REVIEW PROBLEMS Key. 1. Draw a complete orbital picture for the molecule shown below. Is this molecule chiral? Explain. H H.

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1 rganic hemistry II (E325) REVIEW PRBLEMS Key 1. Draw a complete orbital picture for the molecule shown below. Is this molecule chiral? Explain. 3 3 sp3 orbital p orbital sp2 orbital s orbital molecule is chiral - it has a non-superimposable mirror image 2. For each of the following compounds, draw the important resonance structures. a. ( 3 ) 2 N N 2 ( 3 ) 2 N N 2 ( 3 ) 2 N N 2 ( 3 ) 2 N N 2 b. 2 N 2 N 2 N c.

2 3. Indicate the direction of polarity for each of the bonds indicated: Mg 4. Give IUPA names for each of the following compounds: ethyl-4,6-dimethyl-2-heptyne l I (E)-2-chloro-4-iodo-2-butene (S)-2-methyl-3-isopropylcyclohexene 1-bromo-3-methylpentane N 2 o-nitrophenylbenzene l chloro-3-ethylbenzoic acid

3 5. Identify the functional groups in the following molecules. amine alkene N 2 alcohol alkene l halide (chloride) arene N 3 ether amide alkyne ester 6. Using Newman projections, show all possible conformations of 1-bromobutane. Identify the lowest and highest energy conformations lowest energy highest energy 7. Draw the two possible chair conformations of the following molecules. In each case, identify the lowest energy conformation, and explain your reasoning. compound 3 possible conformations A B A is the low energy conformation - two equatorial Me groups in A whereas in conformation B there are two axial methyl groups A B A is the low energy conformation - since the group is sterically smaller than a methyl group, the steric interaction between axial & 3 groups in A is less severe than that in B (between two axial 3 groups)

4 8. define the following terms, and give an example of each: a. nucleophile: can donate electron density to an electron deficient species examples: :N 3, PhS -, =, etc. b. electrophile: can accept electron density from an electron rich species examples: 2, R 3 -X, +, etc. 9. Show all possible stereoisomers of the following compound. Note that there are 3 stereogenic centers. Identify the relationship of each of these isomers with one another, e.g. enantiomers, diastereomers, etc. N 2 N 2 N 2 N 2 N 2 A E G N 2 N 2 N 2 N 2 B D F enantiomers: A/B, /D, E/F, G/ all other pairs are diastereomers 10. Assign the absolute configuration of each stereogenic center present in the molecule shown below. 3 S S R 2 3

5 11. Write a complete mechanism to explain the following observation: 3 l 3 l l major product minor product a l l methyl shift cation l b (path a) 3 cation (more stable) (path b) trap by chloride 3 l l minor product major product 12. Predict all products from the following reactions. Label major and minor products. l 2 K ethanol (1 equiv.) A + B NaN 2 N 3 NaN 2 D 3 2 E 1. B Lindlar Pd F G

6 l 2 Na major A + B minor D E F G 13. For each of the following transformations (A - D), the major product is shown. In each case, explain why the product formed is the major one. It may help to consider what minor products may be formed S 4 heat l 4 A B 3 3 K ethanol D 3 3 A: Protonation of the double bond in A leads to a tertiary carbocation which is then trapped by water to give the more highly substituted alcohol B (Markovnikov addition) B: Dehydration of the tertiary alcohol leads to formation of the more highly substituted double bond via an E1 elimination (Zaitsev's rule). : Anti addition of bromine across the carbon-carbon double bond (e.g. formation of a bromonium ion intermediate, followed by backside displacement to give the anti product. D: E2 elimination requires anti orientation of proton and leaving group (trans-diaxial orientation of and ). In this case, anti elimination of a proceeds so that the more hichly substituted double bond in formed. In the elimination of b, anti elimination leads to formation of the least highly subtituted double bond.

7 3 b 3 anti elimination of and a leads to more highly substituted double bond anti elimination if not possible - c is equatorial c a anti elimination of and b leads to less highly substituted double bond 14. An unknown compound had the following MS: a) identify the base peak and the parent ion in this spectrum base peak: m/z = 43 parent ion: m/z = 72 b) what is the formula weight of this compound? FW = 72

8 15. Match a structure from the list below to the following IR spectra. learly identify and label diagnostic absorbances in each IR. A B D a. ompound: D sp3 - = b. ompound: B sp2 -