Score: Homework Problem Set 6 Iverson CH320N Due Friday, March 10. NAME (Print): Chemistry 320N Dr. Brent Iverson 6th Homework March 3, 2017

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1 omework Problem Set 6 Iverson 320 Due Friday, March 10 AME (Print): SIGATURE: hemistry 320 Dr. Brent Iverson 6th omework March 3, 2017 Please print the first three letters of your last name in the three boxes Score: 1

2 omework Problem Set 6 Iverson 320 Due Friday, March 11 Score: 2

3 1. (8 points) Draw the two most important resonance contributing structures of the amide shown below. Be sure to show all lone pairs and formal charges. You do not have to draw arrows on this one. 2. (4 pts each) In the space provided, write the IUPA name (including stereochemistry where appropriate) for the following two molecules: (S)-5-ethyl-3-oxooctanoic acid F 3, -diethyl-5,5,5-trifluoro-3-oxopentanamide 3. (4 pts) In the space provided, draw the following molecule: (3S,4S)-3,4,5,5-tetramethylhexanamide 2 3

4 omplete the mechanism for the following acid catalyzed ester hydrolysis reaction. Be sure to show arrows to indicate movement of all electrons, write all lone pairs, all formal charges, and all the products for each step. Remember, I said all the products for each step. IF A EW IRAL ETER IS REATED I A ITERMEDIATE PRDUT, MARK IT WIT A ASTERISK AD LABEL TE PRDUT MIXTURE AS RAEMI IF RELEVAT. ext to each arrow, write which of the four mechanistic elements are indicated by the arrows you drew such as "Make a bond", "Add a proton", etc. TIE TIS!!!! At the bottom of the page, write a balanced equation that describes the overall reaction. Add a proton Take a proton away * Make a bond Racemic Add a proton Break a bond ***TIE TIS*** Product(s) Take a proton away verall Reaction: 2 S 4 (catalytic) 4

5 omplete the mechanism for the following reaction between an acid chloride and amine. Be sure to show arrows to indicate movement of all electrons, write all lone pairs, all formal charges, and all the products for each step. Remember, I said all the products for each step. IF A EW IRAL ETER IS REATED I A ITERMEDIATE PRDUT, MARK IT WIT A ASTERISK AD LABEL TE PRDUT MIXTURE AS RAEMI IF RELEVAT. ext to each arrow, write which of the four mechanistic elements are indicated by the arrows you drew such as "Make a bond", "Add a proton", etc. TIE TIS!!!! At the bottom of the page, write a balanced equation that describes the overall reaction. l Make a bond * l 3 Racemic Proton transfer l Break a bond * l 3 3 Racemic Take a proton away 3 This is an example of Mechanism B l with a proton transfer in the middle ***TIE TESE*** Products 3 verall Reaction: l l

6 omplete the mechanism for the following acid promoted amide hydrolysis reaction. Be sure to show arrows to indicate movement of all electrons, write all lone pairs, all formal charges, and all the products for each step. Remember, I said all the products for each step. IF A EW IRAL ETER IS REATED I A ITERMEDIATE PRDUT, MARK IT WIT A ASTERISK AD LABEL TE PRDUT MIXTURE AS RAEMI IF RELEVAT. ext to each arrow, write which of the four mechanistic elements are indicated by the arrows you drew such as "Make a bond", "Add a proton", etc. TIE TIS!!!! At the bottom of the page, write a balanced equation that describes the overall reaction. ormally we ignore spectator ions such as the l-, but this time we are including it in the mechanism all the way through because it helps you understand the overall process. l l From l added to 2 Add a proton Add a proton l Break a bond Take a proton away l * l Make a bond l Racemic ***TIE TIS*** l Take a proton away Products verall Reaction: l The key point is that one mole of acid is consumed for each mole of product produced. This is not catalytic in acid because the amine product is basic. or l 6 l

7 omplete the mechanism for the following base promoted ester hydrolysis reaction. o we did not make a mistake, the page is blank. We wanted to give you practice writing a mechansm without boxes or other prompts. You have to write everything. Be sure to show arrows to indicate movement of all electrons, write all lone pairs, all formal charges, and all the products for each step. Remember, I said all the products for each step. IF A EW IRAL ETER IS REATED AYWERE, MARK IT WIT A ASTERISK AD WRITE RAEMI IF RELEVAT. Make sure to write which of the four basic mechanistic elements are involved (i.e. "Make a bond", "Add a proton", etc for each reaction. Make a bond * Racemic Break a bond Take a proton away otice that we did not add acid in a second step as I did in class. All that was indicated in this question was the use of base, so the final product includes a carboxylate, not a carboxylic acid. ***TIE TIS*** This is an example of Mechanism B followed by the transfer of a proton verall Reaction: 7

8 For the following sequences of reactions, draw the predominant organic product or products after ALL the steps. You do not need to draw the intermediates formed along the way. If a new chiral center is created in the reaction that produces a racemic mixture, label the chiral center with an asterisk (*) and write "racemic" underneath. You do not have to draw all of the enantiomers. 1) Sl 2 2) 2 S 2 S 3) LiAl 4 4) 2 1) 2 r 4 2) Sl 2 3) 4) 2 MgBr 5) l, 2 (Mild acid) 8

9 Using any reagents turn the starting material into the indicated product. All carbon atoms must come from the starting material. Draw all molecules synthesized along the way. When it doubt, draw the molecule! int: this should look familiar as a homework problem. All of the carbons of the produce must come from the given starting material. (16 pts)? 1) LiAl 4 2) 2 P (Ph) 3 P PBr 3 n-buli (Ph) 3 P Br P(Ph) 3 Recognize the product as a cis alkene, the KRE of a Wittig using an alkyl Wittig reagent. Recognize further that the product has the same number of carbons as the starting ester, but that we need to make a carbon-carbon bond between a two and a three carbon piece. This can best be accomplished by reducing the ester to give two alcohols. ne alcohol is oxidized to an aldehyde with P, while the other is converted to a Wittig reagent via the alkyl halide. otice that either combination of aldehyde and Wittig regent will work just fine, I only show one combination here. 9

10 Using any reagents turn the starting material into the indicated product. All carbon atoms must come from the starting material. Draw all molecules synthesized along the way. When it doubt, draw the molecule! int: this should look familiar as a homework problem. All of the carbons of the produce must come from the given starting material. (16 pts)? 3 eat 1) l Sl 2 2) 2 + uli ui PBr 3 Br 2 Li Li Recognize the product as being a ketone, the only reaction that creates a ketone with carbon-carbon bond formation is an acid chloride plus a Gilman reagent. The required acid chloride and Gilman reaction can be derived from the ester starting material via hydrolysis, formation of an acid chloride from the acid portion, and formation of a Gilman from the alcohol portion. Alternatively, the product ketone could be made from the oxidation of the corresponding secondary alcohol, which was synthesized using a Grignard reaction. The components of the Grignard reaction could once again come from hydrolysis of the starting ester. 10