Ch3 - 58 S olutions Chpl. Chapter 2: Alkanes and...

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58 Solutions Chapter 2: Alkanes and Cycloalkanes Problem 2.65 Following is the structural formula and a ball-and-stick model of cholic acid (Chapter 26), a component of human bile whose function is to aid in the absorption and digestion of dietary fats. H ""'/ OH H Cholic acid (a) What is the conformation of ring A? of ring B? of ring C? of ring D? As can be seen in the following structures, the conformations of all of the six-membered rings, that is, A, B, and C, are all chairs. The conformation of the five-membered· ring, ring D, is puckered. These conformations all represent preferred conformations and the linkages between rings prevent chair to chair interconversion. OH(e) OH Ball-and-stickmodel of cholic acid with all but one of the Hatoms removed for clarity. (b) Are the hydroxyl groups on rings A, B, and C axial or equatorial to their respective rings? The hydroxyl group on ring A is equatorial, the hydroxyl groups on rings Band C are axial. (c) Is the methyl group at the junction of rings A and B axial or equatorial to ring A. Is it axial or equatoriai to ring B? . '. The methyl group at the A,B ring junction is equatorial to ring A, but axial to ring B. (d) Is the hydrogen at the junction of rings A and B axial or equatorial to ring A') Is it axial or equatorial to ring B? The hydrogen atom at the junction of rings A and Bis axial to ring A, but equatorial to ring B. (e) Is the methyl group at the junction of lings C and D axial or equatorial to ring C? The methyl group at the C, D junction is axial to ring C. Chpl. 3: Slereoisomerism and Chirality Solutions CHAPTER 3 Solutions to the Problems Problem 3.1 Each molecule'has one chiral center. Draw stereorepresentations for the enantiomers of each. Each part has a tetrahe'dral chiral center. The chiral centers are labeled with an asterisk. OH Q-i * C"'IH (a) 0~HJ if I / ' y: ~H(0i3h ~H{ 0i 3 h * :- Ho-C':"H H,,-C"'OH (b) Problem 3.2 Assign priorities to the groups in each set. ('~) -CH]OH and -CH2CH20H The -CM 2 0H group has higher priority because the FIRST point of difference is the underlined 0 atom of -CH2QH tbattakes priority over the underlined C atom of -CH£.H20H .. (b) -CH 2 0H and -CH=CH2 C C is treated as 11 1 2 ~'="::==-=-"----- .. ~ -C-C-H I I H H The FIRST point of difference is the underlined 0 atom of -CH&H that takes priority over any of the atoms bonded to carbon 1 of -CH=CH2. Thus, the -CH 2 0H group take'S priority over the -CH=CH 2 group. (c) -CH20H and -C(CH3h The FIRST point of difference is the underlined 0 atom of -CH&H that'takes priority overany of the carbon atoms bonded to the central carbon atom of -C(CH3h. Problem 3.3 Assign an R or S configuration 'to the chiraJ center in each molecule. The drawings underneath each molecule show the order of priority, the perspective from which to view the
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This note was uploaded on 07/09/2011 for the course CHE 301 taught by Professor Diver during the Spring '08 term at SUNY Buffalo.

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Ch3 - 58 S olutions Chpl. Chapter 2: Alkanes and...

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