Chem 51A S02 Practice Problems

Chem 51A S02 Practice Problems - 51A Practice Problems #8...

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Unformatted text preview: 51A Practice Problems #8 Winter, 2002 1. What effect would you expect on the rate of reaction of ethoxide with 1-iodobutane if the concentration of the halide were tn'pled? What if the concentration of ethoxide ion was tripled? 2. Circle the best leaving group in the following set: 0 0 II o I! 9 II o CH3CQ CH3c—69 CH3NH CH3C—NH ergo—<53 3. Rank the following substances according to 8N2 nucleophilicity towards CHSCHZCHJ a) in methanol b) in DMSO. CH3CH2CHZSee CH3CHZCHZSG CH3CH2CH209 A B Q 4. Rank the following alkyl halides in order of expected reactivity under 8N2 conditions. Write NR for any alkyl halides that would not be expected to react. CH CH3 : ,Br : ,Cl 6B: A E Q CH3 CH3 CH3 CH3 D E E 5. Show how the following two compounds, A & B, can be synthesized from the same starting material, cis-3-methylpentanol. 6. Predict the major product of the following reactions. Where important, show stereochemistry. If racemization will occur, write both enantiomers of the product. HBr ? _ H20 CH3 OH b. Tosgl A NaNa B pyrldme acetone H H O H 3CJL CH3 NaSCH3 1 equivalent m——-D' if HCN(CH3)2 (DMF) -—-—----r 51A Practice Problems #9 Winter, 2002 1. Rank the following alkyl halides in order of expected reactivity under SNl conditions. Write NR for any alkyl halides that would not be expected to react. CH CH3 : , Br : ,C1 >: , Br A E 9. CH3 CH3 CH3 CH3 D g .F. 2. Deuterium (D) is the isotope of hydrogen with mass number 2, with a proton and a neutron in its nucleus. The chemistry of deuterium is nearly identical to the chemistry of hydrogen, except that the 0-D bond is slighly stronger than the C-H bond. Reaction rates tend to be slower if a C-D bond (as opposed to a C-H bond) is broken in a rate determining step. This effect on rate is called a kinetic isotope effect. a) Propose a mechanism to explain each product in the following reaction: Br OH | KOH | —"'_"'_"—,’ CH3 + CH3CH20H Elimination product Substitution product 13) When the following deuterated compound reacts under the same conditions, the rate of formation of the substitution product is unchanged, while the rate of formation of the elimination product is slowed by a factor of seven. it 0 W K H 3CH2 7 times slower rate unchanged Explain why the elimination rate is slowed, but the substitution rate is unchanged. 3. Explain why the following compound reacts to give a mixture of alkene stereoisomers in which only the cis—dimethyl isomer contains deuterium. 4. Predict the major product of the following reactions. Where important, show stereochemistry. If racemization will occur, write both enantiomers of the product. H3 1 --“‘C NaOCHZCHa 3‘ CH3CH20H ’CH3 heat CH3 CH3 l NaCN 1). CH3_ (|:_Br 0 ll CHZCH3 F CH 9 | 3 HCEC: C. CH3W1C—BI 0 II H HCN(CH3)2 (DMF) d. _CH3 _1~I_;aN_s_, CH3CH3OH e e. H“? \ CH3OH ‘ | ' low temp ...
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This homework help was uploaded on 02/19/2008 for the course CHEM 51A taught by Professor Sangodkar during the Spring '07 term at UC Irvine.

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Chem 51A S02 Practice Problems - 51A Practice Problems #8...

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