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Organic Chemistry > Ch. 12 > Flashcards

Ch. 12 Flashcards

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1
Q

Absorption Spectroscopy

A

the measurement of the amount of electromagnetic radiation by a compound as a function of the wavelength

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2
Q

What are the 3 types of absorption spectroscopy

A

Infrared (IR), Nuclear magnetic resonance (NMR), ultraviolet (UV)

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3
Q

How are frequency and wavelength related?

A

Inversely

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4
Q

As energy increases, wavelenth _______, and frequency _____

A

Wavelength shortens, frequency increases

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5
Q

How does IR spectroscopy work

A

light causes molecular vibrations in the molecule

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6
Q

Wavenumber (v)

A

the number of wavelengths that fit into one centimeter that is proportional to the frequency

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7
Q

When a bond is stretched a restoring force _______; when a bond is compressed, a restoring force _______.

A

Pulls the two atoms together
Pushes the two atoms apart

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8
Q

Heavier atoms vibrate _______ than lighter atoms

A

slower

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9
Q

Stronger bonds stretch or compress better/worse than weaker bonds

A

worse

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10
Q

Stronger bonds usually vibrate ______ than weaker bonds

A

faster

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11
Q

Simple stretching vibration region(IR)

A

most common area for characteristic and predictable vibrations between 1600 and 3500

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12
Q

IR-Active

A

a vibration that changes the dipole moment of the molecule and thus can absorb infrared light

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13
Q

IR-Inactive

A

a vibration that does not change the dipole moment of the molecule and thus cannot absorb infrared light

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14
Q

A molecule that is stretched has an _____ dipole moment. A molecule that is compressed has an ______ dipole.

A

Decreased
Compressed

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15
Q

Infrared Spectrometer

A

a device that measures a compound’s absorption of infrared light as a function of frequency or wavelength

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16
Q

How long does dispersive IR take? How long does FT-IR take?

A

Dispersive takes a long time, FT-IR takes seconds

17
Q

Why doesn’t a tertiary amine show up on a spectrometer? (IR)

A

Because there is no N-H bonds

18
Q

Does resonance raise or lower carbonyl frequencies

A

lowers

19
Q

Mass spectrometry

A

method to determine the molecular mass and other valuable information about the molecular formula

20
Q

Mass spectrometer

A

An instrument that ionizes molecules, sorts the ions according to their masses and records the abundance of ions of each mass

21
Q

Electron impact ionization

A

A sample is bombarded by a beam of electrons; an electron may ionize a molecules by knbocking out an additional electron forming a radical cation

22
Q

Fragmentation

A

the breaking apart of a molecular ion upon ionization

23
Q

Only __________ fragments are detected by the mass spectrometer

A

positively charged

24
Q

How does the separation of ions of different masses occur?

A

magnetic deflection

25
Q

What is a base peak? (massspec)

A

the strongest peak in a mass spectrum

26
Q

What is a parent peak? (massspec)

A

the highest peak that is observed due to the fact that the molecule did not fragment

27
Q

What does an even number of Ns in CHN tell about the parent? An odd number? (massspec)

A

An even numb er will have an even parent, an odd number will have an odd parent
\

28
Q

High-resolution mass spectrometers can measure masses in 1 part to _______

A

20,000

29
Q

How many peaks will bromine have? What are their characteristics? (massspec)

A

two peaks, (M+, M+2)
they will have equal heights

30
Q

How many peaks will chlorine have? What are their charactersitcs? (massspec)

A

two peaks (M+ M+2)
The M+2 peak will be a third of the height of the M+ height

31
Q

What peaks will Iodine have? (massspec)

A

Iodine will have a large gap and a peak at 127

32
Q

What peak(s) will Nitrogen have? (massspec)

A

an odd number M+ peak

33
Q

How many bonds do you break to find a fragment (massspec)

A

one

34
Q

What is alpha clevage (massspec)

A

breaking the carbon-carbon bond adjacent to the carbon bearing a specified functional group; happens with ethers and amines

35
Q

What do alcohols lose during mass spectra? What peak does it create?

A

water, creates a corresponding water peak at M-18

Organic Chemistry (15 decks)

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