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Closed Chain Structure Of Glucose

Cyclic Structures Of Monosaccharides

Cyclic Structures Of Monosaccharides

16.4 Cyclic Structures of Monosaccharides Define what is meant by anomers and describe how they are formed. So far we have represented monosaccharides as linear molecules, but many of them also adopt cyclic structures. This conversion occurs because of the ability of aldehydes and ketones to react with alcohols: In some cases, OH and carbonyl groups on the same molecule are able to react with one another in an intramolecular reaction. Thus, monosaccharides larger than tetroses exist mainly as cyclic compounds ( Figure 16.5 "Cyclization of D-Glucose" ). You might wonder why the aldehyde reacts with the OH group on the fifth carbon atom rather than the OH group on the second carbon atom next to it. Recall from Chapter 12 "Organic Chemistry: Alkanes and Halogenated Hydrocarbons" , Section 12.9 "Cycloalkanes" , that cyclic alkanes containing five or six carbon atoms in the ring are the most stable. The same is true for monosaccharides that form cyclic structures: rings consisting of five or six carbon atoms are the most stable. D-Glucose can be represented with a Fischer projection (a) or three dimensionally (b). By reacting the OH group on the fifth carbon atom with the aldehyde group, the cyclic monosaccharide (c) is produced. When a straight-chain monosaccharide, such as any of the structures shown in Figure 16.4 "Structures of Three Important Hexoses" , forms a cyclic structure, the carbonyl oxygen atom may be pushed either up or down, giving rise to two stereoisomers, as shown in Figure 16.6 "Monosaccharides" . The structure shown on the left side of Figure 16.6 "Monosaccharides" , with the OH group on the first carbon atom projected downward, represent what is called the alpha () form. The structures on the right side, with the OH group on the first carbon atom point Continue reading >>

Dc-1: Lesson 21a. Structure Of Glucose - Open Chain And Ring Structure And Evidences For The Ring Structure

Dc-1: Lesson 21a. Structure Of Glucose - Open Chain And Ring Structure And Evidences For The Ring Structure

Lesson 21A. STRUCTURE OF GLUCOSE - OPEN CHAIN AND RING STRUCTURE AND EVIDENCES FOR THE RING STRUCTURE STRUCTURE OF GLUCOSE - OPEN CHAIN AND RING STRUCTURE AND EVIDENCES FOR THE RING STRUCTURE The structure of carbohydrates (taking glucose as an example) is given below 21.A.1.1 Open chain structure (Bacyers formula) Arrangement of six carbon atoms- a straight chain One of the five OH groups as CH2OH and in terminal position Fig. 21.1 Open chain structure of glucose In glucose- for asymmetric carbon atoms- therefore 24 =16 stereoisomeric structures possible Therefore essential to define the configuration about each of the four asymmetric carbon atoms Glucose- assigned the configuration as shown here Horizontal lines represent bonds coming out of the plane- i.e. towards us. Vertical lines represent bonds going behind the plane i.e. away from us. Chemistry of glucose- anomalies in behavior Lacks some characteristic reactions of aldehyde Kiliani cyanohydrins synthesis is not rapid (difficult) Exists in two isomeric forms and both undergo mutarotation These anomalies- explained on the basis of cyclic (ring) structure resulting from intramolecular hemiacetal formation A hemiacetal a compound formed by reaction between aldehyde and alcohol Continue reading >>

Pyranoses And Furanoses: Ring-chain Tautomerism In Sugars

Pyranoses And Furanoses: Ring-chain Tautomerism In Sugars

Pyranoses and Furanoses: Ring-Chain Tautomerism In Sugars A simple question!but one withmany right answers. The first question to ask, which we covered in our recent post on D- and L-sugars , is: Which enantiomer are you talking about?. If, by glucose, you mean the enantiomer we commonly encounter as table sugar, then youre referring to D-glucose. In its open chain form, when drawn as a Fischer projection, D-glucose looks like this: The fact that I had to specifyopen-chain form might tip you off that something is amiss. Thats because glucose, like a snake that bites its own tail, or a belt can adopt a cyclic form as well. And not just one cyclic form, but several! Before divinginto these, its worth a quick refresher on the two main functional groups in glucose (and other sugars) which make this possible: hydroxyl groups and aldehydes (or ketones, in the case of keto-sugars like fructose ). Hydrates, Hemiacetals, and Cyclic Hemiacetals You may recallthat aldehydes (and ketones, but well focus on aldehydes here) can reversibly react with water to form hydrates. Hydrates form readily in solution, but they tend not to be easy to isolate; the equilibrium tends to favor the starting aldehyde. [ Note 1 ]. [Refresher on mechanism click here to bring up a picture of the mechanism at work ] Similarly, aldehydes can react with alcohols to form hemiacetals. Like hydrate formation, hemiacetal formation is an equilibrium and theequilibrium tends to favor the starting aldehyde. [If you heat with acid, excess alcohol and sequester the water that forms, it forms an acetal ; this isnotin equilibrium with the hemiacetal,which is why acetals are a great protecting group for aldehydes/ketones]. Mechanism, if you need a refresher [ link to image ] Heres the twist and the relevance to glucos Continue reading >>

Carbohydrates

Carbohydrates

Carbohydrates are the most abundant class of organic compounds found in living organisms. They originate as products of photosynthesis, an endothermic reductive condensation of carbon dioxide requiring light energy and the pigment chlorophyll. As noted here, the formulas of many carbohydrates can be written as carbon hydrates, Cn(H2O)n, hence their name. The carbohydrates are a major source of metabolic energy, both for plants and for animals that depend on plants for food. Aside from the sugars and starches that meet this vital nutritional role, carbohydrates also serve as a structural material (cellulose), a component of the energy transport compound ATP , recognition sites on cell surfaces, and one of three essential components of DNA and RNA. Carbohydrates are called saccharides or, if they are relatively small, sugars. Several classifications of carbohydrates have proven useful, and are outlined in the following table. sugars having an aldehyde function or an acetal equivalent. sugars having a ketone function or an acetal equivalent. sugars oxidized by Tollens' reagent (or Benedict's or Fehling's reagents). sugars not oxidized by Tollens' or other reagents. Carbohydrates have been given non-systematic names, although the suffix ose is generally used. The most common carbohydrate is glucose (C6H12O6). Applying the terms defined above, glucose is a monosaccharide, an aldohexose (note that the function and size classifications are combined in one word) and a reducing sugar. The general structure of glucose and many other aldohexoses was established by simple chemical reactions. The following diagram illustrates the kind of evidence considered, although some of the reagents shown here are different from those used by the original scientists. Hot hydriodic acid (HI) wa Continue reading >>

Glucose

Glucose

This article is about the naturally occurring D-form of glucose. For the L-form, see L-Glucose. Glucose is a simple sugar with the molecular formula C6H12O6, which means that it is a molecule that is made of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. Glucose circulates in the blood of animals as blood sugar. It is made during photosynthesis from water and carbon dioxide, using energy from sunlight. It is the most important source of energy for cellular respiration. Glucose is stored as a polymer, in plants as starch and in animals as glycogen. With six carbon atoms, it is classed as a hexose, a subcategory of the monosaccharides. D-Glucose is one of the sixteen aldohexose stereoisomers. The D-isomer, D-glucose, also known as dextrose, occurs widely in nature, but the L-isomer, L-glucose, does not. Glucose can be obtained by hydrolysis of carbohydrates such as milk sugar (lactose), cane sugar (sucrose), maltose, cellulose, glycogen, etc. It is commonly commercially manufactured from cornstarch by hydrolysis via pressurized steaming at controlled pH in a jet followed by further enzymatic depolymerization.[3] In 1747, Andreas Marggraf was the first to isolate glucose.[4] Glucose is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.[5] The name glucose derives through the French from the Greek γλυκός, which means "sweet," in reference to must, the sweet, first press of grapes in the making of wine.[6][7] The suffix "-ose" is a chemical classifier, denoting a carbohydrate. Function in biology[edit] Glucose is the most widely used aldohexose in living organisms. One possible explanation for this is that glucose has a lower tendency than other aldohexoses to react nonspecific Continue reading >>

Draw The Structure Of A Glucose Molecule

Draw The Structure Of A Glucose Molecule

Since carbon is the backbone of organic molecules I suggest counting Carbon atoms first, then oxygen, and placing hydrogen in any free locations. If you know how many Carbon and Oxygen atoms are in glucose thenrememberingwhere the 12 hydrogen atoms go is like filling in the free space. The simple rules below will make drawing the structure of glucose much easier. You can review the periodic table if you want to know where I got the number of bonds from. An easy way to draw the open chain structure of glucose is to follow these 3 steps: You should only need to rememberwhichside of the chain the oxygen atoms are. If you count the number of bonds on each carbon, and count the number of bonds of each oxygen atom, you can fill in the rest of the structure with hydrogen atoms. When drawing the ring structure of glucose oranyother molecule, most of the carbons atoms are represented by a bent line. Just for technical purposes I am showing the alpha-D-glucose molecule below. This is the form of glucose used to make starches such as amylose and amylopectin that areeasilydigestible. This is the form of glucose that should be studied in most biology courses. [gn_note color=#21ab2f]The OH groups always bonds to the ring from the oxygen atom. -OH and HO- are correct but -HO is not. Remember the bonding rules above[/gn_note]. Continue reading >>

Carbohydrates - Chemical Structure

Carbohydrates - Chemical Structure

Carbohydrates consist of the elements carbon (C), hydrogen (H) and oxygen (O) with a ratio of hydrogen twice that of carbon and oxygen. Carbohydrates include sugars, starches, cellulose and many other compounds found in living organisms.In their basic form, carbohydratesare simple sugars or monosaccharides. These simple sugars can combine with each otherto form more complex carbohydrates. The combination of two simple sugars is a disaccharide.Carbohydrates consisting of two to ten simple sugars are called oligosaccharides, and thosewith a larger number are called polysaccharides. Sugars are white crystalline carbohydrates that are soluble in water and generally have a sweet taste. Monosaccharide classifications based on the number of carbons Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose Allose, Altrose, Fructose, Galactose, Glucose, Gulose, Idose, Mannose, Sorbose, Talose, Tagatose Many saccharide structures differ only in the orientation of the hydroxyl groups (-OH).This slight structural difference makes a big difference in thebiochemical properties, organoleptic properties (e.g., taste), and in the physical properties such asmelting point and Specific Rotation (how polarized light is distorted).A chain-form monosaccharide that has a carbonyl group (C=O) on an end carbon forming an aldehyde group (-CHO) is classified as an aldose.When the carbonyl group is on an inner atom forming a ketone, it is classified as a ketose. The ring form of ribose is a component of ribonucleicacid(RNA). Deoxyribose, which is missing an oxygen at position2, is a component of deoxyribonucleicacid(DNA) .In nucleic acids, the hydroxyl group attached tocarbon number1 is replaced with nucleotide bases. Hexoses, such as the ones illustrated here, have the molecular formula C6H12O6. Germ Continue reading >>

Principles Of Biochemistry/the Carbohydrates: Monosaccharides, Disaccharides And Polysaccharides

Principles Of Biochemistry/the Carbohydrates: Monosaccharides, Disaccharides And Polysaccharides

Principles of Biochemistry/The Carbohydrates: Monosaccharides, Disaccharides and Polysaccharides From Wikibooks, open books for an open world Earlier the name "carbohydrate" was used in chemistry for any compound with the formula Cm(H2O)n. Following this definition, some chemists considered formaldehyde CH2O to be the simplest carbohydrate, while others claimed that title for glycolaldehyde. Today the term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons. Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. A typical monosaccharide has the structure H-(CHOH)x(C=O)-(CHOH)y-H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group . Examples of monosaccharides are glucose , fructose, and glyceraldehyde. However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., uronic acids and deoxy-sugars such as fucose ), and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g., formaldehyde CH2O and inositol (CH2O)6). The open-chain form of a monosaccharide often coexists with a heterocyclic compound|closed ring form where the aldehyde / ketone carbonyl group carbon (C=O) and hydroxyl group (-OH) react forming a hemiacetal with a new C-O-C bridge. Monosaccharides can be linked together into what are called polysaccharides (or oligosaccharides) in a large variety of ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose, a component of DNA, is Continue reading >>

Molecular Structure Of Glucose

Molecular Structure Of Glucose

What I wanted to do in this video is familiarize ourselves with one of the most important molecules in biology And that is Glucose sometimes referred to as Dextrose and the term Dextrose comes from the fact that the form of Glucose typically Typically found in nature if you form a solution of it, it's going to polarize light to the right and Dextre means Right But the more typical term glucose this literally means sweet in greek if you ask a greek friend to say sweet it sounds like Lucas or I'm not saying it perfectly, but it sounds a lot like a glucose And that's because that's where the word comes from and it is super important because it is it is it is how energy [is] stored and transferred in biological systems in fact right [now] when if someone were to talk about your blood your blood sugar they're talking about the glucose content, so when people talk about blood blood sugar they're talking about your they're talking about your glucose content the whole process of photosynthesis this is all about plants using harnessing the [sun's] energy and storing that energy in the form of glucose when we talk about when we talk about things like respiration in our in our cells cellular respiration that's all about taking glucose and using it to full and to create atp's which are the molecular currency of energy Inside of our body, so these are in credit is an incredibly important molecule We can start wreaking chains of glucose to form Glycogen to form Starches this along with another similar another simple sugar fructose you can use to form our table sugar But even glucose by itself is sweet so let's get familiar with it as a molecule so immediately When you look at this is it kind of drawn as a as an open chain we see that we have one two three Actually, let me number thes Continue reading >>

Organic Chemistry - What Makes The Cyclic Structure Of Glucose More Stable Than The Open Chain Structure? - Chemistry Stack Exchange

Organic Chemistry - What Makes The Cyclic Structure Of Glucose More Stable Than The Open Chain Structure? - Chemistry Stack Exchange

What makes the cyclic structure of glucose more stable than the open chain structure? You get to form a C-O $\mathrm{\sigma}$ bond at the expense of a C-O $\mathrm{\pi}$ bond. The single bond has a higher bond energy, even though it is somewhat de-stabilized by the anomeric effect. It's still an overall win, despite taking the entropic hit to confine your molecule into a ring. @Karl That's not correct. The free energy difference between the open-chain and ring forms has a entropic component because the open-chain has more degrees of freedom. Zhe Oct 20 '16 at 0:48 Irrelevant was the wrong word. I meant to say that taking into account the entropic effect, it becomes temperature-dependent, and no temperature was specified. Karl Oct 20 '16 at 2:14 Shouldn't the double bond have more energy than the single bond? As far as i remember, the order of bond energy is triple>double>single.. Or am I missing something? Anindya Oct 20 '16 at 6:04 Yes, you're missing the fact that the double bond is a $\mathrm{\sigma}$ bond and a $\mathrm{\pi}$ bond. The latter has a smaller bond energy, so breaking a $\mathrm{\pi}$ bond for a $\mathrm{\sigma}$ bond if favorable in this case. In other words, two singles bonds > one double bond. Zhe Oct 20 '16 at 13:30 @Zhe "It's still an overall win, despite taking the entropic hit to confine your molecule into a ring." I am curious about how to measure this entropic difference. Mockingbird Oct 15 '17 at 17:12 Continue reading >>

Structure Of Glucose And Other Carbohydrate Molecules

Structure Of Glucose And Other Carbohydrate Molecules

Molecular structure of glucose and other carbohydrates To the right of this page I have put a number of links to other files on this website showing 3-D molecules of carbohydrates, which offer the opportunity to see and interact with these molecular models in 3 dimensions. At the bottom of the page there are also links to related topics at this level on the BioTopics website Glucose is an example of a carbohydrate which is commonly encountered. It is also known as blood sugar, and dextrose. Its chemical formula is C6H12O6, and this empirical formula is shared by other sugars - called hexoses - 6 carbon sugars. You may wish to know in some detail how these 24 atoms are arranged in the molecule of glucose the structural formula. In some books you may see diagrams of the glucose molecule looking like this: This so-called stick diagram really only describes how things are in dry (powder) glucose. In life - in your blood and inside cells of plants and animals - most of the glucose consists of molecules shaped into a ring (actually a 6-sided figure, a hexagon) which may be drawn with this fairly simple format: Note that there is an oxygen atom forming part of the ring, and that there are simple lines drawn making up the rest of the ring, and a section sticking out to one side. These lines represent carbon atoms, and -H and -OH groups, most of which have been left out for simplicity. Sometimes the details of just some of these -H and -OH gr oups are drawn in at one end (or both ends). This is because the orientation of these groups slightly alters the chemistry of the molecule, so the resulting molecules are given different names. In alpha glucose the -H group of the rightmost Carbon atom (C1) is above the plane of the ring, whereas it projects below the ring in beta glucose. Continue reading >>

Open-chain Compound - An Overview | Sciencedirect Topics

Open-chain Compound - An Overview | Sciencedirect Topics

D.O. Tymoshenko, in Comprehensive Heterocyclic Chemistry III , 2008 Open-chain vinylamine is an identifiable side product during synthesis of 1,4,7-triazacyclononanes, resulting from the side E2-elimination process. Intermediate 82 can be isolated by column chromatography on neutral alumina and subsequently converted to 2-methyl-1,6-ditosyl-1,3,6-triazocane 31 by the addition of either silica gel or HBF4. The reaction also proceeds smoothly under Lewis acid catalysis using BF3 etherate (Equation 9; <1999TL9363>). An alternative mechanism for this transformation, resulting in formation of oxadiazocanes rather than triazocanes, was proposed recently <2001EJO4233>. A novel ring system, pyrrolo[3,2-c][1,2,5]benzotriazocine 84, was synthesized using a three-step sequence (Scheme 18; <1998JHC1535>). Diazotization of amino pyrrole derivative 83 in acetic acid afforded 1,2,5-triazocine ring in 75% yield by intramolecular coupling of diazonium group with ortho-position of benzyl substituent. Reaction of amides 85 with 2-hydroxyethyl-1,2-diaminoethane in pyridine and subsequent treatment of the intermediate hydroxyl compound with POCl3 yielded the corresponding pyrimidinotriazocines 86 (Scheme 19; <1993APH253>). Intramolecular cyclization of 1-(2-aminophenylsulfonyl)-1H-pyrrole-2-acetic acid 87 gave 10H-pyrrolo[1,2-b][1,2,6]benzothiadiazocin-11(12H)-one 5,5-dioxides 88. Intermediate 87 was prepared in four steps starting from the corresponding ortho-nitrobenzenesulfonyl chlorides and ethyl 1H-pyrrole-2-(-oxo)acetate (Equation 10; <1996JHC2019>). Eight-membered N,N-protected cyclic sulfonylamide 89, bearing two different protecting groups, was demonstrated as useful intermediate for preparation of pseudopeptides. Synthesis of 89 was carried out in two steps by an intermolecular M Continue reading >>

Carbohydrates - Glucose

Carbohydrates - Glucose

Glucose is by far the most common carbohydrate and classified as a monosaccharide, an aldose, a hexose, and is a reducing sugar. It is also known as dextrose, because it is dextrorotatory (meaning that as an optical isomer is rotates plane polarized light to the right and also an origin for the D designation. Glucose is also called blood sugar as it circulates in the blood at a concentration of 65-110 mg/dL (or 65-110 mg/100 ml) of blood. Glucose is initially synthesized by chlorophyll in plants using carbon dioxide from the air and sunlight as an energy source. Glucose is further converted to starch for storage. Up until now we have been presenting the structure of glucose as a chain. In reality, an aqueous sugar solution contains only 0.02% of the glucose in the chain form, the majority of the structure is in the cyclic chair form. Since carbohydrates contain both alcohol and aldehyde or ketone functional groups, the straight-chain form is easily converted into the chair form - hemiacetal ring structure. Due to the tetrahedral geometry of carbons that ultimately make a 6 membered stable ring , the -OH on carbon #5 is converted into the ether linkage to close the ring with carbon #1. This makes a 6 member ring - five carbons and one oxygen. Steps in the ring closure (hemiacetal synthesis): 1. The electrons on the alcohol oxygen are used to bond the carbon #1 to make an ether (red oxygen atom). 2. The hydrogen (green) is transferred to the carbonyl oxygen (green) to make a new alcohol group (green). The chair structures are always written with the orientation depicted on the left to avoid confusion. Carbon # 1 is now called the anomeric carbon and is the center of a hemiacetal functional group. A carbon that has both an ether oxygen and an alcohol group is a hemiacetal Continue reading >>

Mcb 150 Frequently Asked Questions

Mcb 150 Frequently Asked Questions

Domains of Life; Prokaryotic vs. Eukaryotic Cells How does glucose go from its straight chain form to ring structure? I don't see the aldehyde group in the ring structure. Is there hydrolysis involved? Check out the lecture 3 slide that starts with the phrase Monosaccharides are typically found in lengths of 3, 5, or 6 carbons. This has the most perfect picture of a ring form of a glucose forming from a chain structure. The aldehyde is key because the carbon (number 1 carbon) of the aldehyde group interacts with the hydroxyl group attached to the 5th carbon of the carbohydrate chain. This excludes the 6th carbon from the ring, giving it its distinct 5-C, 6-member ring structure. Because the 1st carbon is now involved in a fourth covalent bond, the double-bonded oxygen from the aldehyde must become a single bond. The oxygen now has two free electrons and must form a bond with a hydrogen to form a hydroxyl group; this is why you do not see a double-bonded oxygen in the ring structure form of glucose. Even if this is not exactly the way it happens, I like to think of the hydrogen that was attached to the hydroxyl group of the 5th carbon hopping over to bind newly single-bonded oxygen of the former aldehyde group. Water is not gained or lost in this formation of a covalent bond. If you count the number of oxygens in the chain structure (6) and the ring (6), you see that none are lost. That is a good way to confirm that no waters are gained or lost if you are ever not sure. Continue reading >>

3.8: Fischer And Haworth Projections

3.8: Fischer And Haworth Projections

When reading the chemical and biochemical literature, you are likely to encounter several different conventions for drawing molecules in three dimensions, depending on the context of the discussion. While organic chemists prefer to use the dashed/solid wedge convention to show stereochemistry, biochemists often use drawings called Fischer projections and Haworth projections to discuss and compare the structure of sugar molecules. Fisher projections show sugars in their open chain form. In a Fischer projection, the carbon atoms of a sugar molecule are connected vertically by solid lines, while carbon-oxygen and carbon-hydrogen bonds are shown horizontally. Stereochemical information is conveyed by a simple rule: vertical bonds point into the plane of the page, while horizontal bonds point out of the page. Below are two different representations of (R)-glyceraldehyde, the smallest sugar molecule (also called D-glyceraldehyde in the stereochemical nomenclature used for sugars): Below are three representations of the open chain form of D-glucose: in the conventional Fischer projection (A), in the line structure variation of the Fischer projection in which carbons and hydrogens are not shown (B), and finally in the 'zigzag' style (C) that is preferred by organic chemists. Care must be taken when translating Fischer projection structures into' zigzag' format it is easy to get the stereochemistry wrong. Probably the best way to make a translation is to simply assign R/S configurations to each stereocenter, and proceed from there. When deciding whether a stereocenter in a Fischer projection is R or S, realize that the hydrogen, in a horizontal bond, is pointing towards you therefore, a counterclockwise circle means R, and a clockwise circle means S (the opposite of when the hy Continue reading >>

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