Test 4 Review Problems Chemistry 204 Spring 2011

Extra naming rules We were a bit lenient on the quiz for the quality of names. Follow the rules in Section 18.1 of the book to help draw appropriate structures. In addition, follow these guidelines: (1) For alkenes and alkynes, a. the sp2 or sp must be included in the longest chain. If this means you have to choose a shorter chain, so be it. b. number the chain such that the multiple bond carbons have the lowest numbers possible c. For alkene rings, carbons of the multiple bond must have adjacent numbers. adf (2) The sum of the locants (numbers that indicate where substituents are) should be as small as possible. (3) If rules 1b and 2 conflict, follow rule 1b (4) List the substituents alphabetically a. “tert-“ and “sec-“ do NOT count towards alphabetizing i. ex: “tert-butyl” is alphabetized as “butyl” b. “iso-“ counts towards alphabetizing i. ex: “isobutyl” is alphebatized as “iso” (5) Hyphens separate letters from numbers, commas separate numbers

1. Name: I I

OH Cl Br F

Cl

Br

2. Draw:

4-cycloheptylpentanal

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2-benzylpropane

3-(sec-butyl)cyclobut-1-ene

3. a. Which of the following reaction coordinates would be typical for an SN1, SN2, E1, or E2 mechanism? There may be more than one answer for each reaction coordinate.

b. For a bimolecular nucleophilic substitution reaction between methylbromide and sodium hydroxide, draw the transition state and all possible products.

c. For a unimolecular elimination reaction between ethanol (weak base) and 2-iodo-2- methylbutane, draw the intermediate and all possible products.

2 4. To which mechanisms of alkyl halides (E1, E2, SN1, SN2, or neither) does each statement refer? a. Involves a carbocation intermediate. b. Its kinetics are first order in alkyl halide and first order in nucleophile. c. Its kinetics are first order in alkyl halide and zero order in nucleophile. d. Its kinetics are zero order in alkyl halide and first order in nucleophile. e. Its kinetics are first order in alkyl halide and first order in base. f. Its kinetics are first order in alkyl halide and zero order in base. g. Its kinetics are zero order in alkyl halide and first order in base. h. A good leaving group is essential. i. A pi bond is formed. O 5. Circle all that could not be products of the oxidation of ,

H O O O

Cl OR OH OH

6. Given the following kinetic data for the reaction of an alkyl bromide to its corresponding alkene in the presence of base…

[alkyl bromide] Relative

Experiment (M) [base] (M) Rate

1 0.25 0.25 2.3 2 0.25 0.5 2.3 3 0.5 0.5 4.6 4 1 1 9.2

a. What type of reaction (substitution, elimination, addition, condensation) has taken place?

b. Which of the following alkyl bromides most likely was the reactant? F F Br Br F F Br Br F

F F F F

c. Draw the structure(s) of the major product(s), including possible stereochemistry

3 7. A quaternary ammonium functional group has no acid/base character. Explain.

8. We have learned that nucleophiles are often good bases. Give two examples of when the better base is not necessarily the better nucleophile.

9. Draw all the structural isomers of the possible products when 1,3-pentadiene is reacted with the following, and name the type of reaction (both the general and specific name): a. 2 equivalents of H2

b. 1 equivalent of HCl

c. 1 equivalent of Br2

d. 2 equivalents of Br2

10. Write a likely product of the reactions listed, and name the type of reaction (there may be more than one option for each). Label any nucleophiles, electrophiles, bases, and leaving groups. a. KOH and 1-bromocyclohexane

b. NaCN and 1-iodocyclohexane

c. Tert-butoxide (bad nucleophile) and 1-bromopropane

11. For each pair of molecules, label whether they are enantiomers, diastereomers, or the same molecule.

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10) Draw a repeat unit of the polymer that results from the following monomers. Also identify the type of reaction that produces each polymer.

a) 1,6-diaminohexane: H2N(CH2)6NH2, adipic acid: HOOC(CH2)4COOH (forms Nylon-66)

b) Vinyl : CH3COOCH=CH2 (forms )

c) Tetrafluoroethene: CF2=CF2 (forms polytetrafluoroethylene, aka. Teflon)

d) Glycine (R = H) and Valine (R=CH(CH3)2), (forms a dipeptide). Here, R is the amino acid side- chain

5 11) Polyvinyl alcohol (PVA, a derivative of polyvinyl acetate) is sandwiched in between two layers of Nylon-66 for use in meat packaging. The nylon is used for its high durability and blocking properties and the PVA is used for its blocking properties.

a) Drawing two repeat units of Nylon-66 alongside each other, suggest a reason for its high durability. Also suggest a reason for its water blocking properties.

b) Why is it important to include both the Nylon and the PVA layers when packaging meat?

c) Why is it a better idea to use a simple polyethylene bag (rather than the Nylon-PVA-Nylon meat bag) when storing a fish in a bag of water at a pet store?

d) You analyze a small sample of the polyethylene fish bag in a differential scanning calorimeter (an instrument that can measure phase transitions such as ) and find a relatively broad peak centered around 117°C. Is the polyethylene likely branched or linear?

12) Consider the following questions about proteins:

a) Why can the amino acid proline discourage the formation of ά-helical structures in proteins?

b) What is the primary difference between secondary and tertiary structure?

c) Which of the following groups correctly shows the interaction that holds the secondary structure of a ß-sheet together? a. –N-H --- H-N- b. –C=O --- H-C- c. –C=O --- H-N- d. –N-H --- H-R- e. –C=O --- O=C-

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