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Exam 1 with Answer Key for Organic Chemistry I | CHM 2211, Exams of Organic Chemistry

Material Type: Exam; Professor: Bisht; Class: Organic Chemistry II; Subject: Chemistry; University: University of South Florida; Term: Summer 2008;

Typology: Exams

Pre 2010

Uploaded on 09/29/2008

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EXAM 1 CHEMISTRY 2211 July 14th 2008
NAME (Please Print)_________________________________
TA’s Name…………….…………………………………SEC #……………….
Q. 1- 15- (2.5 points each)
1) Which compound would be expected to show intense IR absorption at 3000-3100 cm-1?
A) CH3CCCH3
B) butane
C) but-1-ene
D) CH3CH2CCH
2) Which compound would show a larger than usual M+2 peak in the mass spectrum?
A) (CH3)2CHNH2
B) CH3CHBrCH3
C) CH3CH2CO2H
D) CH3(CH2)2CH3
3) Which has a lower characteristic IR stretching frequency, the C–H or C–D bond? Explain briefly.
Answer: C–D; heavier atoms vibrate more slowly
4) What effect does conjugation typically have on the frequency at which IR absorption by C=C occurs?
A) Conjugation does not affect the frequency at which absorption occurs.
B) Conjugation increases the frequency at which absorption occurs.
C) Conjugation decreases the frequency at which absorption occurs.
5) How could IR spectroscopy be used to distinguish between the following pair of compounds?
CH2=CHCH2CH(CH3)2 and CH3COCH2CH(CH3)2
Answer: C=C stretch around 1640 cm-1; vinylic C-H stretch above 3000 cm-1 for first compound.
C=O stretch is around 1700 cm-1 and no vinylic stretch for second compound
6) The frequency of the stretching vibration of a bond in IR spectroscopy depends on what two quantities?
A) the stiffness of the bond and the electronegativity of the atoms
B) the electronegativity of the atoms and the nuclear charges of the atoms
C) the masses of the atoms and the strength of the bond
D) the nuclear charges of the atoms and the atomic radii
E) the electronegativity of the atoms and the masses of the atoms
7) Rank the following bonds in order of increasing stretching frequency (cm-1) in IR spectroscopy:
C=C, CC, C–O, and C=O.
Answer: C–O < C=C < C=O < CC
HHe
Li Be BCNOFNe
Na Mg Al Si PSCl
Ar
1a 2a 3a 4a 5a 6a 7a 0
pf3
pf4
pf5

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EXAM 1 CHEMISTRY 2211 July 14th 2008

NAME (Please Print) _________________________________

TA’s Name…………….…………………………………SEC #……………….

Q. 1- 15- (2.5 points each)

1) Which compound would be expected to show intense IR absorption at 3000-3100 cm-1? A) CH3C≡CCH

B) butane C) but-1-ene D) CH3CH2C≡CH

2) Which compound would show a larger than usual M+2 peak in the mass spectrum? A) (CH3)2CHNH

B) CH3CHBrCH

C) CH3CH2CO2H

D) CH3(CH2)2CH

3) Which has a lower characteristic IR stretching frequency, the C–H or C–D bond? Explain briefly. Answer: C–D; heavier atoms vibrate more slowly

4) What effect does conjugation typically have on the frequency at which IR absorption by C=C occurs? A) Conjugation does not affect the frequency at which absorption occurs. B) Conjugation increases the frequency at which absorption occurs. C) Conjugation decreases the frequency at which absorption occurs.

  1. How could IR spectroscopy be used to distinguish between the following pair of compounds? CH2=CHCH2CH(CH3)2 and CH3COCH2CH(CH3)

Answer: C=C stretch around 1640 cm-1; vinylic C-H stretch above 3000 cm-1 for first compound. C=O stretch is around 1700 cm-1 and no vinylic stretch for second compound

6) The frequency of the stretching vibration of a bond in IR spectroscopy depends on what two quantities? A) the stiffness of the bond and the electronegativity of the atoms B) the electronegativity of the atoms and the nuclear charges of the atoms C) the masses of the atoms and the strength of the bond D) the nuclear charges of the atoms and the atomic radii E) the electronegativity of the atoms and the masses of the atoms

7) Rank the following bonds in order of increasing stretching frequency (cm-1) in IR spectroscopy: C=C, C≡C, C–O, and C=O.

Answer: C–O < C=C < C=O < C≡C

H He

Li Be B C N O F Ne

Na Mg^ Al Si P S Cl Ar

1a 2a 3a 4a 5a 6a 7a 0

8) Which compound would be expected to show intense IR absorption at 2250 cm-1? A) CH3CH2CH2CO2H

B) (CH3)2CHCH2OH

C) (CH3)2CHCN

D) CH3CH2CH2CONH

9) Which of the following structures is consistent with the IR spectra shown below?

A) B) C) D) E)

10) The protons marked Ha and Hb in the molecule below are ____B______.

A) enantiotopic B) chemically equivalent C) diastereotopic D) none of the above

11) The protons marked Ha in the molecule below will be a __ triplet ________ (indicate the splitting here).

12) Predict the number of signals in the 13C NMR spectrum of the two cyclohexanes shown below.

__ 3 ____ signals ___7_____ signals

13) Predict the number of signals expected (disregarding splitting) in the 1H spectrum of 2-methoxybutane.

Ans: 5 signals

18. (3 points) Ultraviolet spectra were taken of the three samples with the following

results: Compound A, λ max = 208 nm (∑ = 12,000); Compound B, λ max = 302 nm

(∑ = 36,500); Compound C, λ max = 261 nm (∑ = 25,000). Which structural formula

given below belongs to Compound A, B, and C? Place your answer in the space

provided.

A C B

19. Consider the reaction below and answer the questions that follow in the spaces

provided:

i) (4 points) Write expected 1,2- and 1,4- addition products C and D.

ii) (2 points) The kinetically controlled product in the reaction is __ C _____.

20. (7.5 points) Follow the series of reactions shown below and fill in the missing

molecules and reagents.

21. (6 points) Draw mechanisms for the following reactions.