How Many Chiral Carbons In Cyclic Glucose

Stereochemistry - Why Is It Important That Glucoses Third Oh Group Points To The Left? - Chemistry Stack Exchange

Why is it important that glucoses third OH group points to the left? My question pertains to the location of the OH group on the 3rd carbon in a glucose molecule. If atoms can rotate freely around single bonds, then why is this important? Why can't glucose be drawn with 'all H on the left'? This is the concept called stereochemistry. Each carbon with 4 bonds has an approximately tetrahedral geometry. We assign a configuration to the situation by numbering the substituents in terms of priority. Hydrogen is lowest. Oxygen is highest. The top carbon is second, and the other carbon is third. We then trace a route from 1 to 2 to 3. This would be a clockwise circle, and we would call this configuration S. If we switched sides between the H and the O we would follow this circle widdershins and call the configuration R. So the substituents can't be exchanged because the configuration would change. When there is only one of these tetrahedral centers (called stereocenters) in play for a situation, it does not matter at all which one you have. But the moment a second stereocenter comes into the picture, chemical properties begin to change. A fairly tractable analogy is feet and shoes. When you aren't wearing shoes, your left foot and your right foot are about the same. But when you try to put shoes on, putting the right shoe on the left foot is slightly more difficult than putting the right shoe on the right foot. In this loose analogy, the 'reaction' of putting your shoes on is slowed based on how the stereocenters of foot and shoe interact. Onto glucose ... Because there are 4 stereocenters in glucose, it has a distinct shape from its isomers. The other chemicals in your body also have their own shapes/configurations. Glucose reacts slightly differently than other sugars in the Continue reading >>

Lecture 23

Carbohydrates are polyhydroxy aldehydes and ketonesor compounds that can be hydrolyzed to form them, asshown below. Carbohydrates include sugars, starches, cellulose and other substancesfound in plants. During photosynthesis, plants converts atmosphericcarbon dioxide and water into carbohydrates and oxygen: This is a non-spontaneous process D G > 0). Solar energyis captured and converted to chemical energy. The photosyntheticprocess reduces the carbon in CO2 (C = +4). These reduced compounds store chemical energy in their bonds. Animals that eat these reduced carbon compounds release thisstored energy in the oxidative metabolic process: This process is spontaneous (DG < 0). Carbohydrates provideenergy and carbon atoms for the biochemical reactionsin the body. Carbohydrates are classified into two groups - simple andcomplex. Simple carbohydrates are monosaccharides,like glucose and fructose, that can not be hydrolyzed (brokendown) into smaller molecules. Complex carbohydrates are composedof two or more monosaccharides. Disaccharides, like lactoseor sucrose, contain two monosaccharides. Polysaccharides,like cellulose, can be made up of thousands of monosaccharideslinked together. We will start by studying monosaccharides. Monosaccharidescan be classified according to the number of carbon atoms theycontain and the type of carbonyl group (C=O) they contain,either aldehyde or ketone. The suffix "-ose"indicates that a compound is a carbohydrate. The prefixes "aldo"or "keto" characterize the C=O, and "tri",tetr", "pent" or "hex" indicate the numberof carbon atoms. I is an aldose since the carbonyl group is an aldehydefunction. It is a 4 carbon compound so it would be classifiedas an aldotetrose. The carbonyl group in II is a ketonefunction, so it will be a ketose. It is a six Continue reading >>

Bch 4053 Biochemistry I

. "Simple sugars" with the formula (C H2O)n. The word carbohydrate refers to the fact that this class of molecules consists of hydrates of carbon. . Polymeric molecule of sugar comprising 2-10 covalently linked monosaccharide units. Often found conjugated to other classes of biomolecules including lipids and proteins. . Larger polymers of simple sugars. On the order of hundreds to thousands of monosaccharide units as linear or branched polymers. The number of carbons, and the functional group, are specified in the nomenclature for monosaccharides. The letters "ul" are sometimes inserted into the name (rather than the word "keto") to indicate the monosaccharide is a ketose. In addition to the general name of the monosaccharide, the stereochemistry about each chiral center is important. We need a way to specify both the chirality and the particular carbon in the monosaccharide molecule for each chiral center We need a convenient way to represent such stereochemical features when drawing monosaccharides Fischer projection method of drawing such molecules The carbonyl group of the keto or aldose functional group is considered to be closest to the "start" of the carbon chain. The carbon thus identified as the "first" carbon in the chain is carbon #1. The remaining carbons are numbered sequentially. The "highest numbered" asymmetric carbon (i.e. furthest from the "start" carbon) determines whether the monosaccharide is the "D" or "L" isomer. In Fischer Projections, the "D" isomer will have the hydroxyl (-OH) functional group located on the right-hand side of the chiral C. Note that the D/L nomenclature has nothing to do with optical rotation activity of the structure; this is indicated by the use of (+) or (-). The majority of saccharides in nature have the "D" isomer Common Continue reading >>

Chemistry: The Central Science, Chapter 25, Section 10

Carbohydrates are an important class of naturally occurring substances found in both plant and animal matter. The name carbohydrate (hydrate of carbon) comes from the empirical formulas for most substances in this class; they can be written as Cx(H2O)y. For example, glucose, the most abundant carbohydrate, has the molecular formula C6H12O6, or C6(H2O)6. Carbohydrates are not really hydrates of carbon; rather, they are polyhydroxy aldehydes and ketones. For example, glucose is a six-carbon aldehyde sugar, whereas fructose, the sugar that occurs widely in fruit, is a six-carbon ketone sugar (Figure 25.24). Figure 25.24 Linear structures of glucose and fructose. Glucose, having both alcohol and aldehyde functional groups and having a reasonably long and flexible backbone, can react with itself to form a six-member-ring structure, as shown in Figure 25.25. Indeed, only a small percentage of the glucose molecules are in the open-chain form in aqueous solution. Although the ring is often drawn in a planar form, the molecules are actually nonplanar. Figure 25.25 Glucose reacts with itself to form two six-member-ring structures, designated During formation of the ring structure of glucose, the functional groups on carbons 1 and 5 can take up alternative relative orientation. In the form the OH group on carbon 1 and the CH2OH group on carbon 5 point in opposite directions. In the form the OH on carbon 1 and the CH2OH on carbon 5 point in the same direction. Although the difference between the forms might seem small, it has enormous biological consequences. As we will soon see, this one small change in structure accounts for the vast difference between starch and cellulose. Fructose can cyclize to form either five- or six-member rings. The five-member ring forms when the OH grou Continue reading >>

How Is Glucose Having 4 Chiral Centres?

H-C=O |H-C-OH |OH-C-H | H- C-OH |H- C -OH |H- C-OH | HThe bonding lines are attached basically with Carbon here in computer they are all being shown on left side with OH and H but consider tham all under carbon I have made above... show more H-C=O The bonding lines are attached basically with Carbon here in computer they are all being shown on left side with OH and H but consider tham all under carbon I have made above the structure of glucose but how come are there four chiral centres plzz explain me in detail.. Are you sure you want to delete this answer? Best Answer: A chiral centre happen when a carbon atom is attached tetrehedrally to 4 different atoms/groups. There are 4 such atoms in the glucose molecule. Refer to the link provided, the carbon atoms with "star" are the chiral centres. Yeah, what Nam said is correct, but if you look at your bottom carbon, it can be written as CH2OH. I'm assuming you are probably aware of what a chiral centre is; one of the easiest ways of determining a chiral centre is if there are 4 different functional groups surrounding it. As soon as there are 2 hydrogens, or a carbonyl group, you carbon centre will not be chiral. You have drawn a Fischer projection, and personally I can't stand them because sugars exist in a cyclic structures (either pentose or hexose formations), with an alcohol from the 4th or 5th carbon condensing readily with the aldehyde. In the cyclic pyranose formation, there are 5 chiral carbons, but with furanose formation, there are 4 chiral carbons. Upload failed. Please upload a file larger than 100x100 pixels We are experiencing some problems, please try again. You can only upload files of type PNG, JPG, or JPEG. You can only upload files of type 3GP, 3GPP, MP4, MOV, AVI, MPG, MPEG, or RM. You can only upload ph Continue reading >>

Chirality And Stereoisomers

Stereoisomers are isomers that differ in spatial arrangement of atoms, rather than order of atomic connectivity. One of their most interesting type of isomer is the mirror-image stereoisomers, a non-superimposable set of two molecules that are mirror image of one another. The existence of these molecules are determined by concept known as chirality . Organic compounds, molecules created around a chain of carbon atom (more commonly known as carbon backbone), play an essential role in the chemistry of life. These molecules derive their importance from the energy they carry, mainly in a form of potential energy between atomic molecules. Since such potential force can be widely affected due to changes in atomic placement, it is important to understand the concept of an isomer , a molecule sharing same atomic make up as another but differing in structural arrangements. This article will be devoted to a specific isomers called stereoisomers and its property of chirality (Figure 1). Figure 1: Two enantiomers of a tetrahedral complex. The concepts of steroisomerism and chirality command great deal of importance in modern organic chemistry , as these ideas helps to understand the physical and theoretical reasons behind the formation and structures of numerous organic molecules, the main reason behind the energy embedded in these essential chemicals. In contrast to more well-known constitutional isomerism, which develops isotopic compounds simply by different atomic connectivity, stereoisomerism generally maintains equal atomic connections and orders of building blocks as well as having same numbers of atoms and types of elements. What, then, makes stereoisomers so unique? To answer this question, the learner must be able to think and imagine in not just two-dimensional images, Continue reading >>

Biochem Sugars Flashcards | Quizlet

Ketoses have one fewer ______ _______ than aldoses. how many chiral centers does ribose have? how many chiral centers does fructose have? Sugars that differ at only one chiral center. (example: glucose and mannose) L-glucose and D-glucose are __________ of each other The linear and cyclic forms of a sugar are in ________________ with each other. general term for a cyclized 5 carbon sugar If the only difference between 2 sugars is the position of the OH group on the most oxidized carbon, then they are ___ of each other. a cyclic monosaccharide with OH group below ring at anomeric carbon is (alpha or beta) a cyclic monosaccharide with OH group above ring at anomeric carbon is (alpha or beta) a structural formula using bonds of different thicknesses to indicate 3-D orientation is a ___________ projection The anomeric carbon of a cyclized aldose is C__. The anomeric carbon of a cyclized ketose is C__. For all the D-enantiomers of aldoses, the CH2OH group (on C-6) projects {above OR below} the ring. name a D-glucose cyclized into a beta anomer name a D-ribose cyclized into 5-sided ring as an alpha anomer A cyclized sugar will have an additional _______ ______ at C1 (compared to the linear structure). In maltose, the first cyclized glucose is named alpha/beta-D/L- _______________. In the alpha anomer of lactose, the second cyclized sugar is named _____-__-_____________. The glycosidic linkage 1-->2 is found between an aldose and a ketose. true or false A _________ sugar, even when cyclized, can open up on one end to yield a free C=O group. __________ reagent reacts with reducing sugars to form a red precipitate (copper oxide). Continue reading >>

Structural Biochemistry/carbohydrates/monosaccharides

Structural Biochemistry/Carbohydrates/Monosaccharides Monosaccharides are the simplest form of carbohydrates and may be subcategorized as aldoses or ketoses . The sugar is an aldose if it contains an aldehyde functional group. A ketose signifies that the sugar contains a ketone functional group. Monosaccharides may be further classified based on the number of carbon atoms in the backbone, which can be designated with the prefixes tri-(3), tetr-(4), pent-(5), hex-(6), hept-(7), etc. in the name of the sugar. Monosaccharides are often represented by a Fischer Projection, a shorthand notation particularly useful for showing stereochemistry in straight chained organic compounds. The L and D confirmations represent the absolute configuration of the asymmetric carbon farthest away from the ketone or aldehyde group on the monosaccharide. On the Fischer projection, if the farthest hydroxyl(-OH) group is on the right, then it is classified as D sugar, if the hydroxyl group is on the left, then it is a L sugar. Enantiomers, Diastereoisomers(anomerism), and Epimers[ edit ] Example of Diastereomers. The areas marked blue indicate the differing stereogenic centers. Example of an Enantiomer. The blue indicates the D-isomer and the red indicates the L-isomer Due to the fact that carbohydrates contain multiple stereocenters, many isomers are possible including enantiomers, diastereoisomers, and epimers. Two carbohydrates are said to be enantiomers if they are nonsuperimposable mirror images of one another. An example of an enantiomer is the D and L isomers of glucose, as shown by the figure to the right. A second type of isomer seen in carbohydrates are diastereoisomers. Carbohydrates are classified as diastereomers if their chiral carbons are connected to the exactly the same substra Continue reading >>

Chapter 25 Notes

D-glucose has 4 chiral carbon atoms (24 = 16 possible stereoisomers) the name D-glucose implies just one of those stereoisomers one stereoisomer is the enantiomer of D-glucose the other 14 stereoisomers are diastereomers of D-glucose the reference for D & L designation of stereochemistry write all chiral centers in Fischer projections pentoses: 4 pairs of stereoisomers (including D-ribose) hexoses: 8 pairs of stereoisomers (including D-glucose) a method to depict ring structures (flat) arrange the ring with O in the back (or back-right) an OH to the right (Fischer) is down (Haworth) an OH to the left (Fischer) is up (Haworth) D-sugars will have the last CH2OH group up the new hemiacetal could have either configuration the two stereoisomers at the hemiacetal (anomeric) carbon anomers are diastereomers (different physical properties) starting with either one, a mixture results in solution actual structure of glucose in solution is about 64% beta, 36% alpha, <1% open-chain beta-D-glucose has every substituent equatorial (most stable) hemiacetals to acetals with alcohol + acid (an acetal, rather than a hemiacetal, is called a glycoside) OH groups to esters with acetic anhydride OH groups to ethers with methyl sulfate (+ base such as NaH ) reduction of the carbonyl with NaBH4 (polyalcohol is called an alditol) oxidation of aldehydes to carboxylic acids with Tollen's reagent (polyhydroxy carboxylic acid is called an aldonic acid) oxidation of aldehydes and primary alcohol (both ends) to acids with HNO3 (polyhydroxy dicarboxylic acid is called an aldaric acid) acetals do not interconvert with the open-chain form glycoside linkages are used to connect sugars to other biomolecules, including other sugars or nucleic acid bases sugars that react positively with Tollen's reagent ( Continue reading >>

Doctors' Notes: Researchers link hotter weather to gestational diabetes

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 >>

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 >>

Chiral Center: Answers

To find whether an atom in an organic molecule is chiral or achiral use the following flow chart. If two or more ligands on a tetrahedral atom in a molecule form a ring, to determine whether they are different or not, use the following procedure. Two of the ligands on C-1 in 1 are a hydrogen atom and a methyl group. The other two ligands form a ring. To determine whether they are identical or not, convert them to two hypothetical ligands: Step 1: Number the rest of the carbon atoms in the ring for identification purposes in any way you wish. Step 2: Break the bond connecting C-1 and C-6. Step 3: The bond broken in Step 2 connected C-6 to a carbon atom (C-1). Therefore, connect C-6 to a C atom that bears no ligands. Step 4: Break the bond connecting C-1 and C-2 in 1. Step 5: The bond broken in Step 4 connected C-2 to a carbon atom (C-1). Therefore, connect C-2 to a C atom that bears no ligands. Hypothetically, the four ligands on C-1 in 1 are as follow. Notice that the two ligands that form the ring are identical. Thus, the four ligands on C-1 in 1 are not different. i. The chiral centers are marked with a red asterisk. ii. The chiral centers are marked with a red asterisk. Continue reading >>

D And L Sugars Master Organic Chemistry

What differentiates D-glucose from L-glucose ? Or D-alanine from L-alanine? Whats this D- and L- nomenclature, anyway? For everyone in a rush, here is the quick and dirty answer: For a sugardrawn in the Fischer projection with the most oxidized carbon at the top: if the OH on the bottom chiral centre points to the right, it is referred to as D- if the OH on the bottom chiral centre points to the left, it is referred to as L- . This terminology can also be applied to amino acids: see L- and D- alanine in the picture above. You might justifiably ask: dont we already have a system for assigning absolute configuration [the Cahn-Ingold-Prelog rules (i.e. R andS) ]? Why do we need a new system? The D-L system isnt a new system, folks. Its theold system it predates Cahn-Ingold-Prelog. The D-L system is literally a remnant of the horse-and-buggy era, dating backto Emil Fischers work on carbohydrates in the late 1800s a time when organic chemists had no way to determine the absolute configuration of stereocenters, which only became possible in 1951( thx, Bijvoet ). So why does it still get used? Shouldnt it be consigned to the dustbin of history, along with slide rules,8-track cassettes, and 5 floppy disks? Well, there are thriving communities in parts of rural America where horse-drawn carriages persist if you know where to look. (Maybe somedaythere will be communes where people only use 1970s and 1980s computer technology?) Likewise there is a pocket of organic chemistry where D-L system still finds use, and that is specifically in the realm of sugars and amino acids. This not a revolt by Amish chemistsagainst the modern evils of the CIP system, by the way. There are at least 3 good reasons, in the specific case of sugars and amino acids, for using L- and D- : Brevity.D-gluco Continue reading >>

Monosaccharides

Last time we learnedhow a chiral compound's absolute configuration can be described by theR/Snaming system. We also considered the situations which can arise when acompound has two (or more) stereogenic carbons. Our examples for that werein fact sugars; monosaccharide aldotetroses. We'll begin by making somestructural sense of those terms. Sugars are small molecules which belong to the class of carbohydrates.As the name implies, a carbohydrate is a molecule whose molecular formulacan be expressed in terms of just carbon and water. For example, glucosehas the formula C6(H2O)6 and sucrose (tablesugar) has the formula C6(H2O)11. Morecomplex carbohydrates such as starch and cellulose are polymers of glucose.Their formulas can be be expressed as Cn(H2O)n-1.We'll look at them in more detail next time. The difference between a monosaccharide and a disaccharide can be seenin the following example: A quick glance tells us that a monosaccharide has just one ring, a disaccharidehas two, and a polysaccharide has many. Beyond that, though, there's anotherimportant structural feature. Look at the disaccharide and focus on theoxygen which links the two rings together. The atom above it is connectedto two oxygens, both of which are in ether-type situations. The carbonand these oxygens are in an acetal linkage.(The bonds are heavier and in blue.) If we look at the corresponding location in the monosaccharide and askwhat the functional group might be, we see that it is a hemiacetal .(Here the bonds are heavier and in red.) So, another way to describe thesituation is that a monosaccharide has a single ring with a hemiacetalin it, a disaccharide has two rings linked by an acetal functional group,and a polysaccharide has many rings linked by many acetal functional groups.( Check this last Continue reading >>

Chapter 11 : Carbohydrates

Carbohydrates are the most abundant biomolecules on earth.Each year, photosynthesis by plants and algae converts more than100 billion metric tons of CO O into cellulose and otherplant products. Certain carbohydrates (sugar and starch) are astaple of the human diet in most parts of the world, and theoxidation of carbohydrates is the central energy-yielding pathwayin most nonphotosynthetic cells. Insoluble carbohydrate polymersserve as structural and protective elements in the cell walls ofbacteria and plants and in the connective tissues and cell coatsof animals. Other carbohydrate polymers lubricate skeletal jointsand provide adhesion between cells. Complex carbohydratepolymers, covalently attached to proteins or lipids, act assignals that determine the intracellular location or themetabolic fate of these glycoconjugates. This chapter introducesthe major classes of carbohydrates and glycoconjugates, andprovides a few examples of their many structural and functionalroles. Carbohydrates are polyhydroxy aldehydes or ketones, orsubstances that yield such compounds on hydrolysis. Mostsubstances of this class have empirical formulas suggesting thatthey are carbon "hydrates," in which the ratio of C : H: O is 1: 2 : 1. For example, the empirical formula of glucose isC . Althoughmany common carbohydrates conform to the empirical formula(CH , others do not; some carbohydrates also contain nitrogen,phosphorus, or sulfur. There are three major size classes of carbohydrates:monosaccharides, oligosaccharides, and polysaccharides (the word"saccharide" is derived from the Greek sakkharon,meaning "sugar"). Monosaccharides, or simple sugars,consist of a single polyhydroxy aldehyde or ketone unit. The mostabundant monosaccharide in nature is the sixcarbon sugar Oligosaccharides consist Continue reading >>