Note how the lines and the substituents hhead, ttail, ffoot clearly show the orientation. Jul 11, 2015 test your fischer projections skills with this short quiz including questions on chirality and stereochemistry, conversion of fischer to newman, sawhorse and 56 membered sugar rings. One last worksheet, and well be all done with stereochem. Determining stereochemical relationships for acyclic structures there are five different methods that can be used to determine the stereochemical relationship between acyclic molecules drawn using different threedimensional representations. So get pumpedyoure a third of the way done with o chem 1 j. In this lesson, will know how to convert a sawhorse representation into the fischer which is very important for the reaction mechanism. These become less convenient for molecules with many chiral carbon atoms, and we typically use fischer projections. Transfats are associated with increased risk of cardiovascular disease and are targeted for removal from the food supply. Fischer projections, haworth structures and chair conformers the acyclic structure of a sugar is commonly drawn as a fischer projection. Stereochemistry r and s configuration fischer and newman. Concept of chirality stereochemistry 7 h h h h h h h hh h h h h h h h h h h h h h h newman projection sawhorse projection the eclipsed conformation the staggered conformation conformations of ethane the two methyl groups in ethane are not fixed in a single positon. Redraw the given sawhorse projection such that it has an eclipsed conformation.
Stereochemistry some definitions with examples presenting stereo structures goes back in the plane of the paper comes. The bond between the two atoms is represented by a diagonal line, the lefthand bottom end of which locates the atom nearer the observer and the righthand top end the atom that is further away. It extends the list of those defined in the iupac nomenclature of organic chemistry. Draw the haworth projection so that the ring oxygen is on the top. If the hydroxyl group or amino group for amino acids is pointing to the right in the fischer projection, the sugar or amino acid is designated as d. What are sawhorse projections in organic chemistry. Stereochemistry of tetrahedral carbons, stereoisomers stereoisomers, stereocenter, chiral, enantiomers, racemic mixture, configuration of stereocenters, molecules with multiple stereocenters, tartaric acid and enantiomers. Sawhorse projections are very similar to newman projections, but are used more often because the carboncarbon bond that is compressed in a newman projection is fully drawn out in a sawhorse projection. A sawhorse projection can reveal staggered and eclipsed conformations in molecules. Sawhorse plans plans to diy a nice folding sawhorse with a shelf.
Basic terminology of stereochemistry iupac recommendations 1996 on page 2217. This will work great for larpingcamping and its easy to fold down for traveling. Relationship between objects and their mirror images symmetric objects are superposable with their mirror images. Just as with newman projections, you can draw sawhorse projections in eclipsed. It can be a horse, table legs, armour rack and more. Nov 15, 2018 mar 08, 2020 sawhorse formula into newman projection formula stereochemistry chemistry notes edurev is made by best teachers of chemistry. Main difference staggered vs eclipsed conformation. A sawhorse projection is similar to a newman projection, but it shows the carboncarbon bond that is hidden in a newman projection. You can see in the next illustration that the top carbon group of the fischer projection of 2. Test your fischer projections skills with this short quiz including questions on chirality and stereochemistry, conversion of fischer to newman, sawhorse and 56 membered sugar rings. Saw horse general organic chemistry part 22 youtube. Nov 22, 2010 if we depict it from above and a little to the side, we have what we can refer to as a sawhorse projection. These can be converted into newman projections or other structures which show 3dimensional representations of molecules.
Anita tandon university of delhi delhi 17 contents. Problem 8 draw a 3d newman projection and a sawhorse representation for each the following fischer projections. Determining stereochemical relationships for acyclic. Iupac has defined a zigzag projection as a stereochemical projection for an acyclic molecule or portion of a molecule where the main chain is represented by azigzag line in the plane and the substituents are shown above or below the plane 2. If we rotate this a little bit, well see the staggered conformation of ethane from a sawhorse perspective. When properly laidout, sawhorse projections are useful for determining enantiomeric or diasteromeric relationships between two molecules, because the mirror image or superimposibility. Learn how to view the molecule and quickly assign priority without the need to redraw into a sawhorse. The wedge and dash representations of stereochemistry can often become cumbersome, especially for large molecules which contain a number of stereocenters.
The stereochemistry of double bonds in dietary fats fatty acid esters of glycerol is important. Conversion of newman, sawhorse and fischer projection dash. Syed r hussaini department of chemistry and biochemistry. Lecture on drawing sawhorse projections for organic molecules. Even if youre not required to draw conversions on your exam, knowing how is a critical skill to truly understanding the nature of chirality in fischer projections. In the fischer projection all of the vertical lines go back into the paper and the horizontal bonds come out toward. This is especially applicable and used mostly for drawing sugars. The front carbon atom is called proximal, while the back atom is called distal. Relationship between symmetry and chirality asymmetric objects are chiral symmetric objects are achiral 2. Fischer projection introduction video khan academy. You have to remember this method because the structure looks flat. The front carbon is not written but is located at the. Newman and saw horse projection and wedge representation. Stereochemistry subtle differences in spatial arrangements.
Sawhorse projection formula in sawhorse projection formula a side view of the molecule is taken. Sawhorse projections are the normal line structure molecules drawn usually without hydrogens. So the mirror method works the best when youre working with fischer projections. In a sawhorse projection, a molecule is viewed from an angle, rather than sideon. Sawhorse plans sawhorse plans, easy woodworking projects. Stereochemistry part i monday problem questions 03. Carbohydrates and amino acids are designated as d or l according to the stereochemistry of the highest numbered carbon in the fischer projection. In this video we explained interconversion of fischer projection and dash and wedge formula. In both cases, two specific carbon atoms and their connecting bond are the center of attention. This process is very similar to the method for converting sawhorse projections into fischer projections.
Introduction to stereochemistry structural constitutional isomers compounds of the same molecular formula with different connectivity structure, constitution conformational isomers compounds of the same structure that differ in rotation around one or more single bonds configurational isomers or stereoisomers compounds of the same structure that differ in one or more. In this lesson, will learn how to convert a fischer representation into the sawhorse which is also important for the reaction mechanism. Fischer and zigzag projections is described in this article. Groups connected to both the front and back carbons are drawn using sticks at 120 angles. Converting between sawhorse and fischer projections is a critical skill in understanding your chiral molecules. Compounds that are superimposable with their mirror image are called achiral.
Manipulate the fischer projection so this hydroxyl group is on the bottom. H br ch 3 h h h br c3 h 3 r i ii iii a i b ii c iii d it does not have a non superposable enantiom er. Isomerism and stereochemistry answers to worked examples we 18. This video teaches you how to quickly find configurations of molecules presented in a newman projection. This is a glossary of the more important, and most widelyused, stereochemical terms. In organic chemistry, subtle differences in spatial arrangements can give rise to prominent effects. This is true onlyifweareconcernedwiththe relative stereochemistry.
Notice that when drawing the newman projection of the eclipsed conformation of ethane, you cannot clearly draw the rear hydrogens exactly behind the front ones. If the given sawhorse projection is staggered, it can be. Find the chiral centers, assign the priorities and make your assignments. Levorotatory compound that rotates plane polarized light counterclockwise figure 1. Substituents on the right side of the fischer projection will be on the bottom face of the haworth. This diagram style is an alternative to a sawhorse projection, which views a carboncarbon bond from an oblique angle, or a wedgeanddash style, such as a natta projection. The sawhorse or newman representations of 2butanol, \5a\ and \5b\ and \6a\ and \6b\, are excellent for showing the arrangements of the atoms in conformations, but are needlessly complex for representing the stereochemical configuration. Use hands or model atoms to help you see these configurations whenever the low priority group is. It explains how to assign r and s configurations to the chiral centers in a fischer projection. An alternative way to represent stereochemistry is the fischer projection, which was first used by the german chemist emil fischer.
Each method has its own advantages, depending upon the circumstances. Stereochemistry the branch of chemistry concerned with the threedimensional arrangement of atoms and molecules and the effect of this on chemical reactions. Draw a newman projection along any of the c c bonds in cyclopropane. Molecules, therefore, want to have a low strain structure. Apr 24, 2018 this organic chemistry video tutorial provides a basic introduction into stereochemistry. Video 7 finding r and s configurations for nontraditional molecules can be somewhat tricky. Dextrorotatory compound that rotates plane polarized light clockwise figure 1. In the fischer projection all of the vertical lines go back into the paper and the horizontal bonds come out toward you.
Basic terminology of stereochemistry iupac recommendations 1996 abstracr. Fischer projections are just another way of drawing compounds contacting chirality centers. Stereochemistry an introduction pdf 40p this note covers the following topics. In other words, it is the name given for different positions that a molecule can be bent into. This type of representation clearly illustrates the specific dihedral angle between the proximal and distal atoms. The newman projection is viewed on a line from the front carbon to the back carbon. So lets watch the video and look at the different conformations of ethane.
C br h h c cl h br hcl c h h br cl h h br cl 2d drawing. In my opinion, you should get a model set and figure out a method that works the best for you. Sawhorse plans the within track on troublefree programs of cool outdoor woodworking inspiration. In a sawhorse projection, the backbone carbons are represented by a diagonal line, and the terminal carbons are shown in groups, just as in the fischer projection. A newman projection, useful in alkane stereochemistry, visualizes the conformation of a chemical bond from front to back, with the front atom represented by a dot and the back carbon as a circle. Finally, lets draw the enantiomer of this compound. The remaining bonds are projected on paper by small lines drawn out from the terminal ends of the diagonal line. Stereochemistry an introduction pdf 40p download book. Interconversion of fischer and zigzag projections learning. How to converting newman projection to fischer projection stereochemistry. Partially hydrogenated cooking oils are the primary source of transfats. And this trick should always work when youre working with fischer projections. The authors method is suitable for the correct representation of absolute stereochemistry as well. Pdf conformational analysis is one of the significant subjects in the organic chemistry curriculum.
Such a sawhorse projection must be drawn directly from a fischer projection without any rotation. Use the sawhorse projection to draw a stepwise mechanism leading to the major product. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. This document is highly rated by chemistry students and has been viewed 174 times. Using the sawhorse projection, convert this fischer projection to the corresponding natta projection and assign all stereocentres. This projection allows rotation of the sawhorse axis so the atom or group of lowest rank can be placed at the bottom, thus allowing the point of view to be always from the top, or front, of the projection. Use hands or model atoms to help you see these configurations whenever the low priority group is facing towards you the wrong way. Newman projections are one way to look at the conformation of a noncyclical molecule. Stereochemistry is the chemistry which deals with the different arrangement of atoms or. O ho ph a ho 2 c b ph o ho c ph h d oh ph strategy. Sawhorse projections are very similar to newman projections, but are used more often because the carboncarbon bond that is compressed in a newman. I call it the sawhorse because, well, it resembles one. Structure and conformational analysis of simple alkanes.
Each type of structure allows a different perspective on the molecule. If we depict it from above and a little to the side, we have what we can refer to as a sawhorse projection. Which of the following is the enantiomer of the following substance. Mar 08, 2020 sawhorse formula into newman projection formula stereochemistry chemistry notes edurev is made by best teachers of chemistry. They are free to rotate about the single bond connecting the. Optically active optically active compounds rotate plane polarized light figure 1. Fischer projection practice problem set with solutions. In sawhorse projection formula a side view of the molecule is taken. These other styles can indicate the bonding and stereochemistry, but not as much conformational detail.
A sawhorse projection is a view of a molecule down a particular carboncarbon bond. They were initially proposed by emil fischer for making it easier to draw the structures of compounds containing multiple chirality centers with the main idea of not having to draw the wedge and dash lines for every single chiral center. Representation of organic structure chemistry libretexts. Introduction to stereochemistry compounds that are not superimposable with their mirror image are called chiral in greek, chiral means handed 3methylhexane is a chiral molecule. Finally, the steps on changing a sawhorse projection into a fischer projection will be given. Difference between staggered and eclipsed conformation. Just as with newman projections, you can draw sawhorse projections in eclipsed and. Now, an alternative way to depict conformations is the fronton view. Now consider the stereochemistry in the reaction b. The term conformation describes different forms of projections of a molecule. You should be prepared to sketch various conformers using both sawhorse representations and newman projections. The newman projection and the sawhorse projection are used to depict specific conformers or to distinguish vicinal stereochemistry. The two carbon atoms are joined by a larger diagonal line which is taken to be on the plane of the paper. R and s nomemclature problem 3 classify the absolute configuration of all chiral centers as r or s in the molecules below.
Fischer projection to the opposite sides of the zigzag backbone can provide the correct zigzag structure. Fischer projections with practice problems chemistry steps. Sawhorse projections sawhorse projections are very similar to newman projections, but are used more often because the carboncarbon bond that is compressed in a newman projection is fully drawn out in a sawhorse projection. Before we begin our exploration of stereochemistry and chirality, we first need to consider the subject of conformational isomerism, which has to do with rotation about single bonds we learned in section 2. Consider the carbonoxygen bond in ethanol, for example. For example, imagine looking at model 1 of ethane below at an angle so that the carbon atom highlighted in red is further from you, and the carbon atom in grey is closer to you.
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