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

11/21 measurement and data processing Flashcards

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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
Q

how to calculate m/z

A

mass divided by charge

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26
Q

which part of fragmentation appears on the mass spectrometer

A

the cation

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27
Q

what is ir

A

infrared spectroscopy is a technique that can be used to help identify compounds and to determine their structure

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28
Q

what is light

A

one form of electromagnetic radiation

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29
Q

what are electromagnetic waves

A

consist of electric and magnetic fields which are perpendicular to each other and to the direction of the travel of the wave

30
Q

the electric and magnetic fields ……

A

vibrate at the same frequency as each other

31
Q

order of the em spectrum

A

radio
microwaves
infrared
visible
ultraviolet
x ray
gamma rays
rmivuxg

32
Q

what is uv light used for

A

mobement of electrons to higher energy levels

33
Q

what is infrared light used for

A

to vibrate bodns

34
Q

what is microwaves used for

A

to rotate molecules

35
Q

what is radiowave energy used for

A

to change nuclear spin

36
Q

what does nmr specrroscopy absorb

A

radio waves

37
Q

what can nmr see

A

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
Q

what can infra red spectroscopy see

A

the functional groups present

39
Q

what can uv spectroscopy see

A

conjugated systems (alterenating single and double bonds( in organic molecules as well as the metal ligand interactions in transition metal complexes)

40
Q

what can x ray crytallography see

A

how all the atoms in a molecule are connected in a 3d arrangement

41
Q

what can mass spec see

A

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
Q

types of stretching and bending vibrations

A

symmetrical, asymmetrical, bending
rocking, wagging or twisting

43
Q

what does amount of vibration depend on

A

bond strength, length and mass of each atom

44
Q

what cauess stretching and bending vibrations

A

absorption of infrared radiation

45
Q

if ir light is passed through a compound, it will…

A

absorb some of or all of the light at the frequencies at which its bonds vibrate

46
Q

wavenumebrs

A

1/wavelength

47
Q

when is ir light absorbed

A

4000-400 range

48
Q

above 1500cm is used (in ir)

A

to identify functional groups

49
Q

below 1500cm is used (in ir)

A

for fingerprinting

50
Q

a nucleus with spin…

A

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
Q

how is nmr done

A

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
Q

what solvents are used in nmr

A

ones with no H1 atoms

53
Q

signals on a 1H NMR spectrum are measured relatice to the single peak produced by

A

tetramethylsilane (TMS)

54
Q

why is tms used as the standard reference

A

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
Q

structure of tms

A

si in middle
4 methyl ch3 groups

56
Q

what does a high resolution nmr spec show

A

clusters of peaks (or signals) rather than a series of single peaks

57
Q

what is spin spin coupling

A

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
Q

how do you find the number of peaks in a particular cluster

A

look at the number of protons on the carbon atom ADJACENT to the one were interested in and add one.

59
Q

In 1H NMR, what is the term intensity is used to indicate

A

the area under the peak.

60
Q

if 0 protons on adjacent carbon atom

A

1 peak
1 rel intensity
singlet

61
Q

if 1 proton on adjacent carbon atom

A

2 peaks
1:1 rel intensity
doublet

62
Q

if 2 protons on adjacent carbon atom

A

3 peaks
1:2:1 rel intensity
triplet

63
Q

if 3 protons on adjacent carbon atom

A

4 peaks
1:3:3:1 rel intensity
quartet

64
Q

if 3 different chemical environments

A

3 different peaks

65
Q

What structural information about an organic molecule is provided by infrared spectroscopy?

A

functional groups present in the molecule

66
Q

Which of the following regions of the electromagnetic spectrum corresponds to the energy of molecular vibrations?

A

infrared

67
Q

wavelength of x rays

A

0.1nm, the same order as interatomic distances in molecules

68
Q

how does x ray diffraction work

A

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
Q

what does a diffraction pattern depend on

A

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
Q

bragg equation

A

nλ = 2d sin θ (where n is a whole number)

71
Q

what can an electron density map be used for

A

to determine the identity of atoms in a compound

72
Q

x ray diffraction identifies

A

the crystallien components

IB Chemistry HL (12 decks)

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