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IB Chemistry HL > 11/21 measurement and data processing > Flashcards

11/21 measurement and data processing Flashcards

1
Q

what is IHD

A

index of hydrogen deficiency

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2
Q

formula for IHD

A

2

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3
Q

how do you deal with a nitrogen atom when calculating IHD

A

add one carbon atom and one hydrogen atom to the molecualr formula

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4
Q

how do you deal with an oxygen and sulfur atom when calculating IHD

A

ignore them

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5
Q

what does the IHD give

A

the number of molecuels of hydrogen needed to convert the organic compound to the corresponding saturated, non cyclic molecule.

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6
Q

how do you deal with a halogen atom when calculating IHD

A

count halogens as hydrogens (same group)

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7
Q

why must particles be ionised in a mass spectrometer

A

so they can be accelerated and deflected

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8
Q

describe the process of ionisation in a mass spectrometer

A

gaseous atoms bombarded by electrons from an electron gun and are ionised. sufficent energy is given to form ions of 1+ charge

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9
Q

describe the process of acceleration in a mass spectrometer

A

ions charged so they can be accelerated by an electric field

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10
Q

describe the process of deflection in a mass spectrometer

A

charged particels will be deflected by a magnetic or electric field

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11
Q

describe the process of detection in a mass spectrometer

A

by electric or photographic methods

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12
Q

heavier isotopes are detected…

A

less

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13
Q

what does the radius of the mass spectrometry path depend on

A

the mass/charge ratio

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14
Q

ions of heavier isotopes have larger…

A

m/z values so follow a larger radius curve.

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15
Q

most ions are… so the amount of seperation depends on their…

A

1+ charged, so depends on their mass

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16
Q

what are the steps of mass spectrometry

A

ionisation
acceleration
deflection
adetection

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17
Q

what is the y axis of a mass spectrometry

A

relative/percentage abundance

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18
Q

describe the process of fragmentation

A

a gaseous sample compound is injected into the mass spectrometer
it is bombarded by high energy electrons from an electron gun
a molecular ion is produced. contains an unpaired electron so it is also a free radical
produces a molecular ion. contains an unparied electron so is also a free radical

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19
Q

what does fragmentation produce

A

produces a molecular ion. contains an unparied electron so is also a free radical
(ion and free radical)

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20
Q

what happens if a covalent bond in the molecular ion produced by mass spectrometry

A

fragmentation

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21
Q

what parts of the of the molecular ion is attracted to the charged plates in the mass spectrometer and is detected subsequently

A

only the ion

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22
Q

what can the molecular ion also undergo

A

fragmentation or re-arrangement to produce particles of smaller mass

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23
Q

the more stable the ion,

A

the greater the intensity of the peak

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24
Q

why do some elements like bromine and chlorine have different m/z values

A

isotope

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25
how to calculate m/z
mass divided by charge
26
which part of fragmentation appears on the mass spectrometer
the cation
27
what is ir
infrared spectroscopy is a technique that can be used to help identify compounds and to determine their structure
28
what is light
one form of electromagnetic radiation
29
what are electromagnetic waves
consist of electric and magnetic fields which are perpendicular to each other and to the direction of the travel of the wave
30
the electric and magnetic fields ......
vibrate at the same frequency as each other
31
order of the em spectrum
radio microwaves infrared visible ultraviolet x ray gamma rays rmivuxg
32
what is uv light used for
mobement of electrons to higher energy levels
33
what is infrared light used for
to vibrate bodns
34
what is microwaves used for
to rotate molecules
35
what is radiowave energy used for
to change nuclear spin
36
what does nmr specrroscopy absorb
radio waves
37
what can nmr see
how neighbouring atoms of certain nuclei in a molecule are connected together, as well as how many atoms of these types are present in different locations in the molecule
38
what can infra red spectroscopy see
the functional groups present
39
what can uv spectroscopy see
conjugated systems (alterenating single and double bonds( in organic molecules as well as the metal ligand interactions in transition metal complexes)
40
what can x ray crytallography see
how all the atoms in a molecule are connected in a 3d arrangement
41
what can mass spec see
the mass to charge ration of the molecular ion (molecular weight) and the fragmentation pattern which may be related to the structure of the molecular ion
42
types of stretching and bending vibrations
symmetrical, asymmetrical, bending rocking, wagging or twisting
43
what does amount of vibration depend on
bond strength, length and mass of each atom
44
what cauess stretching and bending vibrations
absorption of infrared radiation
45
if ir light is passed through a compound, it will...
absorb some of or all of the light at the frequencies at which its bonds vibrate
46
wavenumebrs
1/wavelength
47
when is ir light absorbed
4000-400 range
48
above 1500cm is used (in ir)
to identify functional groups
49
below 1500cm is used (in ir)
for fingerprinting
50
a nucleus with spin...
generates a small magnetic field. when this is placed in a magnetic field, the fields can align with or against. the difference in alignments corresponds to the energy of radio waves.
51
how is nmr done
the sample is usually disslved in a solvent in a long thin tube and placed inside the machine where it is bombarded with radiowaves in a strong magnetic field. the stronger the better the resolution of the signals.
52
what solvents are used in nmr
ones with no H1 atoms
53
signals on a 1H NMR spectrum are measured relatice to the single peak produced by
tetramethylsilane (TMS)
54
why is tms used as the standard reference
it produces one strong peak as the twelve protons are all in the same chemical environment (this peak is then set to be at zero ppm) it is non-toxic and does not react with the compounds being investigated it absorbs radio waves in a different region (upfield) to most other protons it has a low boiling point, so it can easily be removed from the sample being analysed by evaporation.
55
structure of tms
si in middle 4 methyl ch3 groups
56
what does a high resolution nmr spec show
clusters of peaks (or signals) rather than a series of single peaks
57
what is spin spin coupling
This splitting of the peaks occurs as the effective magnetic field experienced by a particular proton is modified by the magnetic field produced by any neighbouring protons.
58
how do you find the number of peaks in a particular cluster
look at the number of protons on the carbon atom ADJACENT to the one were interested in and add one.
59
In 1H NMR, what is the term intensity is used to indicate
the area under the peak.
60
if 0 protons on adjacent carbon atom
1 peak 1 rel intensity singlet
61
if 1 proton on adjacent carbon atom
2 peaks 1:1 rel intensity doublet
62
if 2 protons on adjacent carbon atom
3 peaks 1:2:1 rel intensity triplet
63
if 3 protons on adjacent carbon atom
4 peaks 1:3:3:1 rel intensity quartet
64
if 3 different chemical environments
3 different peaks
65
What structural information about an organic molecule is provided by infrared spectroscopy?
functional groups present in the molecule
66
Which of the following regions of the electromagnetic spectrum corresponds to the energy of molecular vibrations?
infrared
67
wavelength of x rays
0.1nm, the same order as interatomic distances in molecules
68
how does x ray diffraction work
It uses a beam of monochromatic X-rays (X-rays with a single wavelength) that are directed onto a molecular crystal. The X-rays are diffracted, creating a diffraction pattern
69
what does a diffraction pattern depend on
the angle of incidence (θ), the wavelength of the incident X-rays (λ), the relative orientation of the atoms (d) and the distance between them.
70
bragg equation
nλ = 2d sin θ (where n is a whole number)
71
what can an electron density map be used for
to determine the identity of atoms in a compound
72
x ray diffraction identifies
the crystallien components

IB Chemistry HL (12 decks)

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