Term Test 2 - Summer 2019

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University of Toronto *

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B42

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Chemistry

Date

Jan 9, 2024

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15

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CHMB42H3 TERM TEST 2 July 18 th 2019, 12:00 pm TIME ALLOWED: 90 MINUTES Exams must be written in pen for any remarking claims. Write all answers in the spaces provided. Non-programmable calculators and rulers are allowed; no other aids permitted. This exam contains 8 pages: 1 cover sheet (this page), 4 pages of questions ( double sided ), and 3 pages of charts and tables (coloured paper). The charts and tables may be removed from your test and used for rough work; they will be collected, but not be graded. Page 1___________/17 Page 2___________/12 Page 3___________/12 Page 4___________/9 Page 5___________/10 Page 6___________/5 Page 7___________/5 TOTAL___________/70
- 1 - 1) Indicate whether the following statements are TRUE or FALSE. (8 points) The M+1 peak in a mass spectrum can be used to calculate the number of carbon atoms in the compound. TRUE / FALSE The M+1 peak in a mass spectrum is approximately 1/3 the height of the molecular ion peak for compounds containing a chlorine atom. TRUE / FALSE The most useful nuclei for NMR spectroscopy are spin-active with a quantum spin number of ½ . TRUE / FALSE In the 1 H NMR of 3-methyl-1-butanol, the most upfield signal appears as a triplet. TRUE / FALSE The resonance frequency of a 13 C nucleus is influenced by both nearby nuclei and nearby electrons. TRUE / FALSE In the DEPT-135 of 4-ethylaniline, there are 3 positive signals and 1 negative signal. TRUE / FALSE Stronger bonds vibrate at higher frequencies and therefore absorb IR radiation more intensely. TRUE / FALSE Infrared radiation is absorbed when its energy matches the energy assoc LDWHG ZLWK D PROHFXOH¶V YLEUDWLRQDO PRGH± TRUE / FALSE 2) Fill in the table below for the two structures. (4 points) Number of 1 H NMR signals Number of 13 C NMR signals 3) Assign the signals to the appropriate carbon atoms in the structure below. (5 points) o.CH at N 5 i
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- 2 - 4) Assign the signals to the appropriate hydrogen atoms in the structure below. Integration has not been provided; however you should be able to answer the question without it. (8 points) 5) Fill in the missing reagents and/or structures for each of the following transformations. Where more than one product can form, show only the major product . Where the reagents are missing, more than one step may be required to complete the transformation. (16 points, 2 points per box). i i UAIHUNDIBAL 2 Hi 3 Hot Heat
- 3 -
- 4 - 6) The IR and LRMS for compound X are shown below. Use the table which follows to summarize the key structural information available from these spectra, as well as a brief rationale for each item listed. (9 points) Structural Information Rationale (Be brief! I will only read the first 10 words!)
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- 5 - 7) Compound X is a colourless liquid with the molecular formula C 7 H 14 O 2 . Its IR, 1 H NMR and 13 C NMR are provided below. Use the data provided to suggest a reasonable structure for compound X . For full marks, you must adequately annotate all spectra to support your proposed structure. (10 points) Proposed Structure:
- 6 - 8) Provide detailed stepwise mechanisms for all steps in the following reactions. a. (5 points)
- 7 - b. (5 points) For full marks, include resonance contributors for any charged intermediates. END OF TEST
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SPECTROSCOPIC CORRELATION CHARTS (can be removed from test) 1 H NMR 13 C NMR
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SPECTROSCOPIC CORRELATION CHARTS (can be removed from test) INFRARED SPECTROSCOPY
PERIODIC TABLE (can be removed from test)
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