Stereogenic centers drawing enantiomers

Find the C bonded to four different groups in each molecule. At the stereogenic center, draw two bonds in the plane of the page, one in front (on a wedge), and one behind (on a dash). Then draw the mirror image (enantiomer). 

Butanol, for example, has one stereogenic center. To draw both enantiomers, use the typical convention for depicting a tetrahedron place two bonds in the plane, one in front of the plane... 

Problem 5.9 Locate the stereogenic center in each compound and draw both enantiomers. 

Switching the positions of H and Br (or any two groups) on one stereogenic center of either A or B forms a new stereoisomer (labeled C in this example), which is different from both A and B. Then draw the mirror image of C, labeled D. C and D are nonsuperimposable mirror images—enantiomers. We have now drawn four stereoisomers for 2,3-dibromopentane, the maximum number possible. 

To find and draw all the stereoisomers of 2,3-dibromobutane, follow the same stepwise procedure oudined in Section 5.7. Arbitrarily add the H, Br, and CH3 groups to the stereogenic centers, forming one stereoisomer A, and then draw its mirror image B. A and B are nonsuperimposable mirror images—enantiomers. 

An acid-base reaction of (R)-sec-butylamine with a racemic mixture of 2-phenylpropanoic acid forms two products having different melting points and somewhat different solubilities. Draw the structure of these two products. Assign R and S to any stereogenic centers in the products. How are the two products related Choose from enantiomers, diastereomers, constitutional isomers, or not isomers. 

How many tetrahedral stereogenic centers does PGF20 contain Draw its enantiomer. How many of its double bonds can exhibit cis-trans isomerism Considering both its double bonds and its tetrahedral stereogenic centers, how many stereoisomers are possible for PGF2a ... 

Let s return to bromochlorofluoromethane as a simple example of a chiral molecule. The two enantiomers of BrClFCH are shown as ball-and-stick models, as wedge-and-dash drawings, and as Fischer projections in Figure 7.6. Fischer projections are always generated the same way the molecule is oriented so that the vertical bonds at the stereogenic center are directed away from you and the horizontal bonds point toward you. A projection of the bonds onto the page is a cross. The stereogenic carbon Ues at the center of the cross but is not explicitly shown. 

As indicated by the asterisks, the molecule has two stereogenic centers. Each of these could have the configuration R or S. Thus, four isomers in all are possible (2R,3R), (2S,3S), (2R,3S), and (2S,3R). We can draw these four isomers as shown in Figure 5.12. Note that there are two pairs of enantiomers. The (2R,3R) and (2S,3S) forms are nonsuperimposable mirror images, and the (2R,3S) and (2S,3R) forms are another such pair. 

Chloro-2-pentene has a double bond that can have either the E or the Z configuration and a stereogenic center that can have either the R or the S configuration. How many stereoisomers are possible altogether Draw the structure of each, and group the pairs of enantiomers. 

Butanol, for example, has one stereogenic center. To draw lx)th enantiomers, use the typical convention for depicting a tetrahedron place two bonds in the plane, one in front of the plane on a wedge, and one behind the plane on a dash. Then, to form the first enantiomer A, arbitrarily place the four groups— H, OH, CH3, and CH2CH3—on any bond to the stereogenic center. 

Draw both enantiomers of mandelic acid and label each stereogenic center as R or S. 

For both amoxicillin and cephalexin (a) How many stereogenic centers does each compound contain (b) What is the maximum numb of stereoisomers possible (c) Draw the enantiomer of... 

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