CHEM 345 Exam 1: Open-Book Instructions and Key Problems
School
Baylor University**We aren't endorsed by this school
Course
CHE 3331
Subject
Chemistry
Date
Dec 10, 2024
Pages
12
Uploaded by MateGalaxyAlligator9
1 Remember to work on scratch paper! Did you count your carbons? EXAM 1 –CHEM 345 (BULLER) February 15th, 2021 Please read these instructions carefully before beginning: 1. You will have 50 minutes to complete the exam. You will have 60 min allotted for download, digitization, troubleshooting, and uploading your completed exam. 2. You are encouraged to take a 5 min break during the exam period (50 hours is a long time to sit!), provided that you continue to follow the honor code for the exam. 3. This is an open-note and open-book exam. Model sets may be used. A periodic table, pKa table, and list of common IR and NMR data are at the end of the exam packet. 4. If you have a question while taking the exam, you may log onto Zoom and ask the instructors. Alternatively, you may send us an email. 5. Final answers must be written clearly. If you are working on the exam itself, you must write your answer in one of the supplied boxes. If you are working on blank paper, you must label the problem and put your answer inside of a box. 6. No credit will be given for illegible or ambiguous answers. 7. Exams will be submitted by scanning/photographing the relevant portions and uploading as a pdf to the appropriate Assignment in Canvas. Please write the sentence below in your own handwriting: _____________________________________________________________________________________ “I will stop after I have used my time.”I verify that the work presented on this exam is solely my own. I understand that evidence of academic misconduct may result in an irreplaceable ‘0’ for the assignment anda failing grade for the semester. Sign:____________________________________________________________________________________ (YOUR SIGNED PAGE MUST BE UPLOADED ALONG WITH PROBLEMS 1 & 2)
2 Remember to work on scratch paper! Did you count your carbons? Problem 1. (6 points, 1 point each) a) For the following compounds, clearly write the structure given the name of the compound or write the name of the compound with a given structure.
3 Remember to work on scratch paper! Did you count your carbons? Problem 2(22 points). Supply the starting materials, reaction conditions, or the product(s) needed to complete each of the following transformations. Only include products that accumulate to a significant level, but you do not need to label multiple products as major and minor. Racemic or enantiomeric products should be clearly indicated. You do not need to indicate the number of equivalents of a reagent.In some cases, no reaction may occur. Assume an aqueous workup of reactions. a. (3 points) +1/3 if meta is included. b. (4 points) +2 points for each correct bromine added. -1 for each additional bromine on top of a correct one. c. (4 points) +4 for a single oxidation. +1/4 if they have the correct oxidation and also an incorrect one.
4 Remember to work on scratch paper! Did you count your carbons? Problem 2 (cont’d). Supply the starting materials, reaction conditions, or the product(s) needed to complete each of the following transformations. Only include products that accumulate to a significant level, but you do not need to label multiple products as major and minor. Racemic or enantiomeric products should be clearly indicated. You do not need to indicate the number of equivalents of a reagent.In some cases, no reaction may occur. Assume an aqueous workup of reactions. d. (6 points) e. (6 points) Only +1/4 for (1) if the carbon source above is incorrect (so 3/6 total if the rest is correct). If direct F-C alkylation with propyl chloride, +2/6
5 Remember to work on scratch paper! Did you count your carbons? Problem 3 (17 points).Propose a reasonable multistep synthesis that would accomplish the synthesis of the following styrene from the indicated starting materials. You do not need to draw the mechanism for each step. •You must show the product of each step. •You do notneed to state the number of equivalents of a reagent for a transformation.•You are allowed to use any additional carbon source to complete the synthesis.(One fewer point is earned for a mis-drawn structure e.g. missing charge, bond, carbon, etc.) We can’t bottle charges, if you supplied a charged reactant, it must have a counterion.
6 Remember to work on scratch paper! Did you count your carbons? Problem 4. This is a 2-part problem. Read the entire problem (the next page) before beginning.Dichlorodiphenyltrichloroethane, DDT, is an effective pesticide that was banned for its adverse effect on other animals in the environment. DDT was synthesized according to the following reaction: Since then, researchers have sought to develop less-toxic analogs of DDT using alternative precursors. Your job is the draw the mechanism for the formation of one such analog. a. (12 points) The first step in the synthesis forms the benzylic alcohol drawn below. Draw a reasonable arrow-pushing mechanism for the next two stepsin the mechanism. Draw all resonance structures that contribute to the stability of resultant carbocation intermediate. If a lone pair is required to draw an arrow, then all lone pairs need to be there. (One fewer point is earned for a mis-drawn structure e.g. missing charge, bond, carbon, etc.)
7 Remember to work on scratch paper! Did you count your carbons? Problem 4 (cont’d)b. (9 points) Using the intermediate you formed in part a (redraw in the box below), complete the synthesis of the DTT analog with a reasonable arrow-pushing mechanism. You do not need to draw resonance structures to receive full credit. If answer is not boxed but correct, 2/3.
8 Remember to work on scratch paper! Did you count your carbons? Problem 5 (18 points; 3 points for each correct answer)a. In the boxes below, write the letter of the compound that will react the fastest with Cl2and FeCl3. b. In the boxes below, write the letter of the compound that will react the fastest/slowest with NaI in acetone. c. In the boxes below, write the letter of the compound that has the highest/lowest pKa.
9 Remember to work on scratch paper! Did you count your carbons? Problem 6 (15 points). The following reactions do not work as drawn. Briefly (1-2 sentences) explain what the problem is and include a molecular structure that matches your explanation. In the box provided, draw the actual product, accounting for all carbons in the starting materials. If no product forms, clearly write ‘no reaction’ in the box. Grading of the written portion was generally considered separate from the ‘no reaction’Scoring was done in tiers. +11 explanation that active electrophile will not form due to energy being too high, preventing EAS from occurring +9 Description of factors disfavoring theoretical carbocation, but no statement regarding energetics (e.g. describe carbocation, but never say that the reaction does not proceed +7 [This was an middle group that had close to 9, but too much wrong for 9] +5 minimal statement of the carbocation intermediate being too high energy/unstable (but with incorrect structures or additional info) +4 mention of carbocation having disfavorable characteristics, but implying that it forms +3 for correct explanation of carbocation rearrangement, formation of Al-O adduct, or over-alkylation (and errors in explanation of these factors resulted in lower score) +1 for recognition of FC alkylation
10 Remember to work on scratch paper! Did you count your carbons? YOU DO NOT NEED TO UPLOAD ANY OF THE REFERENCE PAGES Typical 1H-NMR Chemical Shift Ranges (in CDCl3 referenced to TMS δ = 0)Typical 13C-NMR Chemical Shift Ranges (in CDCl3 referenced to TMS δ = 0)
11 Remember to work on scratch paper! Did you count your carbons?
12 Remember to work on scratch paper! Did you count your carbons?