347exams_CHEM_346_Winter_2008_final_for_rework

347exams_CHEM_346_Winter_2008_final_for_rework - YOUR NAME:...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: YOUR NAME: Chemistry 346 Final Examination Winter 2008 Professor Hopkins /10 /10 /10 /10 /10 /10 /10 /1O /10 pwsgwewNH Total: /90 You are responsible for confirming that this examination contains 10 pages, including the cover sheet. This is a closed-book and closed-notes exam. Submission of this exam for grading constitutes confirmation that the work herein is your own. 1. (10 points) Draw the structure of the major organic product you predict will result from "each of the chemical reactions shown below, all of which are closely related to reactions you ran this past quarter. a NQQDL' H C (LH ———-—5 3 T 3 QHJOH [2+ 0 b. Bf L G "r \ \QHZ 2—3 CH3OH o h . c\ , , > c OH+ HONOQRX‘LO’M’Q'H‘Q d_ F NHL QNQNOL /H3P°L( OH I ' C H ——-->1 C H 0 [6 C(9ng 6 Y Q ‘9 ClaHnsol e 2. (10 points) By reference to a liquid-vapor phase diagram of your own creation, explain in some detail why the temperature vs. weight of distillate profile shown below is observed for simple and fractional distillation of a two-component mixture that exhibits ideal behavior. Figure 5—5. Comparison of a simple (A) and a fractional (B) distillation of a two-component weight of distillate ———'> I mixture. ‘ 3. (10 points) Propose a step-by-step, arrow—pushing mechanism to account for these two reactions that you performed. a. /I [UCLOH I Ce HYR “rt—3’ C6 HS /YQ6H‘ H V R oH I “4: R CGHS O C H: b Q07: H594 ‘ Cm: “HONo‘ / \ \/ é : \ 4” f¥ \ I OCH \ / \C'GHS 'H CH o/v N 3 ché Ce”: 3 3 CéHf 4. (10 points) Explain quantitatively given the Ka values (equilibrium constant for the acid dissociation in water) below why it is convenient to extract the vast majority of a carboxylic acid from an organic solvent into an aqueous solution While leaving a phenol (hydroxybenzene) in the organic layer. (You may assume that the fraction of an organic substance that is ionized corresponds to the extent that the substance Will be extracted into the aqueous layer.) K<K (H253) COLH ~ 4 (x ‘0 -4, HLQOJ \0 OH ¢\O é) '0 ‘O’H 5. (10 points) a. Given the abundance in the mass spectrum of the molecular ions below, suggest a molecular formula for this substance which contains ONLY C, H, and halogen. m/e rel. abundance 96 100 97 4.9 98 64 99 1.8 100 10 101 0.24 b. An iodo substituent (I—) has a mass of 127, as does a naphthyl subsituent (C10H7-). Explain how you could definitively distinguish without any authentic samples available to you whether a pure sample in your possession was iodomethane as opposed to l-methylnaphthalene an 3 «I i. Using low resolution mass spectrometry (in detail). 9"} f \ ii. Using high resolution mass spectrometry (explain in general). 6. (10 points) Below is the region from about 3.3 to 4.0 ppm of the 200 MHz 1H NMR spectrum of a mixture of cis- and trans-4-t—butylcyclohexanol containing the H-C-O resonance. Assign each signal to its correct stereoisomer. Draw a diagram to explain the splitting pattern for each signal, and assign the observed coupling constants to specific proton pairs. [Hintsz Remember that at 200 MHZ, one ppm equals 200 Hz. Also, under the conditions of this spectrum no coupling is observed to the hydrogen of the hydroxyl group (-OH)]. 3.523 3 502 3.480 \— 3.470 -=3=¢49—. 3.427 3 398 3 373 I I I I I I I I I I 'I" I I I 1 I I I I I I ‘1 I “1 I “I I I T I I t‘ I I 4.00 3.90 3.50 3.70 3.60 3.50 3.40 nnm rm . (10 points) In each of the below, assume you are provided a single sample of a pure compound that is one or the other of the two indicated substances. In each case name the ONE spectrometer available in the CHEM 346 lab you could use to determine which substance you have, and describe clearly how the output would distinguish between the two possible structures. (Use just one spectrometer in each of a-e, but you may use different spectrometers from one problem to the next.) You do NOT have authentic samples of these or any other compounds available to you. OH a. O HJC CHJ (j ’ 0 d O ch/rcldz B Br r 6' @gr /‘ A 8 Br gr r 8. (10 points) You are given a sample of a colorless, crystalline organic compound of unknown structure. Your goal is determine whether this substance contains an appreciable quantity of any contaminating organic materials (also of unknown structure). Name at least THREE things you could try (available in the 346 lab) to achieve this goal. In each case, describe how you would interpret the data you obtained. State at least one limitation of each method (in other words, reason the method might fail you.) 9. (10 points) Ibuprofen is an over-the-counter analgesic, available as tablets, that until recently helped me to keep pace with my 15 year old son while biking or skate skiing. The Aldrich Chemical Company sells a substance they call “(S)—(+)-4-isobutyl-oc-methylphenylacetic acid”. Ibuprofen and the substance from Aldrich provide identical proton NMR spectra in deuteriochloroform (not shown). Shown below is a portion of the 300 MHz 1H NMR spectrum of either ibuprofen (from analgesic tablets) or the substance available from Aldrich after each has been coupled to (S)- phenethylamine to yield the compound illustrated. This spectral region contains ONLY the proton resonances for the circled methyl groups. FFOm AldG‘ECL a. Explain as best you can, given the information available to you, the origin of the four lines in the top spectrum and eight lines in the bottom spectrum. b. Based upon your answer to part a, what would you predict would be the observed sign and magnitude of the optical rotation for the ibuprofen contained in an analgesic tablet? Why? l0 ...
View Full Document

This note was uploaded on 05/17/2008 for the course CHEM 347 taught by Professor Hopkins during the Spring '06 term at University of Washington.

Page1 / 10

347exams_CHEM_346_Winter_2008_final_for_rework - YOUR NAME:...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online