Organic Flashcards
1
Q
Hydrocarbon
A
A compound that contains only hydrogen and carbon atoms
2
Q
Homologous series
A
A family of compounds containing the same functional group but with each successive member of the series differing by a CH2 group
3
Q
Functional group
A
An atom/ group responsible for the characteristic reactions of the compound
4
Q
Aromatic
A
Compound containing a benzene ring
5
Q
Aliphatic
A
Compounds of carbon and hydrogen joined together in straight chains, branched chains or non aromatic rings
6
Q
Alicyclic
A
Aliphatic compounds arranged in non aromatic rings with or without side chains
7
Q
Prop
A
3
8
Q
But
A
4
9
Q
Structural isomerism
A
Molecules with the same molecular formula but a different structural formula
10
Q
Himolytic fission
A
The breaking of a covalent bond where one electron from the bonding pair goes to each to atom to form two radicals
11
Q
Heterolytic fission
A
The breaking of a covalent bond where on bonding atom receives both electrons from the bonding pair to form 2 ions with opposite charges
12
Q
Bonding in alkanes
4
A
Saturated hydrocarbons
C-C and C-H are made up of sigma bond
Sigma bond is formed between two carbon atoms by the direct single overlap of orbitals directly between bonding atoms
This allows free rotation of sigma bond
13
Q
Carbon chain length - alkanes BP
4
A
As the chain length increase so does the boiling point
More surface contact between molecules
More induced dipole-dipole interactions betweeen the molecules
More energy needed to overcome them
14
Q
Branching- alkanes BP
3
A
A branched isomer has a lower boiling point than an unbranded
When it’s more branched there is less surface contact between molecules so less induced dipole dipole interactions
Less energy needed to break the weaker induced dipole dipole interaction between the molecules
15
Q
Alkanes are relatively unreactive because
A
Sigma bonds are
Non polar
Strong
16
Q
Combustion of alkanes
4
A
Exotherimic
Useful as fuels
Plentiful oxygen= CO2 and H2O
Limited oxygen= CO and H2O
17
Q
Radical substitution
A
Reagents: halogen and excess alkane
Conditions: UV radiation
18
Q
Radical
A
A species with an unpaired electron.
19
Q
Substitution
A
Reaction where an atom or a group in a molecule is replaced by another atom or group
20
Q
Electrophile
A
Electron pair acceptor
21
Q
Nucleophile
A
Electron pair donor
22
Q
Addition
A
A reaction where a group is added across a double bond of an unsaturated molecule to make a saturated molecule
One product
23
Q
Limitation of radical substitution
6
A
Mixture of products
Further substitution leads to a mixture of halegenoalkanes
Structural isomers
Low % yield of halegenoalkanes
Separation by fractional distillation is costly
Excess methane is used to avoid further substitution
24
Q
Bonding in alkenes
A
C=C double bond is made of pi and sigma bond
Restricted rotation of pi bond
Sigma bond is formed directly between two carbon atoms by the head on single overlap of orbitals directly between bonding atoms
Pi bond is formed by the double sideways overlap of adjacent p orbital above and below c atoms
25
Stereoisomers
Compounds with the same structural formula but with a different arrangement of the atoms in space
26
Criteria for E/Z isomerism
Must have a carbon carbon double bond as this cannot rotate
Each carbon of the C=C must have two different groups attached to it
27
Additional criteria for cis / trans
Two groups on the c=c bond must be Identical
28
Alkenes are more reactive than alkanes because
C=c bond
29
Chemical test for alkene functional group
Add bromine and shake
Decolourised = Alkene
30
Alkene + H2
Electrophilic addition
Nickel catalyst
150 degrees
31
Alkene + halide Br2
Electrophilic addition
No catalyst
Room temp
32
Alkene + hydrogen halide
Electrophilic addition
No catalyst
Room temperature
33
Alkene + steam H2O
Electrophilic addition
Conc. phosphoric acid catalyst
High temp
High pressure
34
Curly arrow
Shows the movement of an electron pair to either break or make a covalent bond
35
Major and minor products
Primary (least stable)(minor)
Secondary
Tertiary (most stable) (major)
The more alkyl groups attached, the more the charge is spread out making the ion more stable
36
Addition polymerisation
Reagents: Alkene monomer
Condition: high temp & pressure, catalyst
37
Problems with disposal of addition polymers
| 2
Non biodegradable. C chain is non polar so cannot be broken by hydrolysis.
Burning produces toxic gases(chloro gases)
38
Processing waste addition polymers
| 4
Combustion for energy products
Removal of toxic waste products
Use as an organic feedstock for the production of plastics and other organic chemicals
Recycled
39
Role of chemists in minimising environmental damage
| 3
Biodegradable polymers- can be broken down by microorganisms in water
Photodegradable polymers- weakened by light
Alkaline scrubber- neutralise toxic HCl gas
40
Hydration of ethene
Reagents: steam+ ethene
Conditions: H3PO4 catalyst, high temp& pressure
Use of ethanol: as a solvent and chemical feedstock
100% yield and atom economy
Fast rate of reaction
Pure product
Expensive/ high energy
Comes from crude oil= non renewable
41
Fermentation of sugars
Reagents: glucose
Condition: enzyme( in yeast) 37 degrees
Use of ethanol: alcohol
51% atom economy as produces CO2
7-14% yield
Cheap, easy and renewable as come from sugar cane
CO2 by product, low yield, slow reaction
42
Solubility of alcohol
| 4
Dissolve in water as there is a polar -OH group which forms hydrogen bond with polar H2O molecules
First three members are soluble
Solubility decrease as chain length increases because
A larger part of the molecule is made up of non polar hydrocarbon chain which doesn’t form hydrogen bonds with water
43
Boiling point of alcohols
Higher than alkanes
Hydrogen bonds are very strong and need Lots if energy to overcome them
Stronger than London forces
44
Dehydration of alcohols
Reagents: conc. acid
Condition: heat under reflux
Where a H2O molecule is removed form a saturated molecule to form an unsaturated molecule
45
Oxidation of primary alcohol
Acidified dichromate
Distillation
Aldehyde + h20
46
Further oxidation Of primary alcohol
Carboxyl is acid
Reflux
47
Oxidation of secondary alcohol
Reflux
Ketone
48
Nucleophilic substitution
NaBr and H2SO4 makes HBr in situ
Reflux
49
When a covalent bond absorbs Infared
It vibrates more
50
Nucleophilic substitution
Reflux
51
Reactivity of haloalkanes
Increases down group
52
Rate Of hydrolysis of haloalkanes
Increases down groups as bonds get weaker
53
Ozone
Learn
54
Solubility of carboxylic acids
First four are soluble
Hydrogen bond forms
As R group increases, solubility decreases as
Carboxyl groups is polar
Hydrocarbon chain is non polar
55
Acidity of carboxylic acids
Acids are proton donors
Carboxylic acids are weak acids so only partially dissociate
56
Significance of Ka
Large= greater than 1, strong acid
Small= less than 1, weak acid
57
Preparing an ester from a carboxylic acid and ester
Conc H2SO4, catalyst and heat
Estérification
58
Nucleophilic substitution reaction
Am electron pair donor replaces a halogen atom
59
Why is the rate of hydrolysis of 1-iodobutane faster than the rate of hydrolysis of 1-chlorobutane
The rate of hydrolysis depends upon the strength of the carbon-halogen bond
The C-I bond is weaker than the C-Cl bond
Less energy is needed to break the C-I bond so the rate of hydrolysis is faster
60
Uses of halogen compounds
| 2
To make polymers
As chlorofluorocarbons
61
CFCs
Chlorofluorocarbons
3+3
Inert
Non toxic
Non flammable
Once used as refrigerants, aerosols
No longer used as they result in depletion of ozone
Have now developed HFCs
62
Evidence against the kekule model
| 3
1. Resistance to reaction- benzene doesnt decolourise Br2 at room temperature = benzene doesnt contain c=c bonds and is less reactive than expected
2. Bond lengths from X-ray diffraction analysis- all C to C bond lengths are the same - the C to C bond length is between that of the C-C single bond and C=C double bond = benzene does not contain isolated, alternating c-c or c=c bonds
3. The enthalpy change for hydrogenation-
* learn to equations* == benzene does not contain 3 c=c bonds. Benzene s more stable than expected.
63
Delocalised structure of benzene
| 5
Benzene is a cyclic molecule- a closed ring of 6 C atoms
The shape around each C atom is triagonal planar with a H-C-C bond angle of 120 degrees
There are sigma bonds between the C atoms and between the C-H atoms, which are formed by single overlap of orbitals directly between the C atoms
There is one pi system above and below the plane of the C ring, which is formed by the sideways double overlap of p orbitals on each C atom of the C ring
The pi system contains 6 delocalised electrons, which are mobile across all 6 Catoms of the benzene ring
64
2 similarities and 2 differences of the pi bond in cyclohexene with the pi system inn benzene
Similarities;
1. The pi bond is formed by the double sideways overlap of a p orbital on each C atom involved in the pi bond
2. The pi bond is above and below the plane of the C atoms involved in the pi bond
Differences;
1. In benzene,the pi system is made up of 6 electrons whereas in cyclohexene the pi bond is only made up of 2 electrons
2. In benzene the pi system electrons are delocalised across all 6 C atoms, whereas in cyclohexene, the pi bond electrons are localised across 2 C atoms
65
Why is cyclohexene more reactive towards electrophiles such as bromine than benzene
3
The pi bond in an alkene is more is more electron dense than the pi system in benzene
Because the 2pi electrons in an alkene are localised between 2 C atoms, whereas the 6pi electrons are delocalised across alll 6 C atoms in benzene
The pi bond in the alkene is sufficiently electron dense to induce a dipole in the Br2 molecule and so attracts electrophiles more strongly
66
The intermediate and the organic product have different structures as shown below. Both structures have a pi bond
Deduce how many electrons are involved in the pibonding in each structure and describe how their arrangements are different
Carbocation intermediate has 4 electrons in pi system.
Delocalised about 5 C atoms of the ring
The product contains 6 electrons in the pi system
Delocalised about all 6 C atoms of the benzene ring
67
The nitration of benzene
Reagents; concentrated nitric acid
| Conditions; cncentratedsulfric acid, heat u der reflux at 50 degrees C
68
The chlorination of benzene
Reagents; chlorine gas
| Conditions; iron (III) chloride, iron or aluminium chloride
69
The bromination of benzene
Reagents; bromine liquid
| Conditions; iron (III) bromide, iron or aluminium bromide
70
The alkylation of benzene
Reagents; halo alkane
| Conditions; aluminium chloride
71
The acylation of benzene
Reagents; acyl chloride
| Conditions; aluminium chloride
72
Ortho
Position 2
73
Meta
Position 3
74
Para
Position 4
75
Electron donating groups
Make the pi system more electron dense making the ring more susceptible to attack by electrophiles
- more reactive
76
Electron withdrawing group
Make the pi system less electron dense making the ring less susceptible to attack by electrophiles
-less reactive
77
Phenol can undergo reaction involving either part of the phenol functional group
1. Reactions of phenol involving the benzene ring - electrophilic substitution . Phenols are more reactive than benzene and the reactions of phenols take place more readily and under milder conditions
2. Reactions of phenol as an acid
78
Nitration of phenol
Reagents; dilute nitric acid
| Conditions; room temperature
79
Bromination of phenol
Reagents; bromine water
| Conditions; room temperature
80
Phenol is more reactive than benzene because
| 3
In phenol the lone pair of electrons on the p orbital of the oxygen atom is donated and becomes partially delocalised into the pi bond
The pi bond in phenol is more electron dense than the pi bond in benzene
The pi bond is sufficiently electron dense to induce a dipole and so attracts electrophiles more strongly
81
Reactions of phenol as an acid
Phenol is a weak acid
The acidic hydrogen is the H bonded to oxygen in the phenol group
When dissolved in water, phenol partially disassociates as a proton donor
Phenol is a weak acid so can react with basic substances to form phenoxide salts. Eh NaOH
Doesnt react with carbonates, ammonia etc as they are stronger weak acids
82
Phenol + acyl chloride
Ester + HCl
83
Phenol + acid anhydride
Ester + carboxylic acid
84
Carbonyl group
C=O
85
Aldehydes
The C atom of the aldehyde group is always C1, at least one H attached
Suffix -al
86
Ketones
Two carbons attached yo the carbonyl group
| Suffix -one
87
Structure of the carbonyl group
Consist of a carbon-oxygen doubl bond
The C=O bond is polar because O is more electronegative than C
The C atom forms three sigma bonds, arranged in a trigonal planar sape. Bond angle about C is 120 degrees
There is a pi bond above and below the plane of the C-O sigma bond formed by double sideways overlap of p orbitals
88
Preparing aldehydes and ketones from primary and secondary alcohols
Oxidation
| Oxidising agent [O] of acidified sodium or potassium dichromate
89
Forming alcohols from aldehydes and ketones
| Nucleophilic addition
Reduction
Reducing agent[H]
Reagents; aqueous sodium tetrahydridoborate(III), NaBH4
Conditions; solvent is water/ in aqueous solution, warm
Reaction type; nucleophilic addition
NaBH4– BH4- provides hydride H- ions which act as a nucleophilic
90
Reaction of aldehydes and ketones with hydrogen cyanide HCN
Reagent; NaCN and H2SO4 ( which make HCN in-situ)
Conditions; solvent is water/ in aqueous solution, carried out in fume cupboard(HCN is highly toxic gas)
Nucleophilic addition
Produces hydro unit tiles
HCN is a weak acid which partially dissociates in water to produce the CN_ ion which acts as a nucleophile
91
Nitrile groups are readily hydrolysed by acid hydrolysis to form carboxylic acids
Reagent; aqueous acid eg HCl or H2SO4
Conditions ; solvent is water/ in aqeous solution, warm/ heat under reflux
Reaction type; acid hydrolysis
92
Chemical test for an aldehyde
Tollens reagent- weak oxidising agent so can only oxidise aldehydes
Tollens= mixture of ammonia and silver nitrate
As an equal volume of tollens reagent to the compound and place boiling tube into water bath for 5-10 mins
Silver mirror precipitate formed
Silver ions are the oxidising species reduced to silver atoms
Aldehyde is oxidised to carboxylic acid
93
Test for any carbonyl
2,4- dinitrophenylhydrazine
Add an excess
Deep yellow or orange precipitate is formed
94
Solubility of carboxylic acids
```
Lower carboxylics (C 1-4) are double in water.
The carboxylate group is polar and attracts water molecules. The polar carboxyl group forms hydrogen bonds with water molecules
```
As t5he size of the hydrocarbon R group increases, the solubility in water decreases because;
The carboxyl group is polar and hydrogen bonds with H2O
The hydrocarbon chain is non polar/ hydrophobic
A greater proportion of the molecule is non polar as the size of the hydrocarbon group increases.
95
Acidity of carboxylic acids
Acids are proton donors- release H+ ions in aqueous solution
Carboxylic acid is a weak acid so partially dissociates into its ions in solution
Equilibrium position is far to the left
Concentration of protons (H+) is low, compared with the concentration of the undissociated acid
96
Acid dissociation constant Ka=
Ka=
[H+][A-] / [HA]
97
The significance of the value Ka
If Ka is a large number;
[H+] and {A-] are large
The equilibrium position is far to the right
Ka>1
A lot of the HA acid is dissociated into its ions
STRONG ACID
```
If Ka is a small number;
[H+] and [A-] are small
The equilibrium position is far to the left
Ka<1
A lot of the HA acid is not dissociated
WEAK ACID
```
98
Estérification
Forms an ester
Reagents; a carboxylic acid + alcohol
Conditions; concentrated H2SO4 catalyst and heat
Condensation reaction
Reversible reaction
Low yield
99
Naming an ester
Carboxylic part= ‘alkanoate’
| Alcohol part= ‘alkyl’
100
Naming acyl chlorides
Suffix -oyl
101
Preparation of acyl chlorides
Carboxylic acid is reacted with SOCl2
CH3COOH + SOCl2 —> CH3COCl + SO2 + HCl
Must be done under anhydrous conditions as ethanol chloride reacts readily with water
102
A drying agent
An anhydrous inorganic salt that readily takes up water to become hydrated.
103
Reactions of acyl chlorides
Highly reactive and can be easily converted into a number of different products
React with nucleophiles due to the high delta positive charge on the carbon atom.
The nucleophile is attracted to the delta positive carbon and acts as an electron pair donor.
Molecules which have a lone pair which can be donated react readily with acyl chlorides
104
Reaction of acyl chlorides wit water
Carboxylic acid + HCl
Extremely vigorous reaction at room temperature
105
Reaction of acyl chlorides with alcohols
Ester + HCl
Efficient reaction for producing an ester as it happens at room temperature and is not reversible so higher yield
106
Preparation of an ester from an acid anhydride and an alcohol
Reagents; an acid anhydride + alcohol
Conditions; gentle heat and anhydrous conditions
Better yield of ester than from a carboxylic acid as reaction is irreversible
107
Hydrolysis of an ester
Hydrolysis is the breaking of a covalent bond by its reaction with water ( can be acid or base catalysed)
108
When an ester is hydrolysed
The polar ester group (-COO-) reacts with polar H2O and the C-O sigma bond of the ester group breaks
109
Acid catalysed hydrolysis
Reagents; aqueous acid eg HCl or H2SO4
Conditions; heat under reflux
The C-O covalent bond of the ester breaks to form a carboxylic acid and an alcohol
Reversible
110
Base catalysed hydrolysis
Reagents; aqueous alkali eh NaOH or KOH
Conditions; heat under reflux
The C-O covalent bond of the ester breaks to form the salt of the carboxylic acid and an alcohol
Irreversible
111
Stereoisomers
Have the same structural formula but different spatial arrangements of their atoms
112
Optical isomers
A pair f non-superimposable mirror images of one another
113
A chiral centre
A carbon atom with fou different groups attached
114
Enantiomers
A pair of optical isomers
115
NMR spectroscopy involves
The interaction of materials with the low-energy radio wave region of the electromagnetic spectrum
116
2 features of C-13 NMR
The value of “” (chemical shift) = the type of C
The number of peaks= number of different C environments
117
4 features of a H-1 NMR spectrum
The value of the chemical shift value= identifies the type of H environments
The number of peaks= number of different H environments in the molecule
The relative area under each peak = relative numbers of H in each environment
Spin-spin splitting pattern of each peak= the number of non equivalent H on the adjacent C atoms t a given proton
Splitting pattern= n+1
118
Singlet
N=0
| N=1=1
119
Doublet
N=1
| n+1=2
120
Triplet
N=2
| N+1= 3
121
Quartet
N=3
| N+1= 4
122
Multiplet
N=4
| N+1=5
123
What are amines
Derivative of ammonia
Can be classified as primary,secondary or tertiary
124
Why are amines weak bases
They only partially dissociate into their ions in solution
125
How does an amine act as a base
The N atom donates it lone pair
To form a dative covalent bond with a proton, H+
The amine is a proton acceptor
126
Preparation of an aliphatic amine
| Method A
Reagents; ammonia and halo alkane
Conditions; excess ammonia dissolved in ethanol (ethanolic ammonia)
Reaction type; nucleophilic substitution
Can undergo further substitution
127
Preparation of an aliphatic amine
| Method B
Reagents; nitrile, hydrogen, H2 in the presence of...
Conditions; ...nickel catalyst
Reaction type; reduction
128
Preparation of an aromatic amine
Reagents; nitroarene,tin, conc. HCl
Conditions; heat under reflux
Reaction type; reduction
129
Amide functions group
R-CON
Can be primary, secondary or tertiary
130
Production of amides
| 3
Acyl chloride+ammonia->primary amide
Acyl chloride+amine->secondary amide
Carboxylic acid+amine->secondary amide
131
Acid- catalysed hydrolysis
| Nc
Reagent; aqueous acid eg HCl
Conditions; heat
Products= carboxylic acid + ammonium salt of the amine
132
Base- catalysed hydrolysisNC
Reagent; aqueous alkali eh NaOH
Conditions; heat
Products= carboxylic acid + an amine
