Questions tagged [carbohydrates]

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 and structures.

Filter by
Sorted by
Tagged with
4 votes
0 answers
20 views

Are substituted sugar/carbohydrate derivatives such as sucralose still sugars/carbohydrates?

Sucralose is made from sucralose, with chlorination of 3 of the hydroxyl groups. If broken up into the 2 saccharide-type units, you'll get 1,6-dichloro-1,6-dideoxyfructose and 4-chloro-4-deoxy-D- ...
user avatar
  • 49
2 votes
0 answers
41 views

Origin of oxygen content among the products of burned carbohydrates

For simplicity, I am only considering complete combustion. I am ignoring variants such as deoxyribose, just pure carbohydrates. Balancing the equation is easy due to the definition of carbohydrate: we ...
user avatar
  • 772
0 votes
0 answers
56 views

Carbohydrates with two hydroxyl group on one carbon atom?

Every carbohydrate I keep encountering so far has only one hydroxyl (–OH) group attached to every carbon atom in the carbon chain (in Fischer projections): either on the left, or on the right of the ...
user avatar
  • 101
0 votes
0 answers
22 views

How to tell if Neu5Ac is in D/L form and alpha/beta form?

As shown in the figure below, I want to make sure if the last Neu5Ac sugar on the left-hand side is in the D-form or L-form. My understanding is that if the sixth carbon is pointing upward, then the ...
user avatar
4 votes
0 answers
25 views

Planning regio selective protection of functional groups in glycochemisty

Lately I was trying to get a thorough understanding of some questions, I have delved into many research resources such as Scifinder, Google Scholar, and Organic Chemistry Portal. but I'm not satisfied ...
user avatar
  • 41
0 votes
1 answer
383 views

When oxygen is connected only to carbon, are then the oxygen and carbon connected with a double bond?

My teacher showed us three molecules: a carbohydrate molecule, a protein molecule, and a lauric acid molecule. I noticed that, when an oxygen atom is connected to one carbon atom and isn't connected ...
user avatar
0 votes
1 answer
76 views

Does changes in pH affects cyclic form of glucose in water solution?

Glucose in water solution is mainly in cyclic form. Both base and acid can catalize formation of hemiacetal, but in distinct mechanisms. I found information that monosacharides eg. glucose exist ...
user avatar
0 votes
1 answer
215 views

Haworth projection of Sucrose

I was searching for the Haworth projection of sucrose and I got this image from wikipedia (and much of the internet). (wikipedia link: https://en.m.wikipedia.org/wiki/Sucrose). But isn't it wrong!? ...
user avatar
1 vote
1 answer
152 views

Reducing sugars and redox potential

I am wondering if reducing sugars are those that can act as reducing agents, and they act as such with Tollens and Fehling reaction, then what's the redox potential here? And is it a reversible ...
user avatar
  • 75
0 votes
1 answer
447 views

Dextrose equivalent values (DE) of the most common sugars

What are the dextrose equivalent values (DE) of lactose, and other common sugars? Some data like the values for sucrose (0), maltodextrin (x<20), maltose (52), and glucose (100) can be found at ...
user avatar
5 votes
1 answer
268 views

Ring Flip of glucose

I have recently read about mutarotation of glucose specifically I am familiar with how cyclic structures like substituted cyclo-hexanes exist in an equilibrium of both their chair conformers. The ...
user avatar
5 votes
1 answer
295 views

Why does α-ᴅ-glucose form at a lower temperature than β-ᴅ-glucose?

β-ᴅ-glucose is more stable than its α-anomer due to the fact that all the −OH groups occupy the equatorial position. If this is the case, then why does α-ᴅ-glucose predominate at 30 °C while β-ᴅ-...
user avatar
2 votes
1 answer
104 views

Looking for a compound that when mixed with sugar will burn when a drop of water is added

Years ago, I watched a Johnny Carson episode where a guest on the show mixed a compound with ordinary table sugar and added a drop of water and the mixture burst into flames. I went and bought the ...
user avatar
-2 votes
1 answer
97 views

D and L configuration of monosaccharides

I got this question in the last week's test from Organic Chemistry. I am a bit confused in assigning D and L configuration. Help me understand the topic of D and L configuration and help with this ...
user avatar
0 votes
1 answer
110 views

Phase of reaction between glucose and potassium cyanide to form amygdalin

I'm trying to write a detective-fiction novel, and I was wondering if potassium cyanide reacts with sugar only if the glucose for the amygdalin to form is dissolved in liquid or does it react even if ...
user avatar
9 votes
1 answer
836 views

Can sugars dissolve in liquid ammonia?

Can monosaccharides and disaccharides dissolve in liquid ammonia due to hydrogen bond formation? My rationale is that these sugars may be able to form hydrogen bond with ammonia ($\ce{NH3}$).
user avatar
0 votes
0 answers
315 views

Haworth structures of sucrose and lactose

The haworth structures of lactose and sucrose is My question is regarding the glyosidic linkage, in lactose it is represented as a zig zag and in sucrose it is a "V". What does that mean. ...
user avatar
6 votes
1 answer
371 views

What is the carbon content, by weight, of vegetable oil?

I have only a high school understanding of chemistry, so please bear with me and my ham-fisted question. I’m trying to understand the carbon content in vegetable oil. I get that various oils have ...
user avatar
  • 169
-1 votes
2 answers
62 views

What does per-O-acetylated glucopyranoside mean? [closed]

What does per-O-acetylated glucopyranoside mean? Can you please break down the roots?
user avatar
0 votes
1 answer
811 views

Pyranose v/s Furanose form of Glucose and Fructose

According to my textbook (Class 12 NCERT Chemistry): Fructose also exists in two cyclic forms which are obtained by the addition of —OH at C5 to the C = O group. The ring, thus formed is a five ...
user avatar
2 votes
0 answers
246 views

Can I extract solid sugar from any fruit juice at home?

The goal here is to isolate the sugar from all other compounds in the juice. In this case, I'm using apple juice and grape juice. The sugar does not need to be edible, as it is being used to make r-...
user avatar
  • 21
4 votes
0 answers
46 views

Carbohydrate Chemistry for Candy Making

I am trying to understand the different behaviors of sugar syrups when it comes to candy making. Specifically, maple syrup vs molasses. In making maple candy, pure maple syrup is heated to soft ball ...
user avatar
  • 149
1 vote
0 answers
46 views

Glucose and related aldohexoses are interconvertible with a little base. Does anybody know how much of each sugar is present at equilibrium?

If you add NaOH to D-glucose in water, a mixture of almost all aldohexoses will arise over time, including mannose and fructose. I wonder how much of each will be present and what could explain the ...
user avatar
  • 111
2 votes
0 answers
198 views

Do enzymes that digest ᴅ-glucose react with ʟ-glucose?

ᴅ-Glucose is common in nature and ʟ-glucose is synthesized in the lab. I know that humans can't use ʟ-glucose in their aerobic pathways because it doesn't match the active site of the enzyme, but why ...
user avatar
5 votes
2 answers
532 views

Reaction of glucose acetal with acetic anhydride

The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1), Consider the following reactions: $\ce{ (i) Glucose + ROH ->[dry HCl] Acetal ->[$x$ eq. of (CH3CO)2O] acetyl derivative }$ $\...
user avatar
  • 2,797
-2 votes
1 answer
141 views

Sucrose skeletal formula - missing Carbon and Hydrogen [duplicate]

I was reading the Wikipedia article about Sucrose, when I noticed that the skeletal formula was missing some $\ce{C}$ and $\ce{H}$ atoms. The chemical formula being $\ce{C12H22O11}$, I counted the $11$...
user avatar
4 votes
2 answers
1k views

Oxidation of hydroxyl groups of glucose

In all oxidation reactions of glucose, it seems that the aldehyde group alone gets oxidised and none of the hydroxyl groups. In one reaction with nitric acid, the aldehyde group and the terminal ...
user avatar
  • 65
2 votes
1 answer
646 views

Do all reducing sugars show mutarotation?

Do all reducing sugars show mutarotation? I studied that for a sugar to be reducing it must possess a free aldehydo or keto group. Also, for a mutarotation interconversion between α- and β-forms of ...
user avatar
  • 151
0 votes
1 answer
371 views

what is a sugar unit?

How a sugar unit is defined? I am trying to understand the structure of calicheamicins, and it is noted that They consist of an enediyne headpiece and a modified carbohydrate tail consisting of four ...
user avatar
  • 27
1 vote
0 answers
409 views

Where does the beta notation come from in the alpha 1,2 beta glycosidic bond (in sucrose)? [duplicate]

I am confused as to where the beta is coming from (in the alpha-1,2-beta glycosidic bond in sucrose). I understand that the alpha is from the anomeric carbon of the glucose, but I don't see how the ...
user avatar
1 vote
0 answers
273 views

What is the chemical equation for a Maillard reaction? [closed]

I'm a 10th-grader in my first year of chemistry. We have an assignment to make a brochure about a certain reaction, and I'm studying Maillard reactions. Does anyone know the chemical equation ...
user avatar
  • 21
3 votes
1 answer
969 views

Why are there two structures of L-Glucose in the Fischer projection?

We are told that L-Glucose is an enantiomer of D-Glucose, which would mean that they are mirror images of each other. But then we're also told that the L and D forms is determined by the spacial ...
user avatar
  • 83
-2 votes
1 answer
224 views

How is levulinic acid formed from sucrose? [closed]

I came across the following question: Sucrose on treatment with conc. $\ce {HCl}$ produces? The answer is given as levulinic acid. So how exactly does sucrose produce levulinic acid?
user avatar
  • 315
2 votes
1 answer
289 views

Why glucose and other similar carbohydrates are oxidised fully by HIO4?

$\ce{HIO4_{(aq)}}$ requires the vicinal diols to have syn configuration, as it forms a cyclic periodate ester. But glucose does not have syn configuration at C3, and if you consider cyclic forms of ...
user avatar
  • 355
2 votes
1 answer
1k views

Reactions which confirms the presence of cyclic structure of glucose [duplicate]

Are there any reactions that can be explained only on the basis of the cyclic structure of glucose rather than the open chain thus confirming its presence in the solution? Like a reaction that can ...
user avatar
  • 252
5 votes
0 answers
95 views

Can a per-acetylated sugar anomerize?

So I have a question concerning a reaction mechanism for the reaction below. I know for certain that I get the alfa anomer, but I can't explain it. When I draw out the mechanism it doesn't make sense ...
user avatar
  • 91
3 votes
1 answer
5k views

Oxidation of fructose with conc. HNO3

I recently studied carbohydrates. I was taught that fructose on oxidation with strong oxidizing agents like concentrated $\ce{HNO3}$ yields glycolic acid and tartaric acid along with trihydroxy ...
user avatar
  • 1,085
-1 votes
1 answer
792 views

Fischer's proof of the structure of glucose

To differentiate between Mannose and Glucose , Fischer developed a series of reactions to make the aldehyde group to alcohol and terminal alcohol to aldehyde. What was this series of reactions ? Even ...
user avatar
0 votes
1 answer
206 views

Haworth's research of glucose

Firstly haworth used CH3I/Ag2O with glucose which replaced 5 H by CH3 forming a acetal which locked the anomer and stopped the equilibirium of ring chain tautomerism. Under dilute acidic conditions ...
user avatar
1 vote
0 answers
107 views

Question on identification of a compound

Question: Multiple correct answers are possible My Approach: I just found structure Q for all options A, B, C and D for which I have uploaded the structures below with their corresponding options. ...
user avatar
  • 1,982
-1 votes
1 answer
329 views

What is the difference between the sugar in a fresh fruit and the sugar in a juice?

In this paper of the WHO, there is a distinction between intrinsic sugars, who are incorporated within the structure of intact fruit and vegetables, and sugars naturally present in fruit juices. (page ...
user avatar
  • 101
1 vote
2 answers
758 views

What reagents can be used to distinguish pentose and hexose sugars?

I have been asked how I can differentiate D-glucose and D-xylose using the following reagents / reactions: Orcinol Benedict's test Ammoniacal silver nitrate $\ce{FeCl3}$ $\ce{C6H5SO2Cl}$,...
user avatar
7 votes
1 answer
1k views

Does cooling a potato change the nature of its carbohydrates?

A talk-show guest of Joe Rogan claimed that cooling a potato after cooking creates "resistant starch" that's better for human consumption https://www.youtube.com/watch?v=niwqfwA2Lb8 The claim is ...
user avatar
  • 387
10 votes
1 answer
3k views

How long would it take for sucrose to undergo hydrolysis in boiling water?

I was reading the book Cocktail Codex and there was a snippet on avoiding boiling sugar and water to make simple syrup that made me a bit skeptical. Here it is: Heat also affects the molecular ...
user avatar
  • 219
2 votes
2 answers
294 views

Will (3R,4S,5R)-1,3,4,5,6-pentahydroxyhexan-2-one tautomerise in nitric acid?

The following question was sent to me .The question is " Which of the following is A ?" The given answer was a,b,c Background If both ends of an aldose chain are oxidized to carboxylic ...
user avatar
3 votes
1 answer
2k views

How are glycosidic linkages formed?

Consider glycosidic linkages in disaccharides. I know a condensation reaction occurs, with the loss of water. But which OH is lost? The O in the linkage belongs to which monosaccharide? Example: ...
user avatar
2 votes
0 answers
324 views

Fehling's solution - What is the shelf life of the unmixed A & B components?

If you prepare two separate solutions of Fehling's A and Fehling's B, what is the shelf life likely to be? Will the effectiveness of the solution diminish over time? The literature recommends ...
user avatar
1 vote
1 answer
425 views

Why doesn't open-chain glucose react with water readily in aqueous solution?

Though the exact number given varies from 0.02% to 3%, it's well agreed that glucose spends a very small percentage of its time in aqueous solution as a linear aldehyde. Glucose's overwhelming ...
user avatar
6 votes
0 answers
99 views

Why the use of MD simulations is less popular for the study of carbohydrates?

In classical all-atom MD simulations, the force fields for proteins, nucleic acids and lipids seem to be more well developed than carbohydrates. It seems to me that the use of MD simulations is not so ...
user avatar
4 votes
2 answers
2k views

How does existence of alpha and beta form of glucose prove that it exists as a cyclic structure

My book says that Glucose is found to exist in two different crystalline forms which are named as $\alpha$ and $\beta$. Next it says that This behaviour could not be explained by the open ...
user avatar
  • 285