CHAPTER 10: ALKENES ALKENE INTRODUCTORY TOPICS EXAMPLES. Bombykol: pheromone of silkworm. Pheromone of cabbage looper

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1 CAPTER 10: ALKENES ALKENE INTRDUCTRY TPICS EXAMPLES Bombykol: pheromone of silkworm (most of the understanding of pheromones comes from studying silkworms) Pheromone of cabbage looper (pest that eats leaves) Isoprene Common plant building block à n Structure of natural rubber Page 1

2 NMENCLATURE ALKENE NAMING 1. Number so first carbon of the C=C is the lowest # possible. Ending is ene. 2. With cyclic alkenes, the C=C is understood to be carbons #1 and #2, and doesn t need to be indicated. 3. When alkene + alcohol are in the same molecule, the name will be #-alken-#-ol. The alcohol is given the lower number. Br Page 2

3 EZ STERECEMISTRY 1) METD Divide the alkene in half, and rank the two groups on each half in terms of R/S priority rules (p + #). When the two higher ranking groups are opposite, it s the E isomer. When they are on the same side, it s the Z isomer. Naming: place the E or Z in parenthesis out in front of the name, similar to cis-trans naming. With multiple alkenes, you d include numbers like (9E, 4Z) but we won t do examples like these. 2) EXAMPLES Retinol (Vitamin A 1 ) Cl Cl Cl Page 3

4 CEMICAL SIFT IN NMR SPECTRA C- C-N C C-Cl 2 C C- C-Cl C-Br C-C ppm Page 4

5 ALKENE REACTIN VERVIEW GENERAL PATTERN Page 5

6 TERMDYNAMICS 1 Cl C C + Cl C C CANGE IN ENTALPY CANGE IN ENTRPY Predicted Sign of D S: Actual D S: CANGE IN FREE ENERGY 1 Enthalpy and entropy data from: Vollhardt, P., Schore, N., rganic Chemistry, 6 th ed., Freeman, 2011, pp. 53 Page 6

7 ALKENE REACTINS ADDITIN F X GENERAL PATTERN MECANISM 3 C C C C 3 Br ENERGY DIAGRAM Page 7

8 REGISELECTIVITY 1) DATA AND PATTERN 2 Cl Vladimir Markovnikov Stated pattern in ) EXPLANATIN 3) PRBLEM Draw two possible products for this reaction, then determine which is the major product. 2 Jones, M., Fleming, S.A., rganic Chemistry, 4 th ed., Norton, 2010, pp. 141 Page 8

9 TER FEATURES 1) STERECEMICAL CNSIDERATINS Product ratio 3 2) PRBLEMS Give the major organic product of each reaction, considering plausible rearrangements. If a significant mixture is expected (e.g. racemic mixture), show all products. Cl Br I Cl Note: rearrangement occurs on last problem 3 Jones, M., Fleming, S.A., rganic Chemistry, 4 th ed., Norton, 2010, pp. 412 Page 9

10 ADDITIN F WATER (YDRATIN) GENERAL PATTERN MECANISM ENERGY DIAGRAM STERECEMICAL CNSIDERATINS Page 10

11 BICEMICAL APPLICATIN NAD + + NAD + 8 C 2 2 C oxaloacetate SCoA SCoA 2 C C 2 C 2 citrate 2 C 2 2 C malate 2 C C 2 C 2 isocitrate 2 7 Citric Acid Cycle 3 NAD + NAD C 2 2 C C 2 2 C C 2 fumarate FAD 2 6 FAD 2 C succinate C 2 GTP + SCoA 5 GDP 2 C SCoA succinyl-scoa 4 a-ketoglutarate NAD + + SCoA NAD C 2 ADDITIN F X 2 (ALGENATIN) GENERAL PATTERN Page 11

12 MECANISM BRMINE UNSATURATIN TEST Br 2 Br 2 Compound X and Y both have a formula of C Determine a structure for each that is consistent with the following observations: bservations When a bromine solution in C 2 Cl 2 is added to a 0.05 M solution of Compound X (in C 2 Cl 2 ), the color disappears upon addition of the first 5 drops, and the orange color sustains on the 6 th drop. Possible Structure When the bromine solution is added to a 0.05 M solution of Compound Y, the color disappears upon addition of the first 10 drops, and the orange color sustains on the 11 th drop. Page 12

13 BRMINATED VEGETABLE IL Brominated vegetable oil has been used in some drinks (mostly citrusy drinks) since excess Br 2 Br Br Br Br a vegetable oil Br Br Br Br a brominated vegetable oil add Br-veg oil add Br-veg oil flavoring (oil) soda (aq) flavoring / Br-veg oil soda flavoring / Br -veg oil soda Page 13

14 ALYDRIN FRMATIN GENERAL PATTERN MECANISM EXAMPLE REGISELECTIVITY Br 2 2 Product ratio 4 Bond length of bromonium ions with differing amounts of substitution 5 4 Jones, M., Fleming, S.A., rganic Chemistry, 4 th ed., Norton, 2010, pp Solomons, G., Fryhle, C.B., rganic Chemistry, 8 th ed., Wiley, 2004, pp. 355 Page 14

15 STERESELECTIVITY Page 15

16 YDRBRATIN-XIDATIN GENERAL PATTERN MECANISM 1) YDRBRATIN STEP B 3 2) STICIMETRY B 3 Page 16

17 3) XIDATIN STEP (FYI) REGISELECTIVITY Product ratio 6 6 Solomons, G., Fryhle, C.B., rganic Chemistry, 8 th ed., Wiley, 2004, pp. 344 Page 17

18 STERESELECTIVITY WY TE REACTIN IS USEFUL 3 P 4 2 erbert Brown published rxn in 1950 s Nobel Prize in 1979 for work with boron Page 18

19 CAPTER 10 SUMMARY PRBLEMS Give the major organic product(s), paying attention to stereochemistry. Indicate if a racemic mixture is formed, or show all products if a mixture of stereoisomers is expected. Br Cl 2, C 2 Cl 2 Br 2 2 S 4 2 a. B 3 b. 2 2, Na a. Br 2, 2 b. Na Fill in the blanks to finish these sequences, showing stereochemistry if appropriate. Indicate if any products are racemic. a. C CK con. 3 P 4 b. + Page 19