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Organic Chemistry Practice Exam & Answers, Exams of Organic Chemistry

Organic Chemistry Practice Exam & Answers

Typology: Exams

2021/2022

Available from 08/05/2023

tarika-arjune
tarika-arjune 🇺🇸

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CHE 224/ SPRING 2022 ANSWER KEY
EXAM 1 PART II (Chaps. 17,18) PROF. J.I. RIZZO
Answer all questions in the book provided to you in SEQUENTIAL ORDER. If
you need to skip a question, skip a page. Read each question carefully before
attempting to answer it. Only answers written in the answer book will be
considered for grading. Solutions must be legible in order for grading
consideration. The points possible for each question are indicated, for a total of 80
points for the entire examination. Good luck
1. (5 PTS) Provide the complete mechanism using Curved Arrow Formalism
for the reaction of t-butylbenzene treated with t-butylchloride in FeCl3.
Report the 1H NMR data for the major product generated. You must identify
each specific proton in your compound which corresponds to what is
reported and follow the format of chemical shift, integration, multiplicity
(e.g. Ha 1.0, 3H, triplet).
2. (5 PTS) Provide the complete mechanism using Curved Arrow Formalism
for the reaction of benzonitrile treated with the following sequence of
reactions:
1) propanoylbromide in FeBr3;
2) NH2NH2 in hydroxide (mechanism not required for this step)
Tell how many different carbons would be visualized in the 13C NMR
spectrum for the final product generated after step 2.
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CHE 224/ SPRING 2022 ANSWER KEY

EXAM 1 PART II (Chaps. 17,18) PROF. J.I. RIZZO Answer all questions in the book provided to you in SEQUENTIAL ORDER. If you need to skip a question, skip a page. Read each question carefully before attempting to answer it. Only answers written in the answer book will be considered for grading. Solutions must be legible in order for grading consideration. The points possible for each question are indicated, for a total of 80 points for the entire examination. Good luck 

  1. (5 PTS) Provide the complete mechanism using Curved Arrow Formalism for the reaction of t -butylbenzene treated with t -butylchloride in FeCl 3. Report the 1 H NMR data for the major product generated. You must identify each specific proton in your compound which corresponds to what is reported and follow the format of chemical shift, integration, multiplicity (e.g. Ha 1.0, 3H, triplet).
  2. (5 PTS) Provide the complete mechanism using Curved Arrow Formalism for the reaction of benzonitrile treated with the following sequence of reactions:
    1. propanoylbromide in FeBr 3 ;
    2. NH 2 NH 2 in hydroxide (mechanism not required for this step) Tell how many different carbons would be visualized in the 13 C NMR spectrum for the final product generated after step 2.
  1. (4 PTS) Report the 1 H and 13 C NMR data for 1,2,4-trimethyl benzene (structure shown below). You must clearly note which 1H and 13C is being reported and give the chemical shift, integration, and multiplicity (e.g. 1.0, 3H, triplet).

explain your solution by identifying corresponding pertinent signals in each spectrum. currentpoint 192837465 C O NH 2

  1. (5 PTS) Phenol and cyclohexanol have significantly different acidities. By considering their conjugate bases, deduce which compound is more acidic.

How do you expect the acidity of p -nitrophenol to compare with that of phenol? Draw each structure and explain in words and illustrate schematically your solution. The conjugate base of cyclohexanol is a simple alkoxide ion with the charge localized on oxygen. Further, the two alkyl groups attached through the carbinol carbon atom are electron donating, making the parent cyclohexanol less acidic than is methanol. However, for phenol, the negative charge of the phenoxide ion is delocalized by resonance to the ortho and para carbon sites of the ring, thereby stabilizing the anion and making the phenol a stronger acid. With a nitro group in the para position, there is even greater delocalization of negative charge away from the oxygen and stabilization of the anion, thereby making the p-nitrophenol a stronger acid than phenol.

  1. (10 PTS) Draw the major products expected with each of the following reactions: a) chlorination of p -nitrotoluene b) nitration of o -chloroaniline c) acetylation of m -dibromobenzene d) sulfonation of 2,3-dinitrotoluene e) bromobenzene treated with lithium metal in liquid ammonia, followed by workup with water SEE SOLUTIONS A THROUGH E BELOW NOTE: B) ACCEPTABLE SOLUTION IS ALSO NITRATION PARA TO AMINO GROUP.

MULTIPLE CHOICE SECTION (5 PTS EACH)

PROVIDE LETTERED ANSWERS ONLY

  1. How many 13 C signals would be observed in m -xylene? A)1 B) 2 C) 3 D) 4 E) 5 F) 6
  2. How many 13 C signals would be observed in p -nitroacetophenone? A)1 B) 2 C) 3 D) 4 E) 5 F) 6
  3. How many 13 C signals would be observed in DMAP (4-dimethylamino pyridine)? A)1 B) 2 C) 3 D) 4 E) 5 F) 6
  4. Which statement about the NMR reference compound TMS is not correct? A) TMS stands for tetramethylsilane. B) All the hydrogens in TMS have the same chemical shift. C) TMS is relatively unreactive with most functional groups. D) TMS has a high boiling point, so it is not easily lost when handling the NMR sample.
  5. Which statement is true about DEPT 135 NMR? A) only carbon atoms with a single attached hydrogen atom (methine carbon atoms) appear B) only shows carbons that have attached hydrogen atoms (quaternary carbon atoms do not appear) C) distinguishes between hydrogen atoms CH and CH3 hydrogen atoms are phased the same way (usually positive) and CH2 hydrogen atoms are phased the opposite way. D) distinguishes between carbon atoms based on their phasing. CH and CH3 carbon atoms are phased the same way (usually positive) and CH carbon atoms are phased the opposite way.