CHE 331 Molecular Science II

Transcription

1 CHE 331 Molecular Science II Exam 2 Form 1 Wednesday March 9, :45 PM 10:15 PM 1. Write your nine digit University ID number in the space provided and then bubble in each of the nine digits. 2. Print your name and sign your answer form using the spaces provided. 3. Questions 1 to 10 are 5 point multiple choice questions. Bubble your answers on the answer form. Questions are short answer questions with points as indicated. Write out your answers in the indicated place on the answer form.

2 Exam CHE 331 Molecular Sciences II Page 2 of 9 1. Which of the following drawings best represents the Highest Occupied Molecular Orbital (HOMO) of the heptatrienyl anion? B 2. Choose the order that has the following compounds arranged correctly with respect to increasing acidity. (The compound with the greatest acidity should be on the right.) E 3. Which of the following compounds is not aromatic? E

3 Exam CHE 331 Molecular Sciences II Page 3 of 9 4. Six different protonation states of the amino acid tyrosine are shown below. The pk a of the carboxylic acid group is 2.2. The pk a of the protonated amine is 9.1. The pk a of the phenol is What structure best represents the predominate state of tyrosine in blood, ph = 7.3? C 5. The free energy of acid disassociation, G, for the acid shown below is kj/mol. What is the pka of the acid? B

4 Exam CHE 331 Molecular Sciences II Page 4 of 9 6. Choose the order that has the following compounds arranged correctly with respect to increasing K eq of their hydration (the compound with the greatest % of the gem diol should be on the right). B 7. Choose the answer that has the following compounds located correctly in the separation scheme. E A. toluene is in (X); the acid is in (Y); the amine is in (Z) B. toluene is in (X); the acid is in (Z); the amine is in (Y) C. toluene is in (Y); the acid is in (X); the amine is in (Z) D. toluene is in (Y); the acid is in (Z); the amine is in (X) E. toluene is in (Z); the acid is in (X); the amine is in (Y) F. toluene is in (Z); the acid is in (Y); the amine is in (X) 8. Choose the order that has the following compounds arranged correctly with respect to increasing acidity. (The compound with the greatest acidity should be on the right.) A pka values are (acetic acid 4.8, methoxyacetic acid 3.3, acetoxyacetic acid 2.8)

5 Exam CHE 331 Molecular Sciences II Page 5 of 9 9. The biycyclic acetal shown below is a synthetic framework for some potential cancer drugs. Identify its open chain form. A 10. Choose the order that has the following cations arranged correctly with respect to increasing stability. (The cation with the greatest stability should be on the right.) F

6 Exam CHE 331 Molecular Sciences II Page 6 of Calicene has a very large dipole moment (5.6 D). From an understanding of aromaticity draw an important resonance structure for calicene and indicate the negative and positive end of the dipole moment on this molecular structure. (5 pts) 12. Draw the primary product of the following reaction. (5 pts) 13. Draw the structure of protonated acetamidine. (5 pts) 14. Draw the structure of the major product of the following reaction. (5 pts)

7 Exam CHE 331 Molecular Sciences II Page 7 of When 3-buten-2-one is allowed to react with NaCN/HCN at low temperature, the expected 1,2 addition product is obtained. If the reaction temperature is raised to 80 C then a 1,4 addition product is obtained. Draw a curved arrow mechanism for the 1,4 addition clearly showing all bond making and bond breaking steps. Your chances for full credit will increase if you draw out all intermediate structures. Important Hint: Remember that primary carbocations are very unfavorable. (10 pts)

8 Exam CHE 331 Molecular Sciences II Page 8 of This is an important mechanism in sugar chemistry. Draw a curved arrow mechanism for the transformation clearly showing all bond making and bond breaking steps. Your chances for full credit will increase if you draw out all intermediate structures. (10 pts) 17. Propose a synthesis of the cyclic compound X. All your starting materials must be of four carbons or less. Hint: Start by identifying the open chain form of the hemicacetal. (10 pts)

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