Chemistry Flashcards
1
Q
Drugs
A
Substances which alter the biochemical processes within the body
2
Q
Medicines
A
Drugs with beneficial effects
3
Q
Give a brief history of drugs
A
The first drugs came from plant brews
Pharmacologically active products in plant extracts were identified
These compounds and derivatives of them were synthesised where possible
4
Q
How do medicines function
A
Most medicines work by bonding to receptors
5
Q
Receptors
A
Usually protein molecules that are on the surface of cells where they interact with small biological molecules
6
Q
Pharmacophore
A
the structural fragment of the molecule which gives it pharmacological activity
7
Q
By comparing the structure of molecules the… can be identified
A
Pharmacophore
8
Q
What can be done once the pharmacophore has been identified?
A
Chemists can design and synthesise potential medicines with a greater likelihood of success
9
Q
Why does electromagnetic radiation differ from other radiation
A
It can travel through a vacuum
10
Q
Different types of radiation have different…
A
wavelengths
11
Q
What are the highest energy radiations
A
X-rays and gamma rays
12
Q
X rays and gamma rays are packed so tightly they are less than the width of an atom, therefore they can be considered to act as….
A
Particles
13
Q
Speed of light =
A
Frequency x wave length
(C= v x n
14
Q
Wave number
A
Used for the interpretation of spectra in the ingraved region of the spectrum
The reciprocal of wavelength
15
Q
Wave number =
A
1/ wavelength = v=1\ theta
16
Q
Atoms become….when they absorb energy and their electrons move to a…
A
Excited….
Higher energy level
17
Q
Emission spectra
A
Results from exited elections moving back down to lower energy levels
18
Q
The frequency lines produced in the emissions spectrum corresponds to the….
A
Difference in energy between two energy levels
19
Q
Each line in the spectrum has a precise….that corresponds to a
A
Frequency
Value of energy (photon of energy
20
Q
Hydrogen has only one atom meaning…
A
The emissions spectra has different series of lines in different parts of the electronegativity spectrum
Depends on which level the electron falls to
21
Q
Hydrogen spectra contains one series of lines in the…
One in the…
And several in the…
A
U-V region
Visible
I-R region
22
Q
Lines in the visible spectrum correspond to electrons falling back to n=2 and are known as
A
The Balmer series
23
Q
How does a pharmacophore effect receptors
A
The shape of the pharmacophore compliments that of the receptor site, allowing it to fit into the receptor
The functional groups on pharmacophores and receptors are correctly positioned to interact and bind
24
Q
Agonists
A
Enhance the body’s natural responses (produces a response like the body’s natural compounds)
25
Antagonists
Block the body's natural responses (produces no response but prevents the body's naturally active compounds
26
Visible light
Only a small part of the electromagnetic spectrum
| A wider range would stretch from gamma rays to radio waves
27
When a beam of white light is passed through a prism (or diffraction grating) onto a white screen a .....is produced
Continuous spectrum i.e a rainbow
28
When atoms have been excited...
They emit light and other forms of energy
29
Name two ways atoms can be given extra energy
Heating a compound in a Bunsen burner or passing an electrical charge through vaporised atoms
30
If the light is viewed through a spectroscope....
The spectrum turns out to be a series of lines with different wavelengths
(And different colour colours in the Balmer series)
31
If a beam of white light radiation is passed through a gaseous sample of an element...
The radiation emerges has certain wavelengths missing. these show up as a dark line on a continuous spectrum
32
Absorption spectroscopy
Refers to spectroscopic techniques that measure the absorption of radiation as a function of frequency and wavelength due to its interaction with the sample
33
Spectra can be used to give information about....
How much of a species is present in a sample
| Eg. Lead in drinking water or a foodstuff
34
When determining the level of lead in consumables, what are the steps taken
First a calibration graph is prepared from known concentrations of lead solutions
The radiation absorbed by this sample is plotted against the concentration and when an unknown sample is analysed the concentration of lead can be found on the graph
35
Name some properties of Electromagnetic radiation
has a wavelength and frequency and can travel through a vacuum at the speed of light
36
The higher the frequency...
The shorter the wavelength
37
Photons (Quanta)
'Packets' of Electromagnetic radiation
38
Energy of a photon related to frequency is given by:
E=hv
39
Planks constant
h=6.63x10^-34 Js^-1
40
Energy of 1 mole of photons related to frequency is given by:
E=Lhv
41
Avogadro's constant (L)
6.02x10^23
42
C=
/lxv
43
Cis geometric isomers
Groups/ atoms are on the same side of the double bond
44
Trans geometric isomers
Groups/ atoms are on opposite sides of the double bond
45
Describe the changes of physical properties in geometric isomers
Geometric isomers display differences in some physical properties (melting point, boiling point)
It can also influence some chemical properties
46
Why do most geometric isomers contain a double bond
Single covalent bonds can easily rotate
47
Optical isomers
For some molecules the mirror image is a different molecule (the mirror image in non-superimposable)
Called Enantiomers
Distinguished by +/-, D/L, R/S
48
Chiral (optically active molecules)
When a molecule contains a Carbon atomic with four different groups attached
49
Racemic mixture
A 50/50 of two enantiomers
| Optically inactive
50
As energy levels get further from the nucleus, they....
Get higher in energy as they get closer together
51
When an electron reaches the merged level it has effectively been....
Removed from the atom
52
Molecules that are optical isomers are called ...
euantiomers
53
euantiomers have identical chemical and physical properties except for
Their effect on on plane polarised light
| Their interaction with other chiral molecules
54
Normal light...
Vibrates in all directions
55
Plane polarised light
Vibrates in only one direction
56
What effect do optical isomers have on polarised light
They rotate the plane
57
Quantum mechanics consider electrons as...
Waves
| Particles
58
Quantum numbers
Each electron and its energy can be defined by four quantum numbers
59
What are the 4 quantum numbers
Principle quantum number: n
Angular momentum quantum number: l
Magnetic quantum number: m*l
Spin quantum number: m*s
60
In the context of electron shells, the greater the value of n....
The greater the associated potential energy of the shell and the further it is from the nucleus
61
Subshells are defined by....
The angular momentum quantum number
62
In the context of subshells, the angular momentum quantum number..
Relates to the shape of the orbital and is given the values 0,1,2,3...ect (n-1)
63
Subshells are given the letters...
S,p,d, f
64
Electrons can be considered as acting as...
Particles and waves
65
Hersenbergs uncertainty principle
It is impossible to define with absolute certainty both the position and momentum of any electron at the same instance
66
Due to hersenbergs uncertainty principle all we can do when defining the position on an election is...
Define a region in space where the possibility of finding an electron is greater than 90%
67
Atomic orbital
The region in space where the probability of finding an electron is over 90%
68
The overall size of an orbital is governed by...
n, the principle atomic number
69
The actual shape of a orbital is given by...
The value L, the angular momentum quantum number
70
S-block
Groups 1-2
71
S orbitals
Spherical in shape
| Diameter increasesas n increases
72
To find the multiplicity and spacial orientation of p,d and f orbital it is necessary to define..
The third quantum number: Ml the magnetic quantum number
73
Ml can have any integral value between...
-L and +L
74
P block elements
Groups 3 to 0
75
P orbitals
Have two lobes ♾
76
For p orbitals l=1 so there are three possible values of ML.....
-1,0,+1
Hence there will be three degenerated orbitals (ie, orbitals with equal energies)
As they have different Ml values they have different orientations in space
77
D- orbital
L=2
| 5 possible for ML (-2,-1,0,1,2)
78
For d- orbitals when n is greater than or equal to 3 there are...
5 degenerated orbitals
79
F-orbitals
L=3
| 7 possible values for ML(-3,-2,-1,0,+1,+2,+3)
80
To completely identify an individual electron a fourth quantum number is required called
Spin quantum number, Ms
81
No two electrons and anyone atom can have the same...
Set of four quantum numbers
82
Due to no two electrons in any atom having the same set of four quantum numbers what are some important assumptions we make?
The maximum number of electrons in any orbital is two
| If there are any two electrons in the same orbitally must have opposite spins
83
What are the two values a spin quantum number can have
+1/2
| -1/2
84
Mass spectrometry
Used to determine the accurate molecular mass and structural features of an organic compound
85
In mass spectrometry, the peak with the highest M/Z ratio provides
the gram formula mass of the organic compound
86
Base peak (mass spectrometry)
The most abundant peak (the tallest)
87
Hund’s rule of Maximum Multiplicity
When electrons occupy degenerated orbitals the electrons fill each orbital singularly, keeping their spins parallel before spin pairing occurs
88
The AUFBAU principle
Orbitals of lowest energy levels are always filled first
89
The structure of the periodic table depends on...
The electron configuration of elements
90
IR Spectroscopy use
Used to identify specific functional groups in organic compounds
91
Describe how IR spectroscopy works
IR radiation is made up of a continuous range of frequencies. by shining these at organic compounds, sone are absorbed and some are not
Those absorbed cause parts of molecules to vibrate
The wavelengths which are absorbed depend on a type of chemical bond and groups or atoms at the end of these bonds
92
Types of Bond Vibration
Bond bending
| Bond stretching
93
Bond stretching
Energy of the bond vibration depends on bond length, mass of atoms ect.
Therefore different bonds vibrate in different ways with different energies.
By shining IR radiation with exactly the right frequencies, you can kick the bond into a high state of energies
94
Bond bending
Same principle applies as bond stretching but the frequency of the absorbed radiation differs
95
Electron density
The attraction between the nuclei and electrons causes electron density to occur between the two nuclei (molecular orbital)
96
We use different electronegatives to gauge....
The polarity of bonds between atoms
97
In F2 the difference in electronegativities is 0 hence
It is non polar
98
In HF the difference in electronegativities is 1.8 hence
Polar
99
In liF the difference in electronegativities is 3 hence
Ionic (very polar)
100
Bonded pairs
Electron pairs shared between two atoms
101
Lone/ non-bonded pairs
An electron pair that remains on the atom are not shared
102
Nuclear magnetic Resonance (NMR) Spectrometry
User to gain information about the chemical environment of hydrogen atoms in organic molecules
103
Describe the theory behind NMR
Hydrogen nuclei spin on their own axises, either clockwise or anti clockwise.
Absorption or radiation in the radio frequency region causes the low energy nuclei to flip to the higher energy orientation
The radiation emitted when the nuclei relax back to the low energy orientation is defected and plotted as a spectrum of lines
104
Tetramethylsilane (TMS)
```
The lines on a spectrum are positioned relative to a standard substance, this is typically TMS
The line (peak) produced by the 12 H atoms in TMS is set at zero
```
105
Chemical shift
The position of other H atoms away from the TMS peak
106
What 3 pieces of information can be gained from a spectrum
The number of different hydrogen environments
The number of hydrogen atoms in an environment
The number of hydrogen atoms on adjacent carbon atoms
107
How does an NMR graph show the number of different hydrogen environments
Each hydrogen environment produces a peak at a different chemical shift
A chart of environments and chemical shifts is shown on pg16 on data booklet
108
How does an NMR graph show the number of hydrogen atoms environments in each environment
The area under the peak of each environment gives the ratio of the number of hydrogen atoms present
109
N+1 rule for NMR
```
N= no of hydrogen
N+1= number of adjacent h atoms
```
110
How to write lewis dot diagrams
Calculate the total number of valency electrons
| Find the central atom and number of bonds
111
If there are two things around a central atom it could be a...
Linear molecule
112
If there are three things around a central atom it could be a...
Trigonal planar
| Bent
113
If there are four things around a central atom it could be a...
Tetrahedral
| Trigonal pyramidal
114
If there are six things around a central atom it could be a...
Octahedral
Square pyramidal
Square planar
115
The angle on a linear molecule is....
180°
116
The angle on a trigonal planar is....
120°
117
The angle on a bent molecule is....
116°
| Or 105° if 4 things around central atom
118
The angle on a tetrahedral molecule is....
109.5°
119
The angle on a trigonal pyramidal molecule is....
107
120
The angle on a octehedral molecule is....
90°
121
The angle on a square pyramidal molecule is....
90°
122
The angle on a square planar molecule is....
90°
123
The shape of methane is...
Tetrahedral
124
The shape of Ammonia is...
Trigonal pyramidal
125
The shape of water is....
Bent
126
What are some trigonal planar molecules
CH2O
BH3
BeF2
127
What are some bent molecules
SH2
| O3
128
What are some linear molecules
BF2
| CO2
129
For elements Z =/> 21 the energy of the 3D sub shell is...
Higher than the energy of the 4S sub shell
130
Describe the second ionise energy of potassium and why it bucks the trend
Involves the removal of an electron from a full 3P^6 stable arrangement and therefore has a relatively high second ionisation energy
131
Describe the second ionise energy of chromium and why it bucks the trend
Involves the removal of an electron from a 3d^5 stable arrangement and therefore has a relatively high second ionisation energy
132
Describe the second ionise energy of chromium and why it bucks the trend
Involves the removal of an electron from a full 3d^10 stable arrangement and therefore has a relatively high second ionisation energy
133
Describe the third ionise energy of potassium and why it bucks the trend
The third electron is being removed from an inner sub shell subject to a lesser degree of electron shielding and a greater nuclear electrostatic force of attraction
134
Describe the third ionise energy of calcium and why it bucks the trend
Involves the removal of an electron from a full 3p^6 stable arrangement and therefore has a relatively high second ionisation energy
135
Describe the third ionise energy of manganese and why it bucks the trend
Involves the removal of an electron from a 3d^5 stable arrangement and therefore has a relatively high second ionisation energy
136
Describe the fourth ionisation energy of potassium and Calcium and why it bucks the trend
The fourth electron is being removed from an inner sub shell subject to a lesser degree of electron shielding and a greater nuclear electrostatic force of attraction
137
Describe the fourth ionisation energy of scandium and why it bucks the trend
Involves the removal of an electron from a full 3p^6 stable arrangement and therefore has a relatively high second ionisation energy
138
Describe the fourth ionisation energy of iron and why it bucks the trend
Involves the removal of an electron from a 3d^5 stable arrangement and therefore has a relatively high second ionisation energy
139
Molecular formula
The number of different atoms in a formula
140
Structural formula
How the different atoms are arranged
141
Empirical formula
The simple whole number ratio of atoms in a molecule
142
Skeletal formula
Show how the carbon-carbon bond and functional groups are arranged.
Neither the carbon atoms or the hydrogen atoms attached to the carbon atoms
143
Atomic orbitals
The volume of space that the electrons of atoms are likely to be found
144
When atomic orbitals overlap, they combine to form....
Molecular orbitals
145
In the case of hydrogen, the overlap of two 1s orbitals results in the formation of a
sigma ( σ) molecule
146
The shape of the molecular orbital formed from overlapping orbitals will govern
The type of intermolecular bonding that is observed
147
Hybridisation
Assumes that the 2s and 2p orbitals of carbon atoms combine to form four degenerate orbitals
The sp^3 orbitals formed are half filled
148
Sp^3 hybridised orbitals surrounding a central carbon atom results in a
tetrahedral shape with a maximum possible angle between each orbital of 109.5
149
Carbon to carbon single bonds in alkanes result from...
Overlapping sp^3 orbitals forming σ bonds
150
Double bonds are stronger but not twice as strong as σ bonds, this is because
They are made up of both a σ bond and a pie bond and sideways overlap (pie bond) is weaker than σ
151
Hybridisation of Alkenes
An electron from the 2s shell is promoted to the 2p orbital. This results in the formation of three hybrid orbitals with one remaining unhybridised
Remaining 2p orbital
Formed from one s orbital and 2p orbitals is the sp^2 orbital
152
Sp2 orbitals take a .....shape
Trigonal planar (bond angle 120°)
153
In alkenes, Three sp^2 orbitals form sigma bonds with two hydrogen atoms and the other carbon atom. The unhybridised 2p orbital....
Overlap side on to form a pi bond
154
What is the colour of organic compounds that contain only sigma bonds...
Colourless
155
Why are organic compounds that contain only sigma bonds colourless
The σ bonding orbital is the HOMO and the σ* anti-bonding orbital is the LUMO
While they do absorb light the energy transition is very large (eg in the uv range)
156
HOMO
Highest Occupied Molecular Orbital
157
LUMO
Lowest Unoccupied Molecular Orbital
158
When the transition from HOMO to LUMO is large the colour of the compound will absorb in...
The UV region of the spectrum
159
Conjugated system
Organic molecules that are coloured contain delocalised electrons spread over a number of atoms
Alternating double and single bonds
160
The longer the conjugated system the smaller....
The energy gap between the delocalised orbital and the next unoccupied orbital
161
Why are conjugated systems coloured
Exciting delocalised electronic requires less energy. If this falls within the visible part of the electromagnetic spectrum it will result in the compounds appeared coloured
162
Chromophore
A group of atoms with a molecule that is responsible for its colour
163
If the chromophore absorbs light of one colour ...
The complimentary colour is observed
164
Dative bond
When both electrons in a covalent bond come from the same atom
165
Resonance forms
Sometimes it is possible to draw more than one equivalent Lewis dot diagram for a single structure
The actual molecule is a hybrid of the resonance forms
166
Resonance structure
And average of the resonance forms
167
Why do transition metals have variable valences
Can loose 4S electrons and some or all of their 4D electrons to form positive ions
168
What ions does scandium form
3+ ions
169
What ions does zinc form
2+ ions
170
bond fission
when an organic reaction takes place, bonds in the reactant molecules are broken and bonds in the product molecules are made
171
homolytic fission
more likely when the bond is Non polar
sigma bond breaks evenly
it results in the formation of two neutral free radicals (atoms with unpaired electrons)
172
heterolytic
this type of bond breaking is more likely when the bond is Polar
sigma bond breaks unevenly
results in the formation of positive and negative ions
the atoms with the largest electronegativity willa end up with both electrons
173
reactions involving homolytic fission are unsuitable for organic synthesis as...
they tend to result in the formation of very complex mixtures of products.
heterolytic fissions result in far fewer products and so are better suited
174
a single headed arrow shows the movement of ...
a single electron
175
a double headed arrow shows the movement of ...
a pair of electrons
176
the tail of a curly arrow shows...
where the electron/ pair of electrons originates
177
single headed curly arrows tend to show the movement of electrons in...
Homolytic fission
178
double headed curly arrows tend to show the movement of electrons in...
heterolytic fission
179
in reactions involving heterolytic bond fission, attacking groups are classified as....
nucleophiles or electrophiles
180
nucleophiles can be
negatively charged ions or neutral molecules that re electron rich
attracted towards atoms bearing partial or full positive charge
capable of donating an electron pair to form a new covalent bond
181
electrophiles can be
positively charged ions or neutral molecules that re electron deficient
attracted towards atoms bearing partial or full negative charge
capable of accepting an electron pair to form a new covalent bond
182
positively charged Carbocation
electrophile important as a reaction intermediate in many organic processes
vey unstable as it does not have a share of eight electrons
only makes three bonds
(unlikely for a carbon atom)
any situation which reduces the effective size of the positive charge on the carbon atom will stabilise the charge
183
Tertiary carbocations are the most stable because...
they have more carbon atoms attached to the positively charged carbon atom and consequently have more electrons that can be attracted to the positive charge. this stabilises the ion
184
addition reaction
normally happen when reactants are added across the double bond of alkenes or triple bonds of alkynes
in a typical reaction a small molecule is added to an alkene or alkyne.
185
hydrogenation
two hydrogen atoms are added in an addition reaction
186
hydration
a water molecule is added in an addition reaction
187
hydroHalogenation
a hydrogen and a halogen atom are added in an addition reaction
188
halogenation
two halogen atoms are added in an addition reaction
189
the test for unsaturation is...
bromine water
| an addition reaction
190
haloalkanes
organic compounds which contain one or more halogen atoms
191
to add water across the double bond you need an
acidic catalyst
192
when alkenes and alkynes that contain more than two carbon atoms react with a small molecule ….
more than one product might form. if the two atoms being added to the alkene are different they each can be placed on the two carbons involved in the double bond
193
markovnikov's rule
the hydrogen atom of the small molecule will attach to the carbon of the double bond that is already bonded to the most hydrogen atoms
194
elimination reaction
atoms are removed from an organic molecule and a double bond forms between the carbon atoms from which the atoms were removed
usually loses two atoms and the two products are formed
195
the dehydration of alcohols to produce alkenes is an example of an
elimination reaction
196
the dehydration of alcohols to produce alkenes requires...
a catalyst of concentrated sulphuric acid or concentrated phosphoric acid or aluminium oxide
197
if an asymmetrical alcohol like butan-2-ol undergoes an elimination reaction...
two products are formed (but-1-ene and but-2-2ene)
198
the removal of atoms on adjacent atoms of a haloalkane is an example of...
an elimination reaction
199
the removal of atoms on adjacent atoms of a haloalkane requires...
a strong alkali such as sodium hydroxide dissolved in ethanol
200
elimination reactions involving either alcohols or haloalkanes is a way of producing
alkenes (produced by heating under reflux)
