A2 Chemistry 2021 Flashcards
(119 cards)
1
Q
What is the bond angle in benzene
A
120
2
Q
Why is benzene more stable than triene
A
Benzene has delocalised electrons in a pi system which are spread out, minimising repulsion.
3
Q
What is the difference in energy required to react between benzene and triene called
A
Resonance energy
4
Q
Reagents and conditions for nitration
A
Conc HNO3, Conc H2SO4, 50*C
5
Q
What are uses of the products of nitration
A
Used to make TNT or dyes.
6
Q
Reagents and conditions for Friedel-Crafts reaction
A
Acyl Chloride, AlCl3, Anhydrous
7
Q
What is the electrophile in Friedel-crafts reaction
A
RCO+ (acylium ion)
8
Q
Reagents and conditions for Halogenation
A
AlCl3 or FeCl3 catalyst, Anhydrous
9
Q
Reagents and conditions for alkylation
A
AlCl3 or FeCl3 catalyst, Anhydrous
10
Q
Why is phenol a weak acid
A
The electrons from the oxygen atom get delocalised into the pi system of the benzene ring, making the phenoxide ion more stable.
11
Q
What is the difference between an aromatic alcohol and phenol
A
The oxygen atom in phenol is bonded directly to the benzene ring.
12
Q
Reagents and conditions for diazotisation
A
Phenylamine, HNO2 or NaNO2, HCl, <10*C
13
Q
4 stages to make phenol from benzene
A
1) Nitration
2) Reduction
3) Diazotisation
4) Substitution
14
Q
What is formed when phenol reacts with sodium
A
Sodium Phenoxide ion, Hydrogen gas
15
Q
Why does Br attach to the 2,4,6 positions on phenol
A
As the -OH group is electron releasing, it increases the electron density in the 2,4,6 positions
16
Q
Reagents and conditions for nitration of phenol
A
Dilute HNO3, Room temp
17
Q
How is acyl chloride formed
A
By adding PCl5, PCl3, SOCl2 to carboxylic acids.
18
Q
What is formed when PCl5 reacts with carboxylic acids
A
POCl3 + HCl
19
Q
What is formed when PCl3 reacts with carboxylic acids
A
H3PO4
20
Q
What is formed when SOCl2 reacts with carboxylic acids
A
SO2 + HCl
21
Q
Why do acyl chlorides have high B.p
A
C-Cl bond has permanent dipole due to polarity
22
Q
Reagents and conditions for making amines from halogenoalkanes
A
Halogenoalkane + Hot, Ethanolic NH3
23
Q
Why is Hot ethanolic NH3 used to make amines
A
To prevent the formation of 2* or 3* amines
24
Q
Reagents and conditions for making amines from nitriles
A
Step 1: KCN/HCN in ethanol, heated under reflux with halogenoalkane
Step 2: Hydrogen with Ni catalyst, pass vapours over dry ether
25
What is observed when phenylamide is added to bromine water
Bromine water decolourises and a white precipitate is formed
26
Why are amines good bases
The nitrogen atom has a lone pair of electrons available to bond with a H+ ion
27
Why is ammonia not basic
The nitrogen atom does not have a lone pair of electrons available to bond with H+
28
Reagents for triiodomethane reaction
Aqueous alkaline Iodine, NaOH
29
Why must diazotisation be done at <10*C
The diazonium ion formed is very reactive
30
Which position does coupling usually occur in
4
31
What is reacted to form nitrous acid
NaNO2, HCl
32
When azo compounds are formed why do they always join in the 4 position
Phenol is a ring activating group
33
Why are amides pH neutral
The lone pair of electrons from the nitrogen are delocalised alongside the electrons from the oxygen, making the ability to attract H+ non-existent
34
What is reacted to form amides
Acyl chlorides with amines
35
What is formed when HCl is reacted with excess ammonia
NH4Cl
36
What is reacted with amides to form amines
LiAlH4
37
What is formed by the reaction of amides with acids
- Carboxylic acids
| - Ammonium or RNH3+ ions
38
What is formed by the reaction of amides with bases
- Acid salts
| - Amines/Ammonia
39
What is the bond between amino acids called
Peptide bond
40
What is reacted to form amino acids
Amine + Carboxylic acid
41
What is formed form the reaction between Amine + carboxylic acid
Amino acids
42
What is a zwitterion
Amino acid with H moved from O to N;
| -ve charge on O, +ve charge on N
43
Do elements with higher E* value get oxidised or reduces more easily
Reduced
44
On which side of the cell does the more positive electrode go
Right side
45
How do you know if an electrolysis reaction is feasible
The emf value (RHS-LHS) is positive
46
At the positive electrode, which side of the half equation does the equilibrium sit
Left
47
What is the name for two combined half cells
Electrochemical cell
48
State the representation of the standard hydrogen electrode
Pt(s) | H2(g) | H+(aq)
49
If there are no solid elements in a half cell, what is the electrode made of
Pt(s)
50
What are the standard conditions
298K, 100kPa, 1M soln.
51
On which side of the electrolysis reaction does the S.H.E sit
Left side
52
What is the charge on 1 mole of e-
96500C
53
How many coulombs in 1F
96500C
54
What is a transition metal
A d-block element which forms one or more stable ions with incomplete d-orbitals.
55
Why do 4s orbitals fill up before 3d orbitals.
Because they are lower in energy
56
What are the 2 exceptions in the aufbau rule
Copper: [Ar]3d10,4s1
Chromium: [Ar]3d5,4s1
57
Why are there 2 exceptions in the aufbau principle
More repulsion is caused by filling 4s sub shell.
| Filling 3d sub shell provides more shielding to nucleus
58
Which 'transition metals' are not actually considered transition metals
Scandium, Zinc
59
What causes elements to have colour
Incomplete d-orbitals.
60
What is an orbital
A region in which there is an extremely high probability of finding an electron
61
Which d orbitals lie in between axis
dxy, dyz, dxz
62
Which d orbitals lie on the axis
dx2-y2, dz2
63
What is a ligand
A base with a lone pair of electrons which forms a dative bond with a central metal atom
64
What is a bronstead acid/base
Proton donor/acceptor
65
What is a lewis acid/base
Lone pair donor/acceptor
66
What is a complex ion
A molecule or ion formed by a metal atom surrounded by 1 or more ligands
67
Why are transition metals attractive to nucleophiles
They are relatively small and have a high charge density.
68
What is meant by coordination number
The number of dative covalent bonds in a complex ion
69
Why can complex sometimes only make 4 bonds
Due to steric hinderance eg Cl which is high charge density
70
What is the coordination number of silver
2
71
What are monodentate ligands
Ligand bonds to the metal with only 1 covalent bond.
72
What are chelates
They bond to the metal ion in two different locations forming a ring
73
What is the change in entropy when a chelate bonds to a complex ion
Increase
74
What is the bond angle in a cis isomer of a complex ion
90 degrees
75
If the bond angle in a complex ion is 180 degrees, what type of isomer is it
trans isomer
76
What colour is a complex ion containing the OH- ligand
Pale blue
77
What colour is a complex ion containing the H2O ligand
Deep blue
78
What colour is a complex ion containing the Cl ligand
Green
79
What colour is anhydrous CuSO4
White
80
What is formed when the NH3 ligand is added to the copper complex ion
Blue ppt.
81
What is a chelating agent
Ligands which form more than 1 dative bond
82
If coordination number decreases, entropy _______
decreases
83
If a complex ion solution is higher concentration, will it absorb more or less colour?
More
84
What causes coloured compounds?
Ligands cause repulsion which causes orbitals to split. This allows electrons in partially filled d orbitals to absorb light energy and move between 2 non-degenerate orbitals and reflect light.
85
What is a non-degenerate orbital
Orbitals which have been split due to the repulsion of ligands and consequently have different energy levels.
86
When octahedral complex ions split, does the energy levels of the orbitals increase or decrease?
Increase
87
When octahedral complex ions split, which orbitals are at a lower energy level
dxy, dyz, dxz
88
What is the energy gap size between higher and lower energy level orbitals dependant on
Wavelength of light absorbed
89
What is Kstab
The equilibrium constant for the overall reaction
90
If Kstab of a reaction is more +ve, is it more or less stable?
More
91
What is a polymer
A long chain molecule made from lots of small molecules joined together.
92
What are the 2 types of polymerisation
Addition, Condensation
93
What is reacted to form polyamides
Dicarboxylic acid + diamine
94
What is formed from the polymerisation of amino acids
Polyamides
95
What is reacted to form an ester
Carboxylic acid + alcohol
96
What is reacted to form polyesters
Dicarboxylic acid + diol
97
What is reacted to form an amide
Carboxylic acid + amine
98
Why are condensation polymers generally more rigid than addition polymers?
Due to their polarity which creates H-bonds
99
What is formed when a tertiary carbon is attacked by a photon
Free radical
100
What is the double helix comprised of
2 sugar phosphate backbones linked by base pairs
101
What are the 4 bases in DNA
cytosine
thymine
adenine
guanine
102
Where do the bases attach to the sugar backbones
In place of the -OH on the 1-carbon
103
How is nucleotide formed
Attaching a base to the sugar backbone
104
Outline the DNA replication process
Effectively, the double helix is split between the base pairs, and new bases attach to these split ones.
105
What are proteins comprised of
Amino acids joined together by peptide bonds.
106
What is meant by the primary structure of proteins
Describes the order of amino acids used to make up the protein
107
What is meant by the secondary structure of proteins
Alpha helixes and beta pleated sheets
108
How and where are secondary structures held together
H-bonds between lone pair on O and H attached to N atom
109
What is the shaped of an alpha helix
Protein chain in a loose coil
110
What is the shape of a beta pleated sheet
Protein chains folded alongside eachother
111
What is meant by the tertiary structure of proteins
Describes the way the whole chain (incl. secondary structure) is arranged in it's final 3D shape
112
What types of interactions hold the tertiary structure together
- Ionic interactions
- Hydrogen bonds
- van der waals forces
113
Why does PTFE have a relatively high M.P despite weaker van der waals forces
Because the molecules are essentially straight, they can like very close together, therefore the intermolecular forces are still strong.
114
Why is kevlar extremely strong material
The polymers are arranged in sheets, which allows for strong H-bonds between strands of kevlar.
115
What are the 3 types of adhesive polymers
Silicon containing resins
Epoxy resins
Super glues
116
What makes silicon containing resins strong adhesives
The Si-O-R groups are hydrolysed, causing cross linking between polymers.
117
What makes epoxy resins adhesive
A curing agent such as a diamine is used to crosslink epoxy groups to form large polymers.
118
What makes super glues adhesive
The cyanoacrylate is very polar and is nucleophilic attacked by water molecules, forming large polymer chains.
119
What makes polymers conductive
pi bonds overlap p-orbitals which means there is a high potential for delocalised electrons.
