Name the following compounds by using the iupac system. Draw the two chair conformations for each of the following disubstituted cyclohexanes. Find the chiral centers, assign the priorities and make your assignments. Alkanes and cycloalkanes bloomsburg area school district. Conformational analysis drawing acyclic molecules newman projections conformational analysis drawing acyclic molecules sawhorse drawings which of the following is a newman projection of the following. Newman projections this is a compilation of my 5part video tutorial video series on newman projections. Draw a newman projection sighting the bond as indicated. With practice, you will see that these condensed formulas show how the atoms bond together. Below is a sawhorse projection of the gauche conformation of butane. This type of representation clearly illustrates the specific dihedral. Draw an eclipsed newman projection, with three sticks on the back carbon and three on the front. Convert the following bondline structure to the corresponding newman projection as seen from the indicated angle. It explains how to draw the newman projections of ethane, butane, and 2,3dimethylpentane. Newman projections practice problemsanswers newman.
Worksheet on newman and wedge dash projections key i would suggest doing the book problems first then attempting these. The reason for this is the fact that the absolute configuration of the chirality centers must be retained since it is the same molecule. If we want to examine the conformations about several different bonds, we must draw a different. Redrawing the product newman projection into a newman projection with the main substituents me, tbu in this case opposite to. This same picture is seen when the projection is viewed down any c c bond.
Newman projection practice 1 organic chemistry i jasperse newman projection practice a. When redrawing a fischer projection shown from a different direction, you are allowed to rotate the molecule by 180 o but not by 90 o. Everything from the basics of understanding newman projections, to energy diagrams staggered and eclipsed conformations for butane, guache, anti, and totaleclipsed interactions, to more difficult molecules, and finally, also to the conversions back into a line diagram is provided for. For each of the following, draw the best most stable and worst least stable newman projection, relative to the bond indicated in each question. These videos will help you understand everything from newman projection basics, how to convert newman to other forms, how to analyze the energy of particular conformations, and of course how to draw an energy diagram. Draw a newman projection, looking down the c 2c 3 bond, of 1butene in the conformation shown below c 2 should be your front carbon. R and s nomemclature problem 3 classify the absolute configuration of all chiral centers as r or s in the molecules below.
To verify that your answers are correct, look in your textbook at the end of chapter 4. The figure below shows fischer projection structures of 2,3dichlorobutane. Newman projections this tutorial demonstrates how to draw a newman projection. A newman projection visualizes different conformations of a carbon.
Newman projections with practice problems chemistry steps. Free software to draw newman projections stack exchange. It will likely require that you maximise your artistic skills. H this single bond fixes all of the other bonds in the newman 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. For example, for our molecule, we can look through the c1c2 bond even though it can be through any bond. The structure appears as viewed along the bond between these two atoms, and the bonds from them to other groups are drawn as projections in the plane of the paper. In a newman projection, alkyl substituent groups are subject to the most steric. Chapter 34 diastereoselectivity the felkinahn model for carbonyl conformations and diastereoselective nucleophilic attack. The ability to draw and interpret the different diagrams that are used to represent the different conformations is a very important skill to acquire. Sighting along the c2c3 bond and using newman projections. Newman projections organic chemistry tutorial video series. Chem 201beauchamp topic 6, conformations cyclohexanes 1.
How to determine the most and least stable conformations using newman projections. Newman projections alkanes, cycloalkanes, and functional. Stereoisomers a newman projection is used to represent or visualize conformations of carboncarbon bonds within a molecule. Drawing and understanding diagrams university of calgary. Draw the haworth projection so that the ring oxygen is on the top. This newman projection is in a staggered conformation, but well talk about that later. Cyclohexane chair analysis newman projections and practic. Lets get some more practice with newman projections. This organic chemistry video tutorial provides a basic introduction into newman projections.
Molecules, therefore, want to have a low strain structure. The most stable conformations will be staggered conformations with the largest groups anti to each other. If youd like to use the hexagonal template from the video in your own studies, complete and submit the form below to get it as a free pdf. Newman projection practice problems with a free book of. For this one, we will need to be able to draw newman projections as well as name the molecule using the rules of iupac nomenclature. Voiceover lets get some practice drawing newman projections. Our goal is to look down the carbon two carbon three bond for this compound, and in part a our goal is to draw the most stable conformation.
Khan academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the. Chem120 organic chemistry worksheet 1 some of the objectives. Label each drawing as staggered or eclipsed overall and indicate any gauche or antirelationships within each conformer. Newman projection is a representation of the molecule looking through a cc single bond.
Chem 201beauchamp topic 6, conformations cyclohexanes 2 how to draw a newman projection of a cyclohexane ring. Basically, what newman projections allow you to do is to visualize where are the groups on the front carbon oriented and where are the groups in the back carbon oriented and how are they related to each other. The staggered arrangement of all the bonds can be seen clearly in the newman projection. How to use newman projections to determine the most and least stable conformations of a compound. In order to draw a newman projection from a wedgedash diagram, it is useful to imagine. Draw the wedge dash projection from the newman projection and try and name the compounds from the newman projection and from the wedge dash projection. How to draw accurate newman projections tutorial first, lets define a newman projection and explain what all the parts of it mean.
What can be done with a fischer projection and what is disallowed. For each of the following, draw the best and worst newman projection, relative to the bond. R and s configuration trick for chirality of newman projections. Use hands or model atoms to help you see these configurations whenever the low priority group is facing towards you the wrong way. Newmanprojectionpractice 1 organic chemistry i jasperse newman projection practice a. Pdf conformational analysis is one of the significant subjects in the organic chemistry curriculum. You can also create the same drawing using a template.
Apr 23, 2018 this organic chemistry video tutorial provides a basic introduction into newman projections. Tips for creating a newman projection energy diagram 1. Chem 243 organic chemistry i bridgewater state university. This is especially applicable and used mostly for drawing sugars. Grab a pen and some paper, and use the model to draw newman projections for each of these from the point of view indicated by the beady little eye. Newman projections are important in organic chemistry to help you understand one aspect of molecular conformations. These two carbon atoms that form the bond are drawn as the intersection of the three black lines this is the front carbon atom and as the large black circle this is.
Manipulate the fischer projection so this hydroxyl group is on the bottom. Substituents on the right side of the fischer projection will be on the bottom face of the haworth. When looking at newman projection practice problems, there are a few areas that we need to make sure that we emphasize so you see the entire range of problems that might appear on an exam. Conformational analysis practice exercises 1 draw a newman projection of the most stable conformation of 2methylpropane. So, for this compound, were gonna look down the c three c four bond and draw the most. Introduction to newman projections organic chemistry. Draw connections over to parallel newman projection. Redrawing the product newman projection into a newman projection with the main substituents me, tbu in this case opposite to each other. Consider the following molecules written as newman projections and change them into the corresponding structure using fischer projections. I just made the ethyl groups red and the methyl group blue.
Newman projections practice problemsanswers conformational. Learn how to assign priority groups and rank substituents when the molecule is presented in newman projection without the need to redraw. We often refer to alkanes as aliphatic hydrocarbons, because the physi cal properties of the higher members of this class resemble those of the long carbonchain. By rotating the groups on the back carbon 60 degrees counterclockwise, an eclipsed newman projection can be written. Introduction to newman projections organic chemistry socratic. I would suggest doing the book problems first then attempting these. Organic chemistry i jasperse newman projection practice. Worksheet on newman and wedge dash projections key. 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. Draw the least stable conformer and calculate the total interaction energy.
Draw a newman projection, looking down the c 2 c 3 bond, of 1butene in the conformation shown below c 2 should be your front carbon. In the video we moved the front carbon, we rotated the front carbon, we held the back carbon stationary, so this ethyl group in red would move over to. The figure below shows, as an example, a newman projection looking down the c 2c 3 bond of octane. With practice, you will see that these condensed formulas show how the atoms.
Displaying all worksheets related to newman projections. Start with the antistaggered newman projection then draw and label each. Particularly 1,2dicloroethane rotamers, but have no idea if there is any program to do that kind of things. For every newman projections, you need to specify the bond and the direction from which you are looking. Newman projections more practice towson university. The newman projection is viewed on a line from the front carbon to the back carbon. I feel your pain, so i created some interactive models for you, below. For this case, we will line up the 2 and 3 carbon as labeled on the above image. Draw newman projections of the lowest and highest energy conformations of propane. To see the four steps for changing newman projections into fischer projections, click here. For each of the following, draw the best and worst newman projection, relative to the bond indicated. Chem 210 sample exam 2 20 pennsylvania state university. Chapter 4 alkanes and cycloalkanes chemconnections. For chains, draw newman projections of all conformations around a given bond and determine their energy ocsl 6.
Draw the most stable conformer and calculate the total interaction energy. Newman projection to bond line notation organic chemistry. The molecule can have no less than 2 carbon atoms, since newman projections are made by looking down a bond of carbon atoms. For pyranoses, draw the sixmembered ring laying on it side with a oxygen at the upper right. Also write one newman diagram looking down the c2c3 bond. This type of representation clearly illustrates the specific dihedral angle between the proximal and distal atoms. Worksheets are newman projections more practice answer key, cyclohexane chair analysis newman projections and practic, 331 work week 4 draw the newman projections for, newman projections p39983b, molecular modeling work answers, how to draw accurate newman projections tutorial 2, chem 210 newmann projections. Explain why the view down the c3c4 bond is more informative in identifying the best conformation. A sawhorse projection is similar to a newman projection, but it shows the carboncarbon bond that is hidden in a newman projection.
Something else thats important to note is the dihedral angle. Dec 15, 2015 r and s configuration trick for chirality of newman projections. Just as with newman projections, you can draw sawhorse projections in eclipsed and staggered conformations. Organic chemistry i jasperse cyclohexane chair practice a. How to draw newman projections and newman projection practice. Newman projections organic chemistry video clutch prep.
The front carbon atom is called proximal, while the back atom is called distal. With newman projections, youre allowed to rotate around that bond in a threedimensional way. Fischer projections with practice problems chemistry steps. Convert the following newman projections back to skeletal structures.
Are the following compounds identical or constitutional isomers. Newman projections are used to represent the relationship between two carbons in a molecule. Newman projections practice problemsanswers free download as pdf file. You can check your answers by expanding the tab below each question.
In this context, saturated means that each carbon has the maximum number of hydrogens bonded to it. Draw the newman projection the wedge and dash projection. Hopefully you can see the newman projection that we drew matches the picture from the video, and this is the same newman projection. Each of the sentences below appears verbatim in the section. Each type of structure allows a different perspective on the molecule.
828 635 147 593 166 1371 826 453 308 379 657 1107 908 1289 613 413 562 783 1165 1210 314 1226 691 1196 227 574 475 1204 1107 780 799 398 522 179 681 157 399 1207 1223 371 1412 1122