exam1 - Page 1 of 10 Chem 228 EXAM I September 21, 2010...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Page 1 of 10 Chem 228 EXAM I September 21, 2010 Name: ______KEY_____________________________________ Exam Total:_____/100pts 1. (2 pts each) Match the following IR spectra to the structures shown below. Write the letter for the matching IR spectrum on the line beneath the structure. A B C D E F Exam Version B: Spectra are rearranged, but answers are : B – C – F – D – E – A Exam I A KEY CHEM 228 – Fall 2010 12 Points Deducted: ____/____ Page 2 of 10 2. (2 pts) Give the nominal mass of the following compound. Write your answer on the line next to the structure. Version A: Version B: 3. (3 pts) Which of the following compounds has an odd nominal mass? Circle the structure to indicate your answer. The N Rule: An odd # of N gives an odd mass. 4. (3 pts) All of the compounds shown below have molecular formula C9H18. Which is most likely to give the mass spectrum reproduced here? Circle the structure to indicate your answer. 126 – 83 = 43 (C3H7), loss of propyl group Exam I A KEY CHEM 228 – Fall 2010 Points Deducted: ____/____ 8 Page 3 of 10 5. (5 pts) Calculate the molecular formula for a compound that gives the following mass spectral data. Write your answer in the space provided. Molecular formula: C7H7Cl: Partial credit (2 pts) for recognizing 1 Cl, and (2 pts) for correct # of Carbons Exam B: C3H5Br: Partial credit similar to version A. 6. (6 pts) The mass spectrum of the compound shown below shows two large fragments at m/z = 85 and m/z = 43. Give the most likely structure of each of the two fragments in the spaces provided. (Show charges!) Most likely cleavage is ‐cleavage, by the carbonyl group. ‐1 pt for cleavage on branch point on m/z = 85. 7. (2 pts) Can the compound shown below fragment by a McLafferty rearrangement? (Yes or No) Write your answer on the space provided. Answer: YES . 13 Exam I A KEY CHEM 228 – Fall 2010 Points Deducted: ____/____ Page 4 of 10 8. (3 pts each) How many signals will the following compounds show in the 1H NMR spectrum? Write your answer on the line beneath each structure. N O O 4 3 Version A: Version B: 9. (2 pts each) Identify each of the indicated sets of protons in the following compounds as unrelated (U), homotopic (H), enantiotopic (E), or diastereotopic (D). Write the letters U, H, E, or D on the line beside each structure. a. b. 10. (3 pts each) For each of the compounds shown below, give the number of signals you would see in its 13C NMR spectrum. Write your answer on the line beneath each structure. O Version A: 3 5 Version B: 11. (2 pts each) Answer the following questions about the compound shown below. f a b c d O e H Answer: __a___ (‐1 pt if “f”) a. Which atom gives the most upfield shift in a 13C NMR? b. Which atom gives the most downfield shift in a 13C NMR? Answer: __e___ c. Which atom would not give a signal in either a DEPT‐90 or a DEPT‐135 experiment? Answer: __c___ Exam I A KEY CHEM 228 – Fall 2010 Points Deducted: ____/____ Page 5 of 10 12. (3 pts each) Provide the missing portion of the following reactions. Write your answer in the space provided. Show relative stereochemistry in your answers where relevant. 22 a. b. c. 13. (3 pts each) Give the 1,2‐ and 1,4‐ addition products of the following reaction. Write your answers in the space provided. Ignore stereochemistry. Some partial credit allowances made if answer were missing a methyl group, but halogens and double bonds were in correct place. 14. (3 pts) Which of the following compounds would show the longest wavelength max in a UV spectrum? Circle the structure to indicate your answer. More conjugation = longer max More substitution = longer max Exam I A KEY CHEM 228 – Fall 2010 18 Points Deducted: ____/____ Page 6 of 10 15. Exam A (6 pts) Reproduced below are spectral data for a compound with molecular formula C5H10O. Give the structure of the compound. Partial credit given for: correct formula identifying carbonyl, more if as an aldehyde, having 2 eq methyls. Structure: O H Exam I A KEY CHEM 228 – Fall 2010 Points Deducted: ____/____ Page 7 of 10 15. Exam B (6 pts) Reproduced below are spectral data for a compound with molecular formula C6H12. Give the structure of the compound. Partial credit given for: correct formula identifying an alkene, more if as a terminal alkene, symmetrical compound. Structure: Exam I A KEY CHEM 228 – Fall 2010 6 Points Deducted: ____/____ Page 8 of 10 16. Exam A (6 pts) The spectral data for a compound with molecular formula C9H12 is shown below. Give the structure of this compound in the space at the bottom of the page. Partial credit given for: correct formula identifying an aryl ring, more if with 5H (one substituent), propyl group, more if n‐propyl Structure: Exam I A KEY CHEM 228 – Fall 2010 6 Points Deducted: ____/____ Page 9 of 10 16. Exam B (6 pts) The spectral data for a compound with molecular formula C7H14O is shown below. Give the structure of this compound in the space at the bottom of the page. Partial credit given for: correct formula identifying carbonyl, more if as a ketone, having symmetrical compound. Structure: O Exam I A KEY CHEM 228 – Fall 2010 6 Points Deducted: ____/____ Page 10 of 10 17. (3 pts) Which of the following compounds would not be a reactive diene in a Diels‐Alder reaction? Circle the structure to indicate your answer. Diene must be s‐cis and conjugated for a D‐A reaction. 18. (3 pts) Which of the following compounds would be least reactive as a dienophile in a Diels‐Alder reaction? Circle the structure to indicate your answer. Dienophile needs to be e‐ poor, conjugated to an EWG. 19. (2 pts each) Complete the following statements about the reaction shown below. Write the letter corresponding to the structure in the blank. a. The major product obtained under reversible conditions is C . Exam B: Answer is B. b. The major product obtained at low temperature is B . Exam B: Answer is C. 20. (1 pt each) Identify the analytical technique that best matches the following statements. The possible answers are: IR, 1H NMR, 13C NMR, MS and UV. Write your answer on the space beside each statement. a. This technique detects compounds that have conjugation. Answer: UV . b. The range for signals in a spectrum obtained by this technique is ~0 ‐ 200 ppm. Answer: 13C NMR . c. A technique that does not use electromagnetic radiation. Answer: MS . d. A technique that uses the highest energy electromagnetic radiation. Answer: UV . e. This technique involves promotion of electrons from the HOMO to the LUMO. Answer: UV . Bonus: Can make up for points missed on other questions, but maximum grade on exam is 100/100. (3 pts) Name two reactions or processes that we have learned about this semester that proceed through concerted mechanisms involving 6‐atom cyclic transition states. (You must get both correct to earn credit) 1. Diels‐Alder 2. Mc Lafferty fragmentation Exam I A KEY CHEM 228 – Fall 2010 15 Points Deducted: ____/____ ...
View Full Document

This note was uploaded on 02/07/2011 for the course CHEM 228 taught by Professor Tichy during the Fall '08 term at Texas A&M.

Ask a homework question - tutors are online