Summer 2020 Chem 222-234: Take-Home Assignment 2

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Summer 2020 Chem 222-234: Take-Home Assignment 2 (100 marks)

1.   (8 marks) Provide explanations for each statement below:

a.   O-H bonds are stronger acids than N-H bonds.

b.   Primary halides are good substrates for asymmetrical ether synthesis.

c.   Diazonium salts (ArN2+) are good electrophiles in electrophilic aromatic substitutions.

d.   Hydrides from LiAlH4 reagents are strong nucleophiles and strong bases.

2.   (12 marks) Fill in the missing substrate, reagent/conditions, or product, as appropriate to complete each transformation below.

  

 

 

 

 


 

3.   (12 marks) Predict the final organic product and draw a detailed arrow-pushing mechanism for all steps in the following transformation. Pay attention to stereochemistry when needed.


 

Mechanism:

 

 


 

4.   (12 marks) Predict the final organic product and draw a detailed arrow-pushing mechanism for each step in the following transformation. Rationalize the          regiochemistry in step 2. Pay attention to stereochemistry when needed.

 

Mechanism:

 

Rationale for regiochemistry in step 2:

 


 

 

 

5.   (10 marks) Compare the two reactions below. Circle which one is faster. Draw an energy diagram (including labeled axes and annotated graph) for the first step of each                 transformation, to clearly show the differences in rates.

 


 

 

Energy Diagram Step 1 Reaction 1:

 


 

 

 

6.   (10 marks) Each of the following reaction schemes contains an error. Briefly describe the error and provide a new scheme that corrects the problem (change the over-arrow reagent or product, but not both).

 

Error, Scheme 1:

 

Corrected Scheme 1:

 

 

Error, Scheme 2:

 

Corrected Scheme 2:

 

 

 

7.    (12 marks) Develop a multi-step synthetic route to carry out the following transformation. Outline all reagents, conditions, products for each step (you may set-up as retrosynthesis if you prefer). Requires approximately 4 steps. No mechanisms needed.

 


 

 

8.    (12 marks) A student was attempting the reaction outlined below. The isolated product was analyzed by IR and 1H NMR spectroscopy. Although the IR spectrum matches well, the 1H NMR spectrum does not match the intended product. Determine the structure of the product obtained and explain why it is preferred. Assign all 1H NMR signals to specific chemical     environments or specific hydrogens in your structure, show your reasoning on the spectrum.


Reason for actual product:

 

 


 

9.   (12 marks) Using SciFinder, find a primary source (i.e. an academic journal

article) that contains a multi-step synthesis of a natural product that involves the    use of acetal protecting groups. Redraw the literature synthesis below (by hand or  using Chem Draw). Explain the need for acetal protection in the synthesis.              Provide the reference you used to obtain the synthesis, formatted using ACS style. HINT: For information on using SciFinder, refer to the “Searching the Literature” document on myCourses.

 

 

Literature synthesis:

 

Explanation for Acetal Protection:

 

Reference in ACS Style:

 


2023-03-14