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.

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2D NMR of a Funky Disaccharide

Below you'll find the structure of the disaccharide and three 2D NMR spectra - COSY, HSQC, HMBC. I have to match the signals in the spectra to the nuclei that caused them. Answers to any subset of the ...
Dilara's user avatar
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Stability of alpha vs beta anomer in glucose

As per my knowledge, there seems to be 2 main factors influencing the stability of alpha vs beta anomers of glucose: H - bonding Considering this, beta anomer would be more stable due to the ...
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Can Schiff's reagent respond to hemiacetal?

Glucose responds with both Tollens' reagent $(\ce{AgNO3})$ and Fehling's solution $(\ce{CuSO4}).$ But it doesn't respond when treated with Schiff's reagent (p-rosaniline hydrochloride), the reason ...
znerd's user avatar
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Bioplastic from starch

I am doing research in bioplastic from starch. I have tried many quantities and concentrations of starch, vinegar and glycerol at different temperatures. But I am unable to get a certain result of the ...
Maneeha. Ajmal's user avatar
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How can we prevent retrogradation of starch?

Are there any additives which can prevent retrogradation of starch? I have prepared 13% of starch solution along with 2% of NaCl. The results were bit better. The synthesized gel was flowable with ...
Aqib Mehmood's user avatar
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Why does glucose react with hydroxyl amine and HCN but doesn't give Schiff's test or react with NaHSO3?

I can't understand this because if there isn't a free CHO group then it also shouldn't react with NH2OH and HCN. On the same note can anyone also explain why pentaacetate of glucose not react with ...
Tanush Gupta's user avatar
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58 views

Can Seaweed Be a Thermoplastic?

I was on the Internet, and I saw this post. This post shows a photo of thermoplastic seaweed, which I thought was impossible. ` BTW, if you're wondering what the difference is between a thermoset and ...
Charlie Nicholson's user avatar
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Find the missing chemical structures in the reaction sequence

I came across the following question, where a set of reagents are used, starting from a carbohydrate derivative. I understand that this is some total synthesis reaction, but I cannot find which one. ...
Cyclopropanol's user avatar
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1 answer
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What are the key differences between combustion of starch and sugar

I performed an energy content experiment the other day using a rudimentary bomb calorimeter. The experiment was comparing for the energy release of a sugary food (Arnott's Tiny Teddies) to the energy ...
Thomas's user avatar
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Make ethanol with sourdough [closed]

I have seen a lot of videos on internet and to make ethanol they ferment sugar with yeast but is it possible to ferment sugar using sourdough ?
goAT2160's user avatar
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2 answers
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Are Starch, Amylose and, Amylopectin reducing sugars?

Amylose and Amylopectin; As per the information I've learnt, Amylose is considered a reducing sugar but Amylopectin is not because Amylose has a free "reducing end" which Amylopectin lacks, ...
pointlessHumility01's user avatar
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How does industry separate glucose from fructose using liquid chromatography when producing high-fructose corn syrup?

Can someone explain how the separation of glucose and fructose is achieved using liquid chromatography in the industrial production of high-fructose corn syrup? I've seen references to ion-exchange ...
vossman77's user avatar
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How come in biuret test the copper sulfate doesn't react with the sodium hydroxide?

As I understand the color change in the biuret test is due to the formation of a complex between the peptide (with more than 2 peptide bonds) and the $\ce{Cu^2+}$ ion, from $\ce{CuSO4}$. But before ...
CaptainAmerica Whyso's user avatar
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1 answer
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Why might a prepared 1% solution of glucose take 2 hours to give maximum, stable reading on a glucometer?

I put 1.000g of glucose powder into a 1 L volumetric flask and filled the flask to the 1L line with room temperature distilled water. I then inverted several times for 10 minutes to mix until there ...
Joseph Hirsch's user avatar
1 vote
1 answer
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Converting structures into Fisher projections

I am really struggling with converting pyrano/furanosides into their Fisher projection counterparts. Especially when they are drawn like in the shown projection. When do you know to connect the ...
Abigail's user avatar
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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- ...
smw's user avatar
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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 ...
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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 ...
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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 ...
IAchem's user avatar
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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 ...
Kamal Saleh's user avatar
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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 ...
Krzysztof Dryjka's user avatar
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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!? ...
JustCurious's user avatar
2 votes
1 answer
533 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 ...
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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 ...
Constantthin's user avatar
5 votes
1 answer
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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 ...
Anmoldeep's user avatar
5 votes
1 answer
1k 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-...
CannedOrgi's user avatar
2 votes
1 answer
323 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 ...
Brett Ashcraft's user avatar
-2 votes
1 answer
305 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 ...
Kushagra Agrawal's user avatar
0 votes
1 answer
291 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 ...
Theodore Soriano's user avatar
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1 answer
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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 ($\ce{NH3}$).
Soduthanthanakka's user avatar
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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. ...
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6 votes
1 answer
738 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 ...
J.D. Ray's user avatar
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2 answers
126 views

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

What does per-O-acetylated glucopyranoside mean? Can you please break down the roots?
lostbutterfly's user avatar
0 votes
1 answer
3k 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 ...
qubitybit's user avatar
2 votes
0 answers
865 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-...
squiddy's user avatar
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4 votes
0 answers
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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 ...
JProblems's user avatar
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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 ...
SeanJ's user avatar
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2 votes
0 answers
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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 ...
mojopinos's user avatar
6 votes
2 answers
932 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 }$ $\...
Rahul Verma's user avatar
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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 $11$...
Richard Neumann's user avatar
7 votes
2 answers
3k 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 ...
Sid's user avatar
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2 votes
1 answer
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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 ...
IITM's user avatar
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1 answer
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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 ...
marilu's user avatar
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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 ...
Huzaifah Masood's user avatar
3 votes
1 answer
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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 ...
Phease's user avatar
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-2 votes
1 answer
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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?
Tapi's user avatar
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1 answer
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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 ...
knoftrix's user avatar
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3 votes
1 answer
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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 ...
Tony's user avatar
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5 votes
0 answers
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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 ...
line112's user avatar
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4 votes
1 answer
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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 ...
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