Formula sawhorse projection

Draw the formulae (sawhorse projection) of all the chiral conformations of 2-chloroethanol and name them. 

The first step is to convert the Fischer projection formulae into sawhorse projections. Note that for a base-induced elimination reaction of the E2 type, the tosyl group must be antiperiplanar to the proton or deutron being abstracted from the neighbouring carbon atom. As a consequence of this reaction mechanism, the configuration of the resulting double bond can be predicted. Because of the higher steric hindrance in the transition states leading to the Z isomers, in both cases the E isomer should be expected as the major product. 

The stereodescriptor erythro indicates that the chlorine atom and the hydroxy group lie on the same side of the main chain in a Fischer projection formula. Since it does not define an absolute configuration, two enantiomers must be considered. The Fischer projection formula, which represents an eclipsed conformation, is simplest first converted into a sawhorse projection (also in its eclipsed conformation) and then one side of the molecule rotated until both the reference groups, the chlorine atom and the hydroxy group, adopt an antiperiplanar arrangement. The required Newman projection formula can then be derived from these formulae. 

When we do conformational analysis, we will find that certain types of structural formulas are especially convenient to use. One of these types is called a Newman projection formula and another type is a sawhorse formula. Sawhorse formulas are much like dash-wedge three-dimensional formulas we have used so far. In conformational analyses, we will make... 

The sawhorse or Newman representations of 2-butanol, 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. Fischer projection formulas are widely used to show configurations and are quite straightforward, once one gets the idea of what they represent. 

Redraw the perspective drawings a, b, and c as Fischer projection formulas, leaving the configuration at the chiral centers unchanged. Similarly, redraw d and e in perspective, using a staggered sawhorse representation for e. 

We will rely heavily on projection formulas in this chapter as a way of representing the configurations of carbohydrates. If you are unsure of their meaning, we suggest that you review Sections 5-3C and 5-4. It is especially important to be able to translate projection formulas into models and sawhorse drawings, as shown in Figures 5-12 and 5-13. 

Draw, using dash-wedge, sawhorse, or Newman projection formulas, the important conformations of ethane, propane, butane, and various halogenated derivatives of these alkanes. 

Convert the Fischer projection formula for a tetrose to a sawhorse or Newman projection formula, and vice versa. 

If you view the second formula from the top, you will see that it is just a three-dimensional representation of the Fischer projection. Horizontal groups at each stereogenic center come up toward you, and vertical groups recede away from you. The second formula represents an eclipsed conformation of D-threose. The third and fourth formulas represent sawhorse and Newman projections, respectively, of a staggered conformation of D-threose. 

Fischer projections, 271-272, 292-293, 973-974, 977, 1007, 1056,1103 Lewis dot structures, 12 Newman projections, 90-92, 95 Structural formulas—Cent. of organic molecules, 19—21 sawhorse, 90—91 wedge-and-dash, 26, 28, 91 Structural isomers. See Constituhonal isomers Structural theory, 3... 

Learn to draw Newman projections and sawhorse formulas. Build handheld molecular models and compare them with your drawings. 

Convert the following sawhorse formula for one isomer of tartaric acid to a Fischer projection formula. Which isomer of tartaric acid is it ... 

Ammonia and amines react with epoxides with the same stereospecificity as anionic nucleophiles. Draw a sawhorse or Newman projection formula for the product of the reaction shown, clearly showing the stereochemistry at both chirality centers. What are the Cahn-lngold-Prelog R,S descriptors for these chirality centers in the reactant and the product ... 

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