructose monomer in sucrose appear different from isolated fructose?

I understood that the representation of fructose is: But during the formation of sucrose: How did fructose, whose representation is given in the first picture, turn out to be different in the ...
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1answer
390 views

D/L and +/− labels of glucose

I had just started to read about carbohydrates when I came across D-(+)-glucose. My book says that the '+' sign refers to its optical rotation measured through the polarimeter, and that it could ...
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1answer
68 views

Will mixing methyl 2-cyanoacrylate and cellulose make the cellulose harden quickly?

The other day I was gluing together cotton fabric with methyl 2-cyanoacrylate (superglue) and the fabric started heating up and then eventually began smoking. I have been working on making a 2-part ...
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1answer
230 views

D-Threose: reduction and optical activity

I've bumped into this exercise: Judging by the mechanism of reaction between D-threose and $\ce{NaBH4}$, do you think the final product will be optically active? To me looks like a reduction, ...
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1answer
115 views

Can Cellulose Molecules be Synthesized from Glucose?

I am reading that cellulose may be broken down into glucose. This is usually done with some sort of solvent. Is there any way to 'rebuild' these cellulose molecules from glucose?
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105 views

Asking about definitions of word “sugar” in biochemistry

In a lecture about anabolic pathways of sugar, the lecturer was not clear when stating the name of a multiple sugar carrier & it sounded like "dolichol"so is it correct?
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2-Deoxy-D-arabinohexose, 2-Deoxyglucose

Aldrich says that these two names are synonyms of one another. Does anyone know the etymology of arabinohexose used in this context?
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287 views

How to assign peaks to mannose using H-NMR and COSY?

I did a H-NMR experiment with D-mannose in deuterated DMSO. I have difficulty assigning the peaks. I know doublet a is the anomeric centre C1 and that triplet f is the OH attached to C6. Doublets b,c,...
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3answers
4k views

Are glucose and galactose cis-trans isomers of each other?

Glucose and galactose are diastereomers of each other. However, is it correct to say that they are cis-trans isomers of each other? Does it make a difference with regard to terminology if glucose and ...
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3answers
6k views

How do you recognize a carbohydrate molecule?

I am studying carbohydrates in organic chemistry and I am confused a bit on what they are and how you recognize whether a molecule is a carbohydrate or not. For example, will a carbohydrate always ...
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0answers
148 views

Hydrolysis of β-1,2 glycosidic bond

Are there any easy, not enzymatic, ways to hydrolyse $\beta$-1,2 glycosidic bonds like they occur in steviosids? I thought of something like vinegar, which is commonly used to cleave the $\alpha$-1,...
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2answers
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If α-glucose is less stable than β-glucose, why is glucose almost always α in its compounds?

Maltose, saccharose, turanose, trehalose, trehalulose, amylopectin, amylose - they are all α. Why? Also, why is cellulose β?
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161 views

Reducing sugar among the given compounds

The question is to determine which of the following sugars is not reducing? I have the idea that in case of disaccharide sugars in which the monosachharide units are bonded via the carbon containing ...
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1answer
554 views

Structural determination of carbohydrates(sucrose)

I recently came across a question in which we have to find out the number of moles of $\ce{HIO4}$(Periodic acid) which are required for cleavage of $\ce{C-C}$ bonds in sucrose. I went to https://en....
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36 views

What is a polyfuranoside?

I came across this molecule on wikipedia, and all that was written about it was two words: Docosanasaccharide and polyfuranoside. https://en.wikipedia.org/wiki/Chemical_glycosylation#...
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39 views

How to select for 1-4 carbon sugar bond in Chemical Glycosylation?

I am interested in Chemical Glycosylation, specifically the production of cellulose by synthetic means. However, it is difficult to ensure that the glycosidic bond is formed between the 1 and 4 ...
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4k views

In Glucose, how will you prove the presence of the following? [closed]

One carbonyl group 5 hydroxyl groups One primary alcholic group
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1answer
6k views

Does Br2/H2O oxidize all aldehydes?

In many books, it is mentioned that aldehydes are easily oxidized even by mild oxidizing agents. However, I have never seen bromine water explicitly mentioned. But in the carbohydrates chapter, it is ...
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1answer
294 views

Ambigious nature of aldehydic group in glucose

In aqueous solution, α-anomer and β-anomer of glucose remain in equilibrium with each other along with a small amount of glucose in open chain form ($0.02~\%$). The open chain form in ...
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1answer
161 views

Why pyranosides do not mutarotate?

For mutarotation, at least one hemiacetal group must be present in the sugar. Therefore, non-reducing sugars do not show mutarotation. Why? Consider the following reaction: $$\ce{\beta-D{-glucose}...
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157 views

A non-life process making glucose from carbon dioxide and water using electricity or light?

update (Sept. 2018): Here is a bit of news that someone might be inclined to cite in a "No, not yet, but..." answer. If nobody else does after a few days, I'll write an answer myself. NASA has ...
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271 views

Why isn't sucrose a reducing sugar but maltose is? [duplicate]

I read one of the answers for a similar question, According to that it is due to the hemiacetale group converting into a carbonyl group. I don't get why the same thing can't be applied to sucrose ...
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27 views

Quantify Sweetness? [duplicate]

My textbook gives many examples of sweetening agents. For Alitame it says its 2000 times sweeter than cane sugar. Aspartame is 100 times sweeter than sugar. I am wondering how they quantify ...
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1answer
115 views

Why does the AraC arabinose sensing system only respond to the presence of L-arabinose?

I understand that when arabinose is present it interacts with araC and changes it shape, promoting the binding of RNA polymerase with the promoter and GFP is produced. However, I don't understand why ...