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Chemistry Exam 232-003, Spring 2015: Exam Questions and Mechanisms - Prof. Kevin Shaughnes, Exams of Organic Chemistry

The study materials for an exam in chemistry 232-003, a university course, held in spring 2015 at the university of alabama. The exam covers various topics such as acidity, deuterium incorporation, nucleophilic attack, imides, enamines, reductions, hydrolysis, nitrofural synthesis, and synthetic sequences. Questions, answer keys, mechanisms, and conditions for reactions. It is a useful resource for university students preparing for exams, quizzes, and assignments related to organic chemistry.

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Chemistry 232-003, Spring 2015
Dr. Shaughnessy
Exam #2
February 23rd, 2015
Name: ANSWER KEY (print)
Honor Pledge: I promise or affirm that I will not at any time be involved with cheating,
plagiarism, fabrication, or misrepresentation while enrolled as a student at The University of
Alabama. I have read the Academic Honor Code, which explains disciplinary procedures that
will result from the aforementioned. I understand that violation of this code will result in
penalties as severe as indefinite suspension from the University.
_____________________________(signature)
You will have 1 hour and 30 minutes to complete this exam. When
time is called please stop all work and turn in your exam.
Show all work. Partial credit will be given where appropriate.
This exam has 9 pages. Make sure you have all 9 pages, and that they
are correctly copied, before starting the exam. The last page is a
periodic table
You may use molecular models to help you answer questions on this
exam.
You will not need a calculator or any other electronic device to complete
this exam.
Please put all cell phones (turn off or to silent), ipods, calculators, or
other electronic devices away in a book bag.
Your book and all notes should be placed out of sight of yourself and
your neighbors before the exam begins.
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Download Chemistry Exam 232-003, Spring 2015: Exam Questions and Mechanisms - Prof. Kevin Shaughnes and more Exams Organic Chemistry in PDF only on Docsity!

Chemistry 232- 003 , Spring 201 5

Dr. Shaughnessy

Exam # 2

February 23

rd

Name: ANSWER KEY (print)

Honor Pledge : I promise or affirm that I will not at any time be involved with cheating,

plagiarism, fabrication, or misrepresentation while enrolled as a student at The University of

Alabama. I have read the Academic Honor Code, which explains disciplinary procedures that

will result from the aforementioned. I understand that violation of this code will result in

penalties as severe as indefinite suspension from the University.

_____________________________( signature )

You will have 1 hour and 30 minutes to complete this exam. When

time is called please stop all work and turn in your exam.

Show all work. Partial credit will be given where appropriate.

This exam has 9 pages. Make sure you have all 9 pages, and that they

are correctly copied, before starting the exam. The last page is a

periodic table

You may use molecular models to help you answer questions on this

exam.

You will not need a calculator or any other electronic device to complete

this exam.

Please put all cell phones (turn off or to silent), ipods, calculators, or

other electronic devices away in a book bag.

Your book and all notes should be placed out of sight of yourself and

your neighbors before the exam begins.

Problem Score

Total (10 0 )

The exam is worth 100 points. There are 2 bonus points built in

2. For each reaction below, provide the missing starting material(s), reagent(s), or

product(s). More than one reaction step can be used in a box. For reactions in which

more than one product can be formed, draw the major product. You should not include

products formed as minor products. You do not need to indicate side products from the

reagents used. (20 points)

O

OCH

3

BrMg

excess

2. H

3

O

O

OH

O

N

O

H

N

H

, pH = 5

O

O

  1. LiAlH 4

2. H

3

O

OH

O

OH

O

a.

b.

c.

d.

e.

OH

  1. SOCl 2

HN

excess

N

  1. NaCN, H 2

O, pH=

2. H

3

O

or

  1. NaCN, H 2

O, pH=

  1. NaOH
  2. HCl

HO

OH

3. Determine whether each reaction below would work as written. If the reaction is correct as

written, write "correct" in the box. If it would not work as written, draw the product that

would actually be formed in the box. If no reaction is expected, write "no reaction." Below

each reaction that would not work, provide a set of conditions that would give the desired

product from the given starting material. You may use any necessary reagents in your

synthesis. (18 points)

O

Cl

MgBr

O

N

O

N

Br

  1. NaCN
  2. LiAlH 4

3. H

2

O

NH

2

a.

b.

c.

H

2

NNH

2

NaOH

2. H

3

O

Correct conditions

Correct conditions

Correct conditions

OH

No Reaction

or

H

2

NHN N

H

O

O

Cl

CuLi

2

O

N

O

N

  1. LiAlH 4

2. H

2

O

No Reaction

Br

NH

2

  1. Mg, ether

2. CO

2

  1. HCl
  2. SOCl 2

5. NH

3

excess

  1. LiAlH 4

7. H

2

O

5. Nitrofural is a topical antibiotic that was commonly used in ointments. It can be prepared by

the reaction of 5-nitro- 2 - furaldehyde with semicarbazide. (20 points)

a. Provide a step-by-step mechanism for this reaction showing each intermediate. Use

arrows to show the flow of electrons and indicate all formal charges.

b. Semicarbazide has three nitrogens that could potentially react with an aldehyde. Why is

N1 the most reactive?

N1 is most reactive because it is the most nucleophilic nitrogen. The lone pairs on N

and N3 are involved in resonance with the carbonyl, which means they will be less

available to act as a nucleophile.

O

O

2

N

O

H

2

N

N

H

O

NH

2

O

O

2

N

N

H

N

O

NH

2

H

pH = 5

+ H

2

O

5-nitro-2-furaldehyde semicarbazide nitrofural

O

O

2

N

O

H

2

N

N

H

O

NH

2

O

O

2

N

N

H

N

O

NH

2

O

H H

OH

2

H

2

O H

O

O

2

N

N

H

H

N

O

NH

2

OH

H OH

2

O

O

2

N

N

H

H

N

O

NH

2

OH

2

O

O

2

N

N

H

N

O

NH

2

H

OH

2

O

O

2

N

N

H

N

O

NH

2

  • H 3

O

H

2

N

N

H

O

NH

2

1

2

3

6. For each problem below, propose a synthetic sequence that would convert the given starting

materials into the product. In addition to the provided starting materials, which you can

use more than once, you may use any carbon source with ≤2 carbons. You may use any

other necessary reagent. Show the intermediate compounds that would be formed in each

step of your synthesis. Your chosen reagents should provide the desired product as the major

product in each step. (16 points)

Br

N

Br

a.

Br

  1. Mg

2. CO

2

3. H

3

O

Cl

O

Br

  1. Li
    1. CuI

CuLi

2

Cl

O

O

NH

3

, excess

NH

2

O

  1. LiAlH 4

2. H

2

O

NH

2

H

pH 5

product