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MSU
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Name: __________________ Date: 04/16/2013
PID #: __________________
Section #: _______________
TA name: _______________
QUIZ III
CEM 251 – Spring 2013 (Instructors: Prof. Robert Maleczka and Hovig Kouyoumdjian)
Total possible points = 50+5
Question 1 23pts _______
Question 2 12pts _______
Question 3 15pts _______
Bonus 5pts _______
_______________________
Total Points
Spectra obtained from: SDBSWeb: http://sdbs.riodb.aist.go.jp
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Question 1: (23 points)
Propose a structure for this compound: C7H7XO (X can be Br or Cl)
Mass Spectrograph
IR Spectrum
1H-NMR Spectrum
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1- Determine the nature of the halogen atom that you have in this compound. Explain why?
2- Now that you have a complete molecular formula, calculate the degree of unsaturation in this compound. Show your work.
3- How many carbon peaks you have in the 13C NMR spectrum. Explain why you have fewer carbon peaks in the spectrum knowing that the molecular formula has 7 carbons?
X is:
Cl
Explain briefly:
The MassSpec shows an isotopic abundance ratio of M+:M+2 = 3:1
Which is an indicative of presence of one chlorine atom?
13C-NMR Spectrum
How many carbon peaks?
Five Carbon
Peaks
Explain why you have fewer carbon peaks, knowing that the molecular formula has 7 carbons?
That is due to the presence of 5 unique carbons.
DU= [(2C+2) - H - X]/2 = 8/2 = 4
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4- a) What is the multiplicity of the peak at 3.8 ppm (1H-NMR spectrum)?
b) What is the integration of the peak at 3.8 ppm?
c) Explain why this peak occurs at 3.8 ppm.
d) Based on your answers propose a fragment from the compound.
5- Explain how you would characterize the peaks between 6.5 and 7.5 ppm (1H-NMR spectrum). Propose a fragment of the compound.
6- Using the information in all 4 spectra above, propose a structure for the unknown compound.
Draw the complete structure here:
a) Singlet
b) 3H
c) Because the proton on that carbon is bonded to an electronegative oxygen atom
d) Propose a fragment:
OCH3
Propose a fragment:
Explain briefly:
Aromatic protons occur between 6.5 – 8 ppm. The integration of these peaks is 4H, which means that this is a di-substituted benzene ring
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Question 2: (12 points)
Draw the major products or starting materials for the following reactions (Show stereochemistry if applicable).
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Question 3: (15 points)
Consider the reaction below to answer the following question(s):
1- The nucleophile in this reaction is __A__.
2- The electrophile in this reaction is __B__.
3- The kinetically controlled product in this reaction is __D___.
4- The product that results from 1,4-addition is __C___.
5- Write a stepwise mechanism that accounts for both of the products shown. Show all intermediate structures and electron flow with arrows. Circle the most stable product.
Show your work here:
Intermediate:
Intermediate:
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Bonus 4: (5 points)
The IR spectrum below is for caffeine: Which one is caffeine? Circle the molecule and explain briefly why you chose that answer below.
Explain briefly:
Other than the presence of two peaks around 1700cm-1 (which indicates that there are two carbonyls) the absence of N-H stretching peak around 3400 cm-1 excludes the presence of N-H.
There is no strong broad peak around 3500 cm-1, which excludes the possibility of presence of O-H group.
There is no peak around 2250cm-1, which excludes the possibility of presence of CN group.
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