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Chapter 12 practice
- Which compound would be expected to show intense IR absorption at 1746 cm
A) CH
CH
OCH
CH
B) CH
CH
CN
C) CH
CO
CH
CH
D) CH
CH
SCH
- Which of the following would not have a C-H stretch at about 3050 cm
A) 1 - pentene
B) 2 - pentene
C) 2
methyl
pentene
D) 2,3-dimethyl- 2 - pentene
E) 2,4-dimethyl- 2 - pentene
- What compound has a significant m/z 70 in its mass spectrum?
A) 1 - pentanol
B) 2 - butanol
C) diethyl ether
D) octane
E) (E)- 2 - pentene
- 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 stiffness 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
- Which of the following molecules has a characteristic stretch at 1750 cm
A) (CH
CHCH
OH
B) (CH
CH
C) (CH
CHCCCH
D) (CH
CHCH=CH
E) (CH
CHCO
CH
- The mass spectrum of which compound has M
and M+2 peaks of approximately equal intensity?
A) 3 - bromopentane
B) 3
pentanol
C) pentane
D) 3 - chloropentane
E) 3 - iodopentane
- Which compound has an IR absorption with a broad peak and a single spike at 3300 cm
A) (CH
CH
NH
B) CH
CH
CH
OH
C) CH
CH
CN
D) (CH
CH
O
E) CH
CH=CHCH
- Which compound has a strong and broad IR absorption centered at 3400 cm
A) 1 - butanol B) octane C) diethyl ether D) 2 - hexyne E) benzene
- The two most abundant isotopes of boron are
B and
B, with
B being about 4 times more abundant. In the
mass spectrum of trimethylborate [(CH 3
O)
B], ________.
A) the peaks at m/z 103 and m/z 104 have equivalent intensities
B) the peak at m/z 103 has an intensity which is 4 times that of the m/z 104 peak
C) the peak at m/z 103 has an intensity which is 1/4 the intensity of the peak at m/z 104
D) none of the above
- Which of the following does not have a broad absorption with one or more spikes that is centered about 3300
cm
in the IR?
A) (CH
CH
CH
N
B) (CH
CH
CH
NH
C) CH
CH
CH
NH
D) (CH
CNH
E) (CH
=CHCH
NH
- Which compound would be expected to show an IR absorption at 3300 cm
A) CH
CCCH
B) butane C) but- 1 - ene D) CH 3
CH
CCH
- Which compound would be expected to show intense IR absorption at 2250 cm
A) CH
CH
CH
CO
H B) (CH
CHCH
OH
C) (CH
CHCN D) CH
CH
CH
CONH
- What m/z characterizes a strong peak in the mass spectrum of cyclopentanol?
A) 86 B) 85 C) 84 D) 70 E) 68
- Absorption of what type of electromagnetic radiation results in ionization?
A) X-rays
B) radio waves
C) microwaves
D) ultraviolet light
E) infrared light
- Which of the following equations is equal to frequency?
A) hλ B) c/λ C) hc/λ D) 1/λ
- Which compound would you expect to see a broad absorption with two spikes around 3300 cm
and a strong
absorption at 1640 cm
A) CH
CH
CH
CONH
B) CH
CH
CH
CONHCH
C) CH
CH
CH
NH
D) CH
CH
CH
NHCH
- A nonlinear molecule with n atoms generally has ________ fundamental vibrational modes.
A) 2n B) 2n - 2 C) 3n D) 3n - 3 E) 3n - 6
- The energy of a photon is ________ proportional to its wavelength.
Which IR band is typically more intense, the C ≡ C stretch or the C ≡ N stretch? Explain briefly.
How does the O
- H stretch in the IR spectrum of a carboxylic acid differ from the O - H stretch of an alcohol?
- How could IR spectroscopy be used to distinguish between the following pair of compounds?
CH
COCH
CHCH
CH
and CH 3
COCH
CH
CH
CH
Answer Key
Testname: CH12PRACTICECHEM12A
1) C
2) D
3) A
4) C
5) E
6) A
7) A
8) A
9) C
10) A
11) D
12) C
13) E
14) A
15) B
16) A
17) E
- inversely
pentene
fingerprint
inversely
22) IR
- 2100 - 2200 cm
24) CO < CC < CC < OH
25) UV
- CC stretch around 1640 cm
; vinylic CH stretch above 3000 cm
27) (CH
CH
28) CH
CH
CN
- The absence of a strong, broad O-H peak (3200-3600 cm
) would indicate complete reaction of the alcohol starting
material.
The C ≡ N stretch tends to be more intense because stretching resulting in a greater change in the bond dipole.
Because of the unusually strong hydrogen bonding in carboxylic acids, the broad O-H stretch is shifted to about 3000
cm
centered on top of the usual C-H absorption. This broad O-H absorption gives a characteristic overinflated
shape to the peaks in the C-H region.
32) C
O absorption in conjugated carbonyl appears at lower wavenumber
