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Advnced Higher Chemistry > Unit 3 > Flashcards

Unit 3 Flashcards

(58 cards)

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1
Q

How do molecular orbitals form

A

When atomic orbitals join together

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2
Q

What type of molecular bonding arises from end-on overlapping

A

Sigma bonds

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3
Q

What type of molecular bonding arises from side-on overlap

A

Pi bonds

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4
Q

What bond type is stronger, and what does this mean for double bonds

A

Sigma bonds are stronger

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5
Q

Why is it easy for 2s and 2p subshell to hybridise

A

Asd there is only a small energy difference between the two shells, making it easy for an electron to be promoted

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6
Q

What are the three types of hybridisation

A

sp^3, sp^2 and sp

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7
Q

What bonds do sp^3 hybrid orbitals form with each other, and how

A

End-on overlap, forming sigma bonds

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8
Q

What homologous series contains exclusively sp^3 hybridisation

A

Alkanes (saturated hydrocarbons)

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9
Q

What homoloigous series contains sp^2 hybridisation

A

Alkenes (unsaturated hydrocarbons)

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10
Q

What homologous series contains sp hybridisation

A

Alkynes

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11
Q

What is HOMO

A

The highest bonding molecular orbital containing electrons

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12
Q

What is LUMO

A

The lowest unoccupied molecular orbital

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13
Q

What needs to be absorbed to move from HOMO to LUMO

A

Electromagnetic energy

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14
Q

In terms of HOMO and LUMO, why do most organic and saturated molecules appear colourless

A

The energy difference between HOMO and LUMO is quite large, meaning that the energy absorbed corresponds to the ultraviolet region of the spectrum

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15
Q

What is a chromophore?

A

A group of atoms within
a molecule that is responsible for the absorption of light in the visible region of the spectrum, promoting electrons from HOMO to LUMO.

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16
Q

What is a conjugated system in terms of bonding

A

A series of alternating single and double bonds in a molecule. A system of unhybridised p orbitals that overlap side-on to form molecular orbitals

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17
Q

How does a chromophore dictate the colour of a molecule

A

The more atoms in the conjugated system the smaller the energy gap between HOMO and
LUMO. A lower frequency of light (longer wavelength, lower energy) is absorbed by the
compound.

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18
Q

What is bond fission

A

Bond breaking

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19
Q

What is homolytic fission, and what does it form

A

When a bond breaks, the electrons are divided equally to each atom on either side of the bond (1 electron to 1 atom). This forms two free radicals.

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20
Q

What is heterolytic fission, and what does it form

A

When a bond breaks, one atom retains both of the electrons from the bond. Results in two negatively charged ions forming.

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21
Q

How do structural isomers occur

A

When the atoms of the molecule are bonded together in a different order

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22
Q

What are stereo isomers

A

When the order of the bonding atoms is the same, but the spatial arrangement of the atoms in each isomer is different

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23
Q

What are the two types of stereo isomers

A

Geometric and optical

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24
Q

How does geometric isomerism occur

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A

When there is restricted rotation somewhere in a molecule. Often due to the pi bond in a carbon to carbon double bond

25
How can a cis isomer be defined
When the groups of a molecule are locked onto the same side of the bond, and cannot be moved. (cis, same)
26
How can a trans isomer be defined
When the groups are locked on opposite sides of the bond. (trans, different)
27
Why do trans isomers have a higher melting point than cis isomers
In trans isomers, their straight shape allows them to pack more efficiently, forming stronger intermolecular forces and requiring more energy to break apart.
28
What is a chiral carbon
A carbon with four different groups arranged tetrahedrally around the central atom
29
What type of isomer does a chiral carbon create
An optical isomer
30
Are optical isomers symmetrical or asymmetrical
Asymmetrical
31
What are enantiomers
The two optical isomers that are mirror images of each other
32
How do optical isomers affect light
They rotate the plane of polarisation of light, rotating it either left (+ form) or right (- form) The + and - forms are enantiomers f each other.
33
What is a racemic mixture, and why is it optically inactive
A mixture of equal quantities of the same concentration of two enantiomers. It is an optically inactive mixture, as the two effects on plane-polarised light cancel each other out.
34
What is elemental microanalysis used to determine
The masses of C, H, O, S, and N in a sample of an organic compound in order to determine its empirical formula.
35
What is mass spectrometry used to determine
The accurate gram formula mass (GFM) and structural features of an organic compound
36
How is mass spectrometry performed
A small sample of an organic compound is bombarded by high-energy electrons.
37
What do the high-energy electrons do to the sample
This removes electrons from the organic molecule, generating positively charged molecular ions known as parent ions. These molecular ions then break into smaller positively charged ion fragments. A mass spectrum is obtained.
38
What can the mass to charge ratio be used to determine
The gfm of a molecular ion, and furthermore, the empirical formula of the sample.`
39
What happens to the bonds of an organic molecule when it absorbs infrared radiation
They vibrate (bend and stretch)
40
How is infared spectroscopy perfomed
Infrared radiation is passed through a sample of the organic compound and then into a detector that measures the intensity of the transmitted radiation at different wavelengths. It is similar to colorimetry in this regard.
41
What does proton NMR tell us about a molecule
Gives information on the different chemical environments of hydrogen atoms in an organic molecule, and about how many hydrogen atoms there are in each of these environments.
42
How do low energy 1 H nuclei behave in a strong magnetic field
They align with the magnetic field
43
How do high energy 1 H nuclei behave in a strong magnetic field
They align against the magnetic field
44
What part of the electromagnetic spectrum is used in proton NMR
Radio waves
45
What does the absorption of radio waves do to the protons in an NMR sample
Cause all of the lower energy protons aligned with the magnetic field to flip to align against the field (raising them from low energy to a higher energy).
46
What does proton NMR measure
The energy emitted from the high energy protons as they fall from high energy to low energy after absorbing radio waves.
47
What can be determined from the heights of the peaks on an NMR graph
A ratio of H atoms in each environment
48
What is the reference used in proton NMR
Tetramethylsilane (TMS)
49
In terms of electromagnetic radiation, how does high resolution NMR differ to low resolution NMR
High res NMR uses higher frequency radio waves than low frequency NMR
50
If there were 5 peaks on a high res NMR graph, how many hydrogens would be on the adjacent carbon atoms
4, as calculated by the n+1 rule.
51
How do you calculate the number of hydrogen atoms in an environment based on the NMR graph
Count the number of peaks and minus 1. This is the number of hydrogens the adjacent carbon atom. DO this for all of the groups of peaks.
52
What is a drug
A substance that alters the biochemical processes in the body
53
What do medicines often contain
A filler to add bulk, and sweetners to improve the taste
54
In terms of binding, how do drugs work
By binding to specific protein molecules on the surface of a cell (receptors) or can be specific enzyme molecules within a cell.
55
What is an agonist and how does it work
It binds to the receptor molecules and mimics the natural compound to produce a response similar to the natural compound
56
What is an antagonist and how does it work
It binds to the receptor and blocks the natural compound from binding, preventing the natural signal from being sent
57
How do enzyme inhibitors work
They bind to and block the reaction normally catalysed
58
How does a drug mimic a natural compound
By containing several of the functional groups, oriented correctly, that the drug has. This section of the drug is the pharmacophore.

Advnced Higher Chemistry (4 decks)

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