wk5_lecture_1 - 10/3/2008 Which of the following structures...

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Unformatted text preview: 10/3/2008 Which of the following structures have the formula C8H14? Choose the correct formula for the following bicyclic structure: = CnH2n+2 n=9 = C9H2(9)+2 – 2(2) = C9H16 - 2(number of rings) 1 index index of hydrogen = 2 deficiency 2 3 A. = 2 and 3 D. = 2 only B. = 1 and 3 E. = all C. = 3 only F. = none A. C10H20 1 = B. C9H18 C. C10H22 D. C9H16 E. C10H18 2 Nomenclature: Choose the correct formula for the structure on the right: bridgehead constitutional isomers bicyclo 4.3.0] nonane [ 4.3.0 How does a chemical formulas change if the compound contains oxygen and/or nitrogen? O CH CH3 H H C C H H HH C H H CH CH3 C CH CH3 = C9H20 C H3C C9H20 A. bicyclo[4.3.0]nonane C. bicyclo[2.2.0]nonane B. bicyclo[4.3.0]nonane D. bicyclo[3.2.2] nonane 3 4 Hydrocarbons are rare in organic chemistry. How does this formula change when the structure contains oxygen and nitrogen? Hydrocarbons are rare in organic chemistry. How does this formula change when the structure contains oxygen and nitrogen? O CH CH3 H H C C H H HH C H H CH CH3 C CH CH3 CH CH3 H H C C H H HH C H H CH CH3 C CH CH3 = C9H20 C H3C = C9H20 C H3C C9H20 C9H20 When nitrogen is present the hydrocarbon contains one more hydrogen. OH OH O N H N H C9H20O, an ether C9H20O, an alcohol 5 C9H21N, a 2° amine H C9H21N, a 1° amine 6 1 10/3/2008 Which of the following structures have the formula C8H14O? If cholesterol has 27 carbon atoms what is its molecular formula? HO HO HO HO HO HO alkane = C27H2(27) + 2O O H alkane = C27H56O H 1 A. = 2 and 4 D. = 3 and 4 2 3 B. = 1 and 4 E. = all 4 HO H cholesterol = C27H56 - 10O cholesterol = C27H46O C. = 3 and 1 F. = none A. = C27H44O A. D. = C27H50O 7 B. = C27H40O C. = C27H46O E. = C27H48O F. C27H44OH 8 Isomerism: Isomerism: How many isomers of ethane (C2H6) exist under H H standard conditions? H C H H C H 60º H H C HH C H A = yes B = no H C HH C HH HH Are the above structures identical? isomers = compounds with the same formula but different structures. 9 (However, there are many kinds of isomers: constitutional, stereo, etc.) isomers = compounds with the same formula but different structures. 10 Which of these two structures would you predict to be more stable? What are the factors affecting conformational stability? H H H H H C H H Steric Effects H C steric effects! H C HH C A H HH H C HH B HH C H A B eclipsed staggered eclipsed staggered These two structures are two different conformations of ethane. isomers = compounds with the same formula but different structures. 11 If steric effects are important what structure would be more stable? 12 2 10/3/2008 What are the factors affecting conformational stability? C H C H What are the factors affecting conformational stability? energy Electronic Effects (bonding) torsional strain LUMO LUMO Electronic Effects (bonding) HOMO HOMO bonding MO H C H C HH MO bonding MO H C HH C H MO anti bonding A B HH HH eclipsed staggered anti bonding If electronic effects are important what structure would be more stable? 13 If electronic effects are important what structure would be more stable? 14 Can these two isomers be separated from each other? A = yes B = no How many isomers of ethane exist under standard conditions? 15 16 Can these two different structures be separated from each other under standard conditions? Can these two different structures be separated from each other under standard conditions? an energy maximum (eclipsed) torsional strain an energy minimum (staggered) energy energy an energy minimum (staggered) 12.6 kJ (3 kcal)/mol 12.6 kJ (3 kcal)/mol rotation 17 rotation 18 3 10/3/2008 What are Newman Projections? What are sawhorse Projections? H H H H H H energy H H H H H H H H H 12.6 kJ (3 kcal)/mol energy 12.6 kJ (3 kcal)/mol rotation 19 rotation 20 What are sawhorse Projections? Draw the sawhorse projection of the following Newman projection. HH H H C C H HH H C HH energy H Cl Cl H H H H Cl H C Cl H A torsional strain HH C HH HH C C H Cl Cl H C C H a partial structure C H H H C H H Cl Cl Cl H C C H B H Cl Cl Cl Cl C HH C Cl Cl H Cl Cl C HH D HH C H H C H C H 12.6 kJ (3 kcal)/mol What sawhorse projection is identical to the above Newman projection? rotation 21 22 4 ...
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