I call it the sawhorse because, well, it resembles one. Just as with newman projections, you can draw sawhorse projections in eclipsed. Dextrorotatory compound that rotates plane polarized light clockwise figure 1. In my opinion, you should get a model set and figure out a method that works the best for you. Lecture on drawing sawhorse projections for organic molecules. When properly laidout, sawhorse projections are useful for determining enantiomeric or diasteromeric relationships between two molecules, because the mirror image or superimposibility. Isomerism and stereochemistry answers to worked examples we 18. This is a glossary of the more important, and most widelyused, stereochemical terms. Representation of organic structure chemistry libretexts. 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.
And this trick should always work when youre working with fischer projections. Draw the haworth projection so that the ring oxygen is on the top. So lets watch the video and look at the different conformations of ethane. Fischer projections are just another way of drawing compounds contacting chirality centers. In a sawhorse projection, a molecule is viewed from an angle, rather than sideon. In the fischer projection all of the vertical lines go back into the paper and the horizontal bonds come out toward. In other words, it is the name given for different positions that a molecule can be bent into. Converting between sawhorse and fischer projections is a critical skill in understanding your chiral molecules. Dec 15, 2015 chirality stereochemistry video series. Mar 08, 2020 sawhorse formula into newman projection formula stereochemistry chemistry notes edurev is made by best teachers of chemistry. Optically active optically active compounds rotate plane polarized light figure 1.
The front carbon is not written but is located at the. 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. Sawhorse plans the within track on troublefree programs of cool outdoor woodworking inspiration. 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. 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. Sawhorse projection formula in sawhorse projection formula a side view of the molecule is taken. 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. Sawhorse plans sawhorse plans, easy woodworking projects. R and s nomemclature problem 3 classify the absolute configuration of all chiral centers as r or s in the molecules below. 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. Each type of structure allows a different perspective on the molecule. In this lesson, will learn how to convert a fischer representation into the sawhorse which is also important for the reaction mechanism. Transfats are associated with increased risk of cardiovascular disease and are targeted for removal from the food supply. A sawhorse projection can reveal staggered and eclipsed conformations in molecules.
Redraw the given sawhorse projection such that it has an eclipsed conformation. Stereochemistry of tetrahedral carbons, stereoisomers stereoisomers, stereocenter, chiral, enantiomers, racemic mixture, configuration of stereocenters, molecules with multiple stereocenters, tartaric acid and enantiomers. The remaining bonds are projected on paper by small lines drawn out from the terminal ends of the diagonal line. Conversion of newman, sawhorse and fischer projection dash. Groups connected to both the front and back carbons are drawn using sticks at 120 angles.
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 become less convenient for molecules with many chiral carbon atoms, and we typically use fischer projections. Use hands or model atoms to help you see these configurations whenever the low priority group is facing towards you the wrong way. 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. Molecules, therefore, want to have a low strain structure. 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. Find the chiral centers, assign the priorities and make your assignments. Apr 24, 2018 this organic chemistry video tutorial provides a basic introduction into stereochemistry. These other styles can indicate the bonding and stereochemistry, but not as much conformational detail. Newman and saw horse projection and wedge representation. A sawhorse projection is a view of a molecule down a particular carboncarbon bond. 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.
The newman projection and the sawhorse projection are used to depict specific conformers or to distinguish vicinal stereochemistry. Main difference staggered vs eclipsed conformation. Which of the following is the enantiomer of the following substance. Problem 8 draw a 3d newman projection and a sawhorse representation for each the following fischer projections. Levorotatory compound that rotates plane polarized light counterclockwise figure 1. Stereochemistry part i monday problem questions 03. Draw a newman projection along any of the c c bonds in cyclopropane. This type of representation clearly illustrates the specific dihedral angle between the proximal and distal atoms. Stereochemistry is the chemistry which deals with the different arrangement of atoms or. The authors method is suitable for the correct representation of absolute stereochemistry as well.
Fischer projections with practice problems chemistry steps. It extends the list of those defined in the iupac nomenclature of organic chemistry. Just as with newman projections, you can draw sawhorse projections in eclipsed and. If the given sawhorse projection is staggered, it can be. This document is highly rated by chemistry students and has been viewed 174 times. Compounds that are superimposable with their mirror image are called achiral. Stereochemistry an introduction pdf 40p this note covers the following topics. Substituents on the right side of the fischer projection will be on the bottom face of the haworth. This process is very similar to the method for converting sawhorse projections into fischer projections. And, believe it or not, this wraps up all of the material that will be covered on the first exam. 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 the sawhorse projection to draw a stepwise mechanism leading to the major product. The front carbon atom is called proximal, while the back atom is called distal. You can see in the next illustration that the top carbon group of the fischer projection of 2.
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. One last worksheet, and well be all done with stereochem. 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. 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. In organic chemistry, subtle differences in spatial arrangements can give rise to prominent effects. This is true onlyifweareconcernedwiththe relative stereochemistry. 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. An alternative way to represent stereochemistry is the fischer projection, which was first used by the german chemist emil fischer. The two carbon atoms are joined by a larger diagonal line which is taken to be on the plane of the paper. Difference between staggered and eclipsed conformation. Partially hydrogenated cooking oils are the primary source of transfats. In this video we explained interconversion of fischer projection and dash and wedge formula.
Stereochemistry the branch of chemistry concerned with the threedimensional arrangement of atoms and molecules and the effect of this on chemical reactions. Learn how to view the molecule and quickly assign priority without the need to redraw into a sawhorse. Here we have the staggered conformation of ethane, looking at it from a wedge and dash perspective. Saw horse general organic chemistry part 22 youtube. 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.
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. Now consider the stereochemistry in the reaction b. You have to remember this method because the structure looks flat. C br h h c cl h br hcl c h h br cl h h br cl 2d drawing. 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. 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.
Sawhorse projections are the normal line structure molecules drawn usually without hydrogens. This is especially applicable and used mostly for drawing sugars. The term conformation describes different forms of projections of a molecule. In the fischer projection all of the vertical lines go back into the paper and the horizontal bonds come out toward you. Each method has its own advantages, depending upon the circumstances. Anita tandon university of delhi delhi 17 contents. Fischer projection practice problem set with solutions. Using the sawhorse projection, convert this fischer projection to the corresponding natta projection and assign all stereocentres. 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.
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. Structure and conformational analysis of simple alkanes. In both cases, two specific carbon atoms and their connecting bond are the center of attention. A sawhorse projection is similar to a newman projection, but it shows the carboncarbon bond that is hidden in a newman projection. Manipulate the fischer projection so this hydroxyl group is on the bottom. Video 7 finding r and s configurations for nontraditional molecules can be somewhat tricky. Fischer and zigzag projections is described in this article. You should be prepared to sketch various conformers using both sawhorse representations and newman projections. Relationship between symmetry and chirality asymmetric objects are chiral symmetric objects are achiral 2. Basic terminology of stereochemistry iupac recommendations 1996 on page 2217. Fischer projection to the opposite sides of the zigzag backbone can provide the correct zigzag structure. The wedge and dash representations of stereochemistry can often become cumbersome, especially for large molecules which contain a number of stereocenters.
Stereochemistry an introduction pdf 40p download book. Determining stereochemical relationships for acyclic. How to converting newman projection to fischer projection stereochemistry. Use hands or model atoms to help you see these configurations whenever the low priority group is. 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. Basic terminology of stereochemistry iupac recommendations 1996 abstracr. O ho ph a ho 2 c b ph o ho c ph h d oh ph strategy. They are free to rotate about the single bond connecting the. Fischer projections, haworth structures and chair conformers the acyclic structure of a sugar is commonly drawn as a fischer projection.
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. Note how the lines and the substituents hhead, ttail, ffoot clearly show the orientation. Sawhorse plans plans to diy a nice folding sawhorse with a shelf. So get pumpedyoure a third of the way done with o chem 1 j. Stereochemistry some definitions with examples presenting stereo structures goes back in the plane of the paper comes. The newman projection is viewed on a line from the front carbon to the back carbon. Fischer projection introduction video khan academy. In sawhorse projection formula a side view of the molecule is taken. It explains how to assign r and s configurations to the chiral centers in a fischer projection. In this lesson, will know how to convert a sawhorse representation into the fischer which is very important for the reaction mechanism. 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. Newman projections are one way to look at the conformation of a noncyclical molecule.
Sawhorse projections are very similar to newman projections, but are used more often because the carboncarbon bond that is compressed in a newman. Syed r hussaini department of chemistry and biochemistry. Stereochemistry r and s configuration fischer and newman. 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. Carbohydrates and amino acids are designated as d or l according to the stereochemistry of the highest numbered carbon in the fischer projection. Nov 15, 2018 mar 08, 2020 sawhorse formula into newman projection formula stereochemistry chemistry notes edurev is made by best teachers of chemistry. Interconversion of fischer and zigzag projections learning. Finally, the steps on changing a sawhorse projection into a fischer projection will be given. Consider the carbonoxygen bond in ethanol, for example. The stereochemistry of double bonds in dietary fats fatty acid esters of glycerol is important. Such a sawhorse projection must be drawn directly from a fischer projection without any rotation. It can be a horse, table legs, armour rack and more. If we rotate this a little bit, well see the staggered conformation of ethane from a sawhorse perspective. Pdf conformational analysis is one of the significant subjects in the organic chemistry curriculum.
Now, an alternative way to depict conformations is the fronton view. So the mirror method works the best when youre working with fischer projections. This video teaches you how to quickly find configurations of molecules presented in a newman projection. 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. What are sawhorse projections in organic chemistry. Finally, lets draw the enantiomer of this compound. For pyranoses, draw the sixmembered ring laying on it side with a oxygen at the upper right.
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