Part B: Individual Exam Questions (80 marks)

1.   (8 marks) Select the best option to fill in the blank for each of the following statements:

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

weaker

stronger

b.   Carboxylate anions (COO-) are ___________ bases than alkoxide anions (CO-).

weaker

stronger

c.   Primary halides are ___________ substrates for asymmetrical ether synthesis. poor                                                                           good

d.   Diazonium salts (ArN2+) are good ___________ in electrophilic aromatic substitutions. electrophiles                                                             nucleophiles

e.   Aldehydes are ___________ electrophiles than ketones.

worse

better

f.   Grignard reagents are ___________ nucleophiles and ___________ bases.

strong, weak

g.  NaBH4 is a ___________ reducing agent than LiAlH4 .

weaker

h.   Addition of unstabilized ylides to carbonyls yield ___________ alkenes as the major Wittig product.

Z

E

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

3.   (10 marks) Predict the final organic product and draw a detailed arrow-pushing mechanism for steps 1, 3, and 4 in the following transformation. Pay attention to stereochemistry when needed.

4.   (10 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.

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.

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).

7.    (10 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.    (10 marks) A student was attempting the reaction outlined below. The isolated product was analyzed by IR and 1H NMR spectroscopy. Although the IR 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.