Question 1

Infrared (IR) Spectroscopy Measures:

Accepted Answer

Absorption of infrared light which causes molecular vibration (stretching, bending, twisting, and folding)

Question 2

IR Spectra Are Generally Plotted As:

Accepted Answer

Percent transmittance vs. wavenumber (1 / λ)

Question 3

Normal Range Of An IR Spectra:

Accepted Answer

4000 to 400 cm^-1

Question 4

Fingerprint Region Of An IR Spectra:

Accepted Answer

Between 1500 and 400 cm^-1. This contains a number of peaks that can be used by experts to identify a compound.

Question 5

To Appear On An IR Spectrum, Vibration Of A Bond Must change:

Accepted Answer

The bond dipole moment.

Question 6

Certain Bonds Have Characteristic:

Accepted Answer

Absorption frequencies which allow us to infer the presence or absence of particular functional groups

Question 7

O-H Peak Is A:

Accepted Answer

Broad peak around 3300 cm^-1. Molecules with O-H include alcohols, water, and carboxylic acids.

Question 8

The Carboxylic Acid O-H Peak Will Be Around:

Accepted Answer

3000 cm^-1.

Question 9

N-H Peak Is A:

Accepted Answer

Sharp peak around 3300 cm^-1. Molecules with N-H include some amines, imines, and amides.

Question 10

C=O Peak Is A:

Accepted Answer

Sharp peak around 1750 cm^-1. Molecules with C=O include aldehydes, ketones, carboxylic acids, amides, esters, and anhydrides.

Question 11

Ultraviolet (UV) Spectroscopy Measures:

Accepted Answer

Absorption of ultraviolet light which causes movement of electrons between molecular orbitals

Question 12

UV Spectra Are Generally Plotted As:

Accepted Answer

Percent transmittance or absorbance vs. wavelength

Question 13

To Appear On A UV Spectrum, A Molecule Must Have A Small Enough Energy Difference Between Its:

Accepted Answer

Highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO) to permit an electron to move from one orbital to the other.

Question 14

The Smaller The Difference Between HOMO And LUMO:

Accepted Answer

The longer the wavelengths a molecule can absorb

Question 15

Conjugation Occurs In Molecules With:

Accepted Answer

Unhybridized p-orbitals.

Question 16

Conjugation Shifts The Absorption Spectrum To:

Accepted Answer

Higher maximum wavelengths (lower frequencies)

Question 17

Nuclear Magnetic Resonance (NMR) Spectroscopy Measures:

Accepted Answer

Alignment of nuclear spin with an applied magnetic field which depends on the magnetic environment of the nucleus itself.

Question 18

NMR Is Useful For:

Accepted Answer

Determining the structure (connectivity) of a compound, including the functional groups

Question 19

Nuclei May Be In The Lower-Energy α-State Or Higher-Energy β-State In Which:

Accepted Answer

Radiofrequency pulses push the nucleus from the α-state to the β-state and these frequencies can be measured

Question 20

Magnetic Resonance Imaging Is A:

Accepted Answer

Medical application of NMR spectroscopy

Question 21

NMR Spectra Are Generally Plotted As:

Accepted Answer

Frequency vs. absorption of energy.

Question 22

NMR Spectra Are Standardized By Using:

Accepted Answer

Chemical shift (δ), which is measured in parts per million (ppm) of spectrophotometer frequency.

Question 23

NMR Spectra Are Calibrated Using:

Accepted Answer

Tetramethylsilane (TMS) which has a chemical shift of 0 ppm

Question 24

Higher Chemical Shifts In NMR Are Located To The:

Accepted Answer

Left (downfield)

Question 25

Lower Chemical Shifts In NMR Are Located To The:

Accepted Answer

Right (upfield)

Question 26

Each Unique Group Of Protons In Proton (1H) NMR:

Accepted Answer

Has its own peak

Question 27

Integration (Area Under The Curve) Of Each Proton (1H) NMR Peak

Accepted Answer

Is proportional to the number of protons contained under the peak

Question 28

Deshielding Of Protons Occurs When:

Accepted Answer

Electron-withdrawing groups pulls electron density away from the nucleus which allows it to be more easily affected by the magnetic field.

Question 29

Deshielding Moves A Peak:

Accepted Answer

Further downfield.

Question 30

When Hydrogens Are On Adjacent Atoms, They:

Accepted Answer

Interfere with each other's magnetic environment, which causes spin-spin coupling (splitting)

Question 31

A Proton's Or Group Of Protons' Peak Is Split Into:

Accepted Answer

n+1 subpeaks, where n is the number of protons that are three bonds away from the proton of interest.

Question 32

Splitting Patterns Include:

Accepted Answer

Doublets, triplets, and multiplets

Question 33

Protons On Sp3-hybridized Carbons Are Usually In The:

Accepted Answer

0 to 3 ppm range (but higher if electron-withdrawing groups are present)

Question 34

Protons On Sp2-hybridized Carbons Are Usually In The:

Accepted Answer

4.6 to 6.0 ppm range

Question 35

Protons On Sp-hybridized Carbons Are Usually In The:

Accepted Answer

2.0 to 3.0 ppm range

Question 36

Aldehydic Hydrogens Tend To Appear:

Accepted Answer

Between 9 to 10 ppm

Question 37

Carboxylic Acid Hydrogens Tend To Appear:

Accepted Answer

Between 10.5 and 12 ppm

Question 38

Aromatic Hydrogens Tend To Appear:

Accepted Answer

Between 6.0 and 8.5 ppm

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MCAT Org. Chem Ch.11