5_all_ - 5.1 Classify each of the following objects as to...

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5.1 Classify each of the following objects as to whether it is chiral or achiral: (a) A screwdriver achiral (d) A tennis shoe chiral (g) A car chiral (b) A baseball bat achiral (e) An ear chiral (h) A hammer achiral (c ) A golf club chiral (f) A woodscrew chiral 5.2 If models are available, construct the 2-butanols represented in Fig5.3 and demonstrate for yourself that are not mutually superposable. (a) Make similar models of 2-bromopropane. Are they superposable? Solution: C CH 3 Br H CH 3 and C CH 3 H Br CH 3 (b) Is a molecule of 2-bromopropane chiral? Solution: No (c) Would you expect to find enantiomeric forms of 2-bromopropane? Solution: No 5.3 Demonstrate the validity of what we have represented in Fig. 5.5 by constructing models. Demonstrate for yourself that III and IV are related as an object and its mirror image and that they are not superposable (i.e., that III and IV are chiral molecules and are enantiomers). (a) Now take IV and exchange the positions of any two groups. What is the new relationship between the molecules? (b) Now take either models and exchange the positions of any two groups. What is the relationship between the molecules now ? X C Y W Z Mirror C X Y W Z IV III C Y W X Z V C Z Y W X VI Answer: (a) Occasionally, if you exchange the positions of X and Y, we get V. By a series of rotations, you will be able to get III which is identical with V and is the mirror image of IV.
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As a result, IV and V are chiral molecules and are enantiomers. (b) If you take IV for example, exchange the two groups such as X and Z ,you will get VI. By a series of rotations, you will get a compound which is identical with V. As a result, V are identical with VI. 5.4 Some of the molecules listed here have stereo centers; some do not. Write three-dimensional formulas for both enantiomers of those molecules that do have stereo centers. (a) 2-Fluoropropane (b) 2-Methylbutane (c) 2-Chalorobutane (d) 2-Methyl1-1-butanol (e) 2-Bromopentane (f) 3-Menthylpentane (g) 3-Methylhexane (h) 1-Chloro-2-methylbutane Answer: * Stands for stereo center (a) No stereo center (b) No stereo center (c) H 3 C C* C H 2 CH 3 H Cl CH 3 C* C H 2 H 3 C H Cl (d) C C* C H 2 CH 3 H 3 C H HO H H C C* C H 2 H 3 C CH 3 H OH H H (e) H 3 C C* C H 2 H 2 C CH 3 Br H CH 3 C* C H 2 H 2 C H 3 C Br H (f) No stereo center (g) H 3 C H 2 C C* H 2 C C H 2 CH 3 H 3 C H CH 3 H 2 C C* H 2 C C H 2 H 3 C CH 3 H (h) C C* C H 2 CH 3 H H H 3 C H Cl C C* C H 2 H 3 C H H CH 3 H Cl 5.5 Which atom is the stereocenter (a) of limonene and (b) of thalidomide? Draw bond-line formulas for the limonene and thalidomide enantiomers, showing the stereocenter in each using wedge-dashed
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wedge notation. Answer: H 3 C C CH 2 H 3 C O O O O H H 5.6 Show how a square planar structure for carbon compounds can be elimniated from consideration by considering CH 2 Cl 2 and CH 2 BrCl as examples of disubstituted methanes. (a) How many isomers would be possible in each instance if the carbon had a square planar structure? (b) How many isomers are possible in each instance if the carbon is tetrahedral? Consider CHBrClF as an example of a trisubstituted methane. (c) How many isomers would be possible if the carbon atom were square
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This note was uploaded on 02/23/2010 for the course CHEM 101 taught by Professor Smith during the Spring '10 term at Duke.

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5_all_ - 5.1 Classify each of the following objects as to...

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