Spectroscopy Flashcards

0
Q

Uv spec is most useful for detecting ?

A

Conjugated alkenes

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1
Q

Mass spectroscopy results in the separation of fragments according to ?

A

Mass to charge ratio

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2
Q

How does water effect alcohols with the NMR spectra

A

The hydroxyl exchanges protons with the water , preventing it from coupling

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3
Q

The isotope c12 is not useful for NMR because ?

A

It has no magnetic moment. Only elements with an odd number of electrons can have magnetic moments

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4
Q

Chemical shifts of a proton for these functional groups in the NMR spectrum

Alkyl
Aromatic
Aldehyde
Carboxyl

A

1ppm
7ppm
9.5ppm
11ppm

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5
Q

Ir spec is most useful for distinguishing ?

A

Double and triple bonds

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6
Q

The process of measuring the frequencies of electromagnetic radiation absorbed by a molecule

A

Spectroscopy

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7
Q

IR spectroscopy measures?

A

Molecular vibrations

Stretching bonding rotation

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8
Q

The useful numbers of infrared light occur in frequency range from 400 to 4000 cm called ?

A

Wave numbers

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9
Q

Fingerprint region ?

A

Between 400 and 1500 cm which is unique to a molecule , complex vibrations

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10
Q

In order for IR light to be absorbed , the vibration of the molecule must result in ?

A

A change in the bond dipole moment

Ex o2 and br2 do not

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11
Q

Characteristic absorption frequencies ?

Single bonds
Double bonds
Triple bonds

A

1200
1600
2200

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12
Q

Functionalgroup/1700-1750/3100-3500

Alcohol
Aldehyde/ketone
Carboxylic acid
Amine

A

No Yes (broad)
Yes No
Yes. Broad peak
No. Sharp peak

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13
Q

Gives areas of absorption the appearance of valleys on the spectrum.

A

Percent transmission (the inverse of absorption) vs frequency

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14
Q

Nuclei whose magnetic moments are aligned with the field vs against the field (NMR)

A

Alpha (lower energy )

Beta (higher energy )

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15
Q

If the nuclei are exposed to electromagnetic radiation , some in lower energy of alpha will be excited into the beta state

A

Resonating

16
Q

Chemical shift is represent by the sigma symbol and with units ?

A

Parts per million (ppm)

17
Q

A peak further to the left in NMR is said to be shifted

A

Downward

18
Q

NMR is most commonly used to study ? But can also be used for ?

A

Protons /H1 nuclei and C13 nuclei

Any nucleus with an odd atomic number or odd mass number

19
Q

Proton NMR size of the peaks , the areas underneath correspond to ?

A

The number of protons producing each peak

20
Q

If a proton is next to a electron withdrawing atom , it is called ___ because ?

A

Deshielding

Pulling the electron cloud away from the nucleus moving it’s resonance to the left

21
Q

Electron donating atoms will ____ the nucleus in an H NMR spectrum . This will move it to the ?

A

Shield

Right

22
Q

TMS appears on which spectrum ?

A

NMR H1

23
Q

Peak splitting/coupling for NMR H1 ?
Number of peaks ?
Area ratios?

A

If two magnetically different protons are within 3 bonds of each other.

Number of adjacent hydrogens +1

^ number related to the triangle of numbers

24
Q

Other hydrogens influence Ha. Causes slight upfield and downfield shifts. Thus this will cause a ?

A

Dublet

25
Q

If a Ha is influenced by two nearby Hb, this causes it to have ___ different states

A

4

Alpha beta
Alpha alpha
Beta alpha
Beta beta

26
Q

Alpha beta and beta alpha have resonance frequencies occurring at ?
Alpha alpha and beta beta have frequencies ?

A

The same frequency
Different from each other and the above alpha beta /beta alpha

Results in 3 peaks instead of 4!!!

27
Q

The number of peaks that appears when splitting occurs is ?

A

N hydrogen atoms couples to give n+ 1

28
Q

For C NMR , does coupling occur between the carbon atoms ?

Where does it occur ?

A

No

Between carbon and hydrogen atoms directly attached to then

29
Q

The ability for a C NMR to record a spectrum without the coupling of adjacent protons
,

A

Spin decoupling

This just shows how the carbon atoms are affected by their adjacent functional groups

30
Q

For uv spectroscopy the higher the ___ in solution , the greater the absorbance

A

Concentration

31
Q

Uv spectrum is often used to identify ?

A

The presence or absence of a compound by measuring the absorbance at a characteristic wavelength

32
Q

The means of determining the molecular weight and structure of a molecule based on how it ionizes and decomposes under specific conditions

A

Mass spectrometry

33
Q

Mass spectrometry differs from others in 2 ways

A

No absorption of electromagnetic radiation

It’s a destructive technique

34
Q

Mass spectrometers ionize the sample with a high speed of ?

A

Electrons

35
Q

First ion formed for mass spectrometry is the ?

A

+1 cation

36
Q

Graph of mass spectrometry ?

A

Abundance(y) vs mass/charge (x)

37
Q

Tallest peak belonging to the most common ion in mass spectrometry ?

A

Base peak

This is assigned the abundance value of 100 percent

38
Q

The peak with the highest m/c ratio is almost always the ___ and from which the molecular weight can be obtained

A

Parent ion peak