Which of the following statements about the ordinary IR spectroscopic regions are TRUE? - ANSWERSFalse: An IR wavelength of 40 microns corresponds to a wavenumber of 25 inverse cm
False: Ordinarily we sense most IR frequencies as colors in the region we call red.
True: We can sense some of the ...
Orgo Lab Exam 2 (Lon Capa Qs +
Lecture material) Questions & Answers
Which of the following statements about the ordinary IR spectroscopic regions are
TRUE? - ANSWERSFalse: An IR wavelength of 40 microns corresponds to a
wavenumber of 25 inverse cm
False: Ordinarily we sense most IR frequencies as colors in the region we call red.
True: We can sense some of the frequencies of the FUNDAMENTAL region of the IR
as heat.
False: In general, radio frequencies are higher wavenumbers than IR radiation.
True: In general, the IR FUNDAMENTAL region has a longer wavelength region than
the region we call the ultraviolet (uv) region.
What is the wavenumber of IR radiation designated by 21.19 microns? - ANSWERS-
one micron is 1 x 10^-6
- one cm is 1 x 10^-2
- 1/21.19 = .0471 which becomes 471 when raised to fourth power
Which of the following events may occur when IR radiation is absorbed? -
ANSWERSFalse: Bonds absorbing IR radiation do so without changing their dipole
moment.
False: Bonding electrons are promoted to higher energy molecular orbitals.
False: Chemical bonds are broken.
False: Relative nuclear spins of nucleii with non-zero Io's are changed.
True: Intra-molecular bond angles are changed.
wavelength absorption - ANSWERSAlkene: 1640 inverse cm.
Alcohol: 3300 inverse cm.
Ketones/Aldehydes: 1725 inverse cm.
Alkanes: 3000 inverse cm.
Ether: 1200 inverse cm.
Alkynes: 2200 inverse cm.
Which of the following groups MAY have no detectable IR absorption in the range
usually associated with an absorption? - ANSWERSTrue: Peroxide O-O bond.
False: Hydroxyl OH.
False: Ketene C=C=O bonds.
, True: C triple bond C.
False: Aldehyde carbonyl.
What is the SODAR of a molecule with 10 carbon atoms, 22 hydrogen atoms, and 3
oxygen atoms ? - ANSWERS- SODAR = (2C + 2 - H)/2
-0
The relative integrated signal intensities.
The number of signals.
The peak multiplicities.
The chemical shifts. - ANSWERSThe relative number of nucleii responsible for each
peak.
The number of chemically non-equivalent nucleii.
The number of adjacent, coupled nucleii.
The nature of the chemical environment for each different group of nucleii
Which of the following statements are TRUE for first-order analyses of NMR spectra -
ANSWERS- True: Equivalent protons do not split each other.
- False: The difference in absorption frequency is equal to or less than 6 J.
- True: The spin-multiplicity of the proton NMR absorption of the methylene group in
ethanol-OD is 4.
- False: First-order multiplets are symmetrical, and their chemical shift is given by the
position of the first peak in the multiplet.
- False: Carbon-13, an NMR-active nucleus, has a nuclear spin quantum number of 0.
What are the relative intensities of a NMR quintet signal? - ANSWERS1:4:6:4:1
upfield v. downfield - ANSWERS- ex: most upfield would be furthest from the carboxyl
group of an aldehyde
Which of the following statements are TRUE concerning this laboratory exercise - The
systematic identification of an organic compound ? - ANSWERSFalse: Your unknown
may be a solid, liquid, or gas.
True: Your compound , when you receive it , may be impure , ie. a component of a
mixture.
False: Your compound will contain at least C , H and oxygen and one or more of several
other possible elements such as N , one or more halogens, S and Se.
True: In a "real world" situation, the compound could be one of several million possible
known organic compounds.
True: Spectroscopic methods may be helpful in confirming the identity of your unknown.
A positive test with 2,4 dinitrophenylhydrazine could indicate the presence of which of
the following functional groups ? - ANSWERSFalse: Alcohols
False: Alkynes
True: Aldehyde or ketone
False: Amines
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