Topic 6 Flashcards
1
Q
Draw an aldehyde group
A
google it
2
Q
Draw an ester group
A
google it
3
Q
Draw a haloalkane group
A
google it
4
Q
Draw an alcohol group
A
google it
5
Q
Draw an alkene group
A
google it
6
Q
Draw a carboxylic acid group
A
google it
7
Q
Draw a ketone group
A
google it
8
Q
Draw an amine group
A
google it
9
Q
What are aromatic hydrocarbons?
A
Aromatic hydrocarbons are when some or all of the carbons are found in a benzene ring
10
Q
What are aromatic hydrocarbons also called?
A
Arenes
11
Q
What is an alkyl group?
A
An alkyl group has a hydrogen group removed from the alkane chain
12
Q
What are compounds with one substituent group?
A
.These are aromatic compounds with one substituent group that is mono-substituted on to a benzene ring
13
Q
.If the substituent group is: An alkyl group (e.g. CH3), halogen (e.g. Br, Cl), or a nitro group (NO2)
.Then …
A
the parent group is classed as the benzene ring and the group added is considered the prefix
14
Q
If the substituent group is: amine or an alcohol, then …
A
the parent group is classed as the functional group and benzene is classed as the prefix
15
Q
What is the prefix for benzene?
A
phenyl
16
Q
Draw Benzene carboxylic acid
A
google it or check notes
17
Q
Draw Benzaldehyde
A
google it or check notes
18
Q
Some molecules may contain more than one substituent group, so it may have ___ substituents bonded to it.
A
two
19
Q
We number the benzene ring like you would a ____ chain
A
carbon
20
Q
The substituent groups are listed in _____ order and using the ________ possible number.
A
alphabetical
smallest
21
Q
Draw 2-chloro methylbenzene
A
google it or check notes
22
Q
Draw 3-methylphenylamine
A
google it or check notes
23
Q
When was Benzene discovered? and by who?
A
Discovered in 1825 by Michael Faraday
24
Q
what is the percentage make up of benzene found by faraday? relative formula mass, and empirical formula
A
.92% carbon, 8% hydrogen
.It has a relative formula mass of 78
.Empirical formula found to be CH
25
What was weird about benzene when discovered?
.The structure was difficult to define
26
Who proposed the first structure of Benzene, what was it and did it work?
.Kekule’s proposed structure for benzene
.It was planar, cyclic with alternating double and single bonds which had 120’ bond angles
.But there were problems with this structure
27
What was the chemical evidence against Kekule's benzene?
.Benzene would not react with bromine, hydrogen bromide, and sulfuric acid
.This tells us there are no double bonds in the molecule
.The molecule does not undergo electrophilic addition reactions
28
What was the bond length evidence against Kekule's benzene?
.A carbon-carbon single bond length is 0.153nm
.A carbon-carbon double bond length is 0.134nm
.So you would expect benzene to be an irregular hexagon
.In 1922, Kathleen Lonsdale used x-ray diffraction to measure the bond length in benzene
.She found it had a regular shape
.She found that all the carbon-carbon bonds were the same length – 0.14nm
.Each bond is an intermediate between a single and double bond
29
What was the thermochemical evidence against Kekule's benzene?
.The enthalpy of hydrogenation is defined as the change in enthalpy when 1 mole of unsaturated compound reacts with an excess of hydrogen to become fully saturated
.The molecule had an enthalpy of -208, Kekule’s model in theory should have had -360
.So it’s bonds are more stable than cycloalkenes, as it is less exothermic than expected
30
Describe the declocalised model of benzene
.Each carbon atom has 3 σ (normal) bonds
.This leaves a spare electron in 2p orbital
.120’ bond angle between carbon atoms
.Planar hexagonal molecule
.2p orbitals overlap above and below the ring
.To form pi bonds
.The electrons in the pi bonds are delocalised
31
Draw the delocalised model of bezene
check notes or google
32
Draw Kekule's benzene model
Check notes or google
33
What is an electrophile?
An electrophile is an electron acceptor and can have a positive charge
34
What must an electrophile have to attack the stable benzene ring?
An electrophile has to have a strong positive charge to be able to attack the stable benzene ring, most compounds just aren’t polar enough
35
What does an electrophile need when attacking a benzene ring?
Needs a halogen carrier – iron, iron halides (e.g. FeCl3) or aluminium halides (e.g. AlCl3)
36
Br-Br: + AlBr3
AlBr4- + Br+
37
In an electrophilic substitution reaction with benzene, what does the halogen carrier do?
The halogen carrier accepts a lone pair of electrons from a halogen atom, as the lone pair is pulled away from the polarisation increases forming a strong electrophile
38
What is halogenation?
when a hydrogen atom is substituted for a halogen on a benzene ring
39
Give an example of halogenation
bromine is substituted onto a benzene ring to make bromobenzene
C6¬H6 + Br2 AlBr3 C6H5Br + HBr
40
WHat is the mechanism to a halogenation?
Step 1 – creating the electrophile with the halogen carrier catalyst
Step 2 – electrophile accepts a long pair of electrons from the benzene ring to form a dative covalent bond, this forms as unstable intermediate, the intermediate breaks down to form the organic product
Step 3 – the catalyst is regenerated
41
Draw the halogenation of benzene with Br2 with the AlBr3 catalyst
check notes or google
42
Benzene reacts with nitric acid at what speed?
slowly
43
How can we increase the rate of reaction of benzene and nitric acid?
by using sulphuric acid as a catalyst and 50’C
44
What happens when benzene reacts with nitric acid?
The H atom is substituted for a nitro (NO2) group
45
C6H6 + HNO3 H2SO4
C6H5NO2 + H2O
46
Draw the mechanism for benzene and nitric acid
check notes or google
47
Describe the steps of the mechanism for benzene and nitric acid
Step 1: Creating the electrophile with the sulphuric acid
Step 2: Electrophile accepts a lone pair of electrons from the benzene ring to form a dative covalent bond, this forms an unstable intermediate – the intermediate breaks down to form the organic product
Step 3: The catalyst is regenerated
48
Why is the reaction between benzene and nitric acid kept at 50’C?
so that only 1 nitro group attaches
49
What is alkylation?
.This is when a hydrogen atom is substituted for an alkyl group on a benzene ring
.Called the Friedel crafts reaction
50
In alkylation, what does the alkyl group need to be attached to?
a halogen
51
Give an example of alkylation
a methyl group is substituted onto a benzene ring to make methyl benzene
52
For alkylation, the halogen in the catalyst has to be what?
the same as the halogen the alkyl group is attached to
53
Draw the mechanism for attaching a methyl group to benzene
Check notes
54
What is Acylation?
.This is when a hydrogen atom is substituted for an acyl chloride group on a benzene ring
.Also called the Friedel crafts reaction
55
Draw the acyl chloride group?
check notes or google it
56
In an acylation reaction, Ethanoyl chloride reacts with benzene to make what?
phenylethanone
57
Draw the mechanism for benzene becoming phenylthanone
check notes
58
What are phenols?
Phenols are a type of organic chemical containing a hydroxyl group (-OH) functional group directly bonded to an aromatic ring
59
The simplest member of the phenols is ?
Phenol
60
Draw phenol
check notes or google
61
.Any compound that has an OH (hydroxyl) group bonded directly to a benzene ring is a what?
phenol
62
.If the compound doesn’t have a OH bond directly but still has an OH group it is classed as an ______, not a ______
alcohol, not a phenol
63
.Phenol is less soluble in water than alcohols, why?
due to its non-polar benzene ring
64
When dissolved in water, phenol partially dissociates to form what?
a phenoxide ion and a proton
65
As phenol only partially dissociates it is ______, other phenols also act as ________
a weak acid (pH4-6)
weak acids
66
.Ethanol doesn’t react with sodium hydroxide (strong ___) or sodium carbonate (weak ___)
base
base
67
Phenols and carboxylic acids will react with ____________________ (like aqueous sodium hydroxide)
solutions of strong bases
68
carboxylic acids are strong enough to react with a weak base like sodium carbonate, you would observe what?
a gas/bubbles
69
Draw the mechanism for phenol and sodium hydroxide
check notes or internet
70
Draw the mechanism for phenol and sodium
check notes or internet
71
Describe the bromination of phenols?
.Phenol reacts with aqueous solution of bromine (bromine water)
.A halogen carrier is not required and the reaction can be carried out at room temperature
72
Draw the mechanism of phenol and Br2
Check notes or internet
73
What does the bromination of phenol look like?
This reaction decolourises bromine water and forms a white precipitate
74
Why does phenol react more readily with bromine than benzene?
.One of the lone pairs of electrons on the p orbital of the O atom in the OH is partially delocalised into the ring
.This increases the electron density
.The electrophile becomes more polarised
75
Describe the nitration of phenol
.Phenol readily reacts with dilute nitric acid at room temperature
.It does not need halogen carrier
.Makes with 2-nitrophenol or 4-nitrophenol and water
76
Draw the nitration of phenol mechanism
check notes or internet
77
Many aromatic compounds can undergo a second substitution, what is this called?
a di-substitution
78
What is the directing effect?
The presence of substituted groups on a benzene ring will have an effect on the substitution of further groups – this is known as the directing effect
79
Substituted groups can be classified by the effect they have on the electron density of the ring, what are the classifications?
- Electron donating – increases the electron density
| - Withdrawing electrons – decrease electron density
80
What are electron donating substitition groups also known as, why?
.Side chains that increase electron density allow electrophiles to react faster than with benzene, so are ‘activating’ products
81
Give an example of an electron donating substitution group
.OH – O lone pair orbitals overlap with delocalised ring
| .NH2 – N lone pair orbitals overlap with delocalised ring
82
Where do electron donating groups promote substitution?
.They increase the electron density at positions 2, 4, and 6
.So electrophiles are more likely to react at these positions
.The group directs substitution to positions 2, 4, and 6
.2, 4-directing
.The weaker position at 3 and 5 are rarely substituted
83
What are electron withdrawing substitition groups also known as, why?
.Side chains that decrease electron density slow electrophile reactions compared to benzene, so are ‘deactivating’ groups
84
Give an example of an electron withdrawing substitution group
.NO2 – O is more electronegative, drawing electrons away from the delocalised ring
85
Where do electron withdrawing groups promote substitution?
.It withdraws electron density at position 2, 4, and 6 – meaning that electrophiles are unlikely to react at these positions
.The group directs substitutes to position 3
.3- directing
.The weaker positions at 2 and 4 are rarely substituted
86
Where does NH2 direct?
2, 4
87
Where does OH direct?
2, 4
88
Where does OR direct?
2, 4
89
Where does F, CL, Br, and I direct?
2, 4
90
Where does R direct?
2, 4
91
Where does NO2 direct?
3
92
Where does COOH direct?
3
93
Where does CHO direct?
3
94
Where does COOR direct?
3
95
What is R?
An alkyl group
96
In a carbonyl group, what are the charges on the atoms?
The carbon is delta +
| The oxygen is delta –
97
What is a carbonyl group?
C double bonded to O
98
What are aldehydes?
C=O group at the end of the carbon chain
99
How are aldehydes named?
start from the aldehyde end, suffix ‘-al’
100
What are ketones?
C=O group somewhere along the carbon chain, never at the end
101
How are ketones named?
C=O carbon should have lowest possible number
102
Primary alcohols will oxidise to what?
aldehydes and carboxylic acids
103
What is needed to oxidise primary alcohols? What will be seen?
An oxidising agent, acidified potassium dichromate K2Cr2O7/H+, needs heat, colour change if there is a reaction to green
104
Forming Aldehydes , how?
- Distillation
- Only from primary alcohol
- Product must be distilled off or it will oxidise further
- Reaction mixture contains excess alcohol
- Colour change from orange to green
- Forms water
105
Forming Carboxylic Acids , how?
- Reflux
- From primary alcohol
- Heated under reflux with excess of [O] – ensures reaction goes to completion
- Colour change from orange to green
- Doesn’t form water (unless from primary alcohol, but not if from aldehyde)
106
What is benzene called when it has a ketone group attached to carbon 1?
Phenyl ethanone
107
What is benzene called when it has an aldehyde group attached to carbon 1?
Phenyl methanal
108
Secondary alcohols will oxidise to what?
Ketones
109
Conditions for oxidation of secondary alcohols
an oxidising agent, acidified potassium dichromate
- Heated under reflux with excess of [O], ensures reaction goes to completion
- Colour change from orange to green
110
What do tertiary alcohols oxidise to?
Tertiary alcohols don’t oxidise at all
111
Draw the product of the oxidation of propan-2-ol
check notes
112
Conditions for reduction of aldehydes and ketones?
Reduction –
- Needs a reducing agent, NaBH4/H2O (sodium tetrahydridoborate)
- Contains BH4- ions which is a source of H- ions
• Need to warm it using water or ethanol as a solvent
113
What is a H- ion called?
A hydride ion
114
• Aldehydes and ketones can be reduced to their respective alcohols using what?
the reducing agent NaBH4
115
If reduced CH3CH2CHO, you would get what?
CH3CH2CH2OH
116
Reducing an aldehyde creates a what?
primary alcohol
117
Reducing a ketone creates a what?
Secondary alcohol
118
NaBH4 produces the nucleophile what?
H-
hydride ion
119
Draw the equation for the reduction of CH3CH2CHO
check notes
120
Draw the equation for the reduction of CH3CH2COCH2CH3
Check notes
121
Draw the mechanism for the reduction of CH3CH2CHO
check notes
122
Hydrogen cyanide can be added across the C=O bond of which two functional groups?
aldehydes and ketones
123
What is hydrogen cyanide?
HCN
| a colourless and extremely poisonous liquid that cannot be safely used in labs
124
How is HCN used in labs? Why?
- We use sodium cyanide and sulphuric acid to provide the hydrogen cyanide in the reactions
- This makes it safer to carry out in a lab but it is still very dangerous
125
Why is the reaction of carbonyl compounds with HCN useful?
The reaction is very useful as it is a way of increasing the length of the carbon chain
126
How to name hydroxy nitriles
- Need to include the carbon on the CN as part of the longest carbon chain
'nitrile' is the suffix
127
Draw the mechanism of the reduction of CH3CH2CH2CH2CHO
Check notes
128
Draw the mechanism of the reduction of CH3COCH3
check notes
129
Draw the equation for the reaction of CH3CH2CHO and HCN
Check notes
130
Draw the mechanism of the reaction of CH3CH2CHO and HCN
Check notes
131
Draw 2-hydroxybutanenitrile
check notes
132
What does tollens agent react with?
- Tollens’ reagent oxidises aldehydes to carboxylic acids but does not oxidise ketones
133
How to form tollens agent
- Tollens reagent = NaOH(aq) added to AgNO3 until a brown precipitate is formed, then add dilute NH3 until precipitate dissolves to form a colourless solution
134
What does a positive tollens agent test form
A silver mirror
135
WHat happens to silver ions in tollens test
- Silver ions are reduced:
| o Ag+(aq) + e- Ag(s¬)
136
Draw the general formula for tollens test
cHECK NOTES
137
WHat is used to test for carbonyl compounds?
2-4, dinitrophenylhydrazine (2, 4-DNP or brady’s reagent)
138
In the carbonyl compound test, how is brady's agent used?
Is dissolved in methanol and sulfuric acid
139
What colour does brady's agent turn?
- Reacts with carbonyl groups to form a bright orange precipitate
140
WHat does brady's agent react with?
- It only happens for compounds with a C=O bond, so aldehydes and ketones
- Doesn’t work for COOH or esters
141
WHat is the orange precipitate from Bradys agent?
- The orange precipitate is derivative of a carbonyl compound and can be used to identify an unknown compound with a carbonyl group
142
The method for identifying a carbonyl compound using bradys agent
1. You are given an unknown compound with a carbonyl group
2. Add 2,4-DNP to see an orange precipitate formed that is a derivative of the carbonyl group
3. Filter off the crystals using a Buchner funnel and water pump
This is an impure solid you need to have a pure solid, so we need to purify and then recrystallize
4. Dissolve the crystals in the smallest amount of hot solvent (ethanol) to purify and then put the test-tube in ice water to allow the pure solid to recrystallize
5. Filter off the crystals again using a Buchner funnel and water pump, this time you have a pure solid
6. Find the melting point of the pure solid
7. Compare to a known database of melting points for carbonyl derivatives to identify carbonyl
143
Descibr carboxylic acids
- A homologous series which contain the carboxyl functional group COOH
- The bonds are in a planar arrangement
- Include a carbonyl (C=O) group and a hydroxyl (O-H) group
144
How to name carboxylic acids
- Select the longest chain of C atoms containing the COOH group
- Remove the e and add oic acid after the basic name
- Number the chain starting from the end nearer the COOH group
- As in alkanes, prefix with alkyl substituents
- Side chain positions are based on the C in COOH being 1
145
Why are carboxylic acids soluble in water?
Carboxylic acids are polar molecules, electrons are drawn towards the oxygen atoms.
Hydrogen bonds form between the highly polarised hydrogen and oxygen atoms on the molecules.
This makes them soluble in water.
146
As the carbon chain gets longer, carboxylic acids get less soluble, why?
this happens as the non-polar carbon chain having a greater effect on the overall polarity.
147
Acid + Metal -->
Salt and hydrogen
148
Acid + Metal Oxide -->
Salt and water
149
Acid + Alkali -->
salt and water
150
Acid + Metal Carbonate -->
Salt and water and carbon dioxide
151
2HCl(aq) + 2Na(aq) -->
2NaCl(aq) + H2(g)
152
2HCl(aq) + Na2O(s) -->
2NaCl(aq) + H2O(l)
153
HCl(aq) + NaOH(aq) -->
NaCl(aq) + H2O(l)
154
2HCl(aq) + Na2CO3(s) -->
2NaCl(aq) + H2O(l) + CO2(g)
155
Carboxylic acids are ___ acids and take place in ____ reactions with metals and _______ reactions with bases (alkali’s, metal oxides and metal carbonates).
weak
redox
neutralisation
156
In some reactions of carboxylic acids what is formed?
carboxylate salts
157
What is a carboxylate salt?
One of the ions formed in the salt is a carboxylate ion.
158
CH3COOH
CH3COO- + H+
159
Ethanoic acid
Ethanoate ion + Hydrogen ion
160
Name and give the structure of the 3 first carboxylate ions
- Methanoate ion CHOO-
- Ethanoate ion CH3COO-
- Propanoate ion CH3CH¬2COO-
161
Benzene with a carboxylic acid group when ionised becomes what?
a Benzoate ion NOT a benzanoate ion
162
, Ethanoic acid + Sodium -->
Sodium ethanoate + Hydrogen
163
Ethanoic acid + sodium
sodium ethanoate + hydrogen
164
Ethanol + sodium
sodium ethoxide + hydrogen
165
Sodium ethanoate written structure
Na+CH3COO-
166
Sodium ethoxide writtren structure
C2H5O-Na+
167
A derivative of carboxylic acid is what?
a compound that can be hydrolysed to form the parent carboxylic acid it was formed form.
168
All carboxylic acid derivatives have a common sequence of atoms in their structure known as what?
an acyl group.
169
Draw an acyl group
CHECK NOTES OR GOOGLE
170
Draw an ester group
CHECK NOTES OR GOOGLE
171
Draw an acyl chloride group
CHECK NOTES OR GOOGLE
172
Draw an amide group
CHECK NOTES OR GOOGLE
173
Draw an acid anhydride group
CHECK NOTES OR GOOGLE
174
Draw
Ethanoic acid + methanol
CHeck NOTES OR GOOGLE
175
What is esterfication?
This is a reaction where an alcohol and a carboxylic acid react together to form an ester and water. It is a condensation reaction.
176
Reagents and conditions for esterfication?
Reagents: catalyst (concentration H2SO4)
Conditions: warm
177
Propanoic acid + ethanol
ethyl propanoate + water
178
What is special about esters?
Most esters have a pleasant odour.
| Depending on the alcohol and acid used, many different fragrances can be made.
179
What is an acid anhydride?
An acid anhydride is formed when water is removed from two molecules of carboxylic acid.
180
2 ethanoic acids form what when water is removed?
ethanoic anhydride
181
How can you make an ester using an alcohol?
You can form an ester using acid anhydride and an alcohol.
182
Acid anhydride + alcohol
ester + carboxylic acid
183
Ethanoic anhydride + methanol
methyl ethanoate + ethanoic acid
184
Draw ethanoic anhydride + methanol
check notes
185
What is hydrolysis?
Hydrolysis is the chemical breakdown of a compound in the presence of water or in aqueous solution
186
What are the two types of hydrolysis?
There are two types:
1. Acid hydrolysis
2. Alkaline hydrolysis
187
Describe the process of acid hydrolysis
- Heated under reflux with dilute aqueous acid
- Ester broken down by water using the acid as a catalyst
- Reversible reaction
188
Finish the equation
CH3COOCH3 + H2O HCl
CH3COOH + HOCH3
189
Describe the process of alkaline hydrolysis
- Reflux with aqueous alkali (NaOH or KOH)
- Get a carboxylate salt and alcohol
- Salt can be used to make soap – saponification
- Irreversible
190
Finish the equation
CH3COOCH3 + NaOH
CH3COONa + HOCH3
191
Draw an acyl group
check notes or google
192
Draw an acyl chloride
check notes or google
193
How to name an acyl chloride group
The primary suffix name is based on the longest carbon chain name (minus ‘e’) + ‘oyl chloride’ for the COCl
The carbon atoms are numbered from the C with the acyl functional group
194
Draw propanoyl chloride
check notes or google
195
Draw benzoyl chloride
check notes or google
196
Amines can be classified as primary, secondary, and tertiary, how is this determined?
This is determined by the number of carbon alkyl (carbon chain) or aryl (benzene ring) attached to the N atom.
197
Draw a primary amine
check notes or google
198
Draw a secondary amine
check notes or google
199
Draw a tertiary amine
check notes or google
200
How to name amines
If the amine (NH2) group is on the end of the carbon chain, the suffix is amine. You add the suffix to the alkyl group.
If the amine (NH2) group is on any other carbon chain except carbon 1, the prefix is amino. You need to give the position of the amine group.
In secondary and tertiary amines that contain the same alkyl group you have a prefix di or tri.
201
In secondary and tertiary amines that contain two or more different alkyl groups
The compound is named as an what?
N-substituted derivative
202
Draw N-methl propylamine
check notes
203
Draw N-ethyl N-methyl propylamine
check notes
204
Amides can be classified as primary, secondary, or tertiary, how is this determined?
This is determined by the number of carbon atoms attached to the N atom
205
Draw a primary, tertiary and secondary aminde (using R)
check notes
206
Formula of propanamide
CH3CH2CONH2
207
Formula of benzamide
C6H5CONH2
208
Formula of N-ethyl butanamide
CH3CH2CH2CONHCH2CH3
209
Formula of N, N-dimethyl methanamide
CHON(CH3)CH3
210
How are acyl chlorides made?
by reacting a carboxylic acid with thionyl chloride (SOCl2)
211
CH3CH2COOH + SOCl2
CH3CH2COCl + SO2 + HCl
212
What would you see if HCl is produced as a product in carbonyl reactions?
Steamy white fumes
213
Describe the reaction of acyl chloride and alcohols
With Alcohols to Form Esters
| This is a vigorous reaction which happens at room temperature.
214
Propanoyl chloride + propan-1-ol
propyl propanoate + HCl
215
Describe the reaction of acyl chloride and phenol
With phenol to form an aromatic ester
Esters are formed again during the esterification reaction between phenol and an acyl chloride
Phenol + acyl chloride ester + HCl
216
Phenol + propanoyl chloride
phenyl propanoate + hydrogen chloride
217
Describe the reaction of acyl chloride and water
With water to form carboxylic acid
| This is a vigorous reaction with cold water
218
Propanoyl chloride + water
propanoic acid + hydrogen chloride
219
Describe the reaction of acyl chloride and ammonia
With ammonia to form amides
| This is a violent reaction at room temperature to form a primary amide
220
Propanoyl chloride + ammonia
propenamide + ammonium chloride
221
Describe the reaction of acyl chloride and amines
With amines to form amides
| This is a violent reaction at room temperature to form secondary amides
222
Propanoyl chloride + methylamine
N-methylpropanamide + methylammonium chloride
223
Ester 1 ( C6H5COHCOOC(CH3)2 ) is less soluble than mandelic acid ( C6H5CH(OH)COOH ), why?
Hydrogen bonds are formed with water, between oxygen and hydrogen, mandelic acid has 2 OH groups (whilst ester 1 has 1), therefore more hydrogen bonds can be formed and so it is more soluble
224
Define acid
Acid – In water, an acid releases hydrogen ions (H+) into solution
225
Define base
Base – A base is a compound that neutralizes an acid, by accepting a hydrogen ion, to form a salt
226
Define salt
Salt – A salt is the product of a reaction in which the H+ ions from the acid are replaced by the metal or ammonium ions
227
HCl + OH-
H2O + Cl-
228
Bases donates _ electrons to the hydrogen ion to form a ___ ___ bond, bases can either have a ___ ___ or a ____ ___.
2
dative covalent
lone pair
negative charge
229
How is ammonia a base?
Ammonia (NH3) is a base, it accepts a proton to become an ammonium ion.
230
NH3 + HCl
NH4Cl
231
Amines behave as ___ in chemical reactions
bases
232
How do amines behave as bases in chemical reactions?
The lone pair of electrons on the nitrogen accepts a proton (a hydrogen ion)
A dative covalent bond is formed, they form an ammonium ion
233
Ethylamine + H+
Ethylammonium ion
234
CH3CH2NH2 + H+
CH3CH2NH3+
235
Ethylamine + HCl
Ethylammonium chloride
236
CH3CH2NH2 + HCl
CH3CH2NH3Cl
237
The strength of a base depends on how available the nitrogen’s lone pairs of electrons is, how?
A lone pair of electrons are more available if its electron density is higher
The higher density, the more available the lone pair, the stronger the base
238
How strong of a base are aromatic amines? Why?
For aromatic amines, the benzene ring pulls the electrons towards the delocalized ring, electron density increases, weak base
239
How strong of a base is ammonia? Why?
For ammonia, it doesn’t have an aromatic group to pull the lone pair away or an alkyl group to push the lone pair of electrons forward, base
240
How strong of a base are aliphatic amines? Why?
For aliphatic amines (RNH2), the alkyl group pushes the electrons forward, towards the nitrogen, so the electron density increases, and the lone pair is more available, strong base
241
How to form primary aliphatic amines?
1. Ammonia has a lone pair of electrons on the N atom which allows it to act as a nucleophile in a reaction with a haloalkane, the product of this reaction is an ammonium salt
2. Aqeous alkali (NaOH) is added to generate the amine from the salt
242
Conditions for formation of primary aliphatic amines
For this reaction to happen, the conditions needed are:
- Excess NH3
- Ethanol as a solvent to prevent substitution of the haloalkane by water to make an alcohol – also called ethanolic ammonia
243
What are the equations for the formation of ethylamine, using 1-chloroethane?
CH3CH2Cl + NH3 CH3CH2NH3+Cl-
1-chloroethane + ammonia ethylammonium chloride
CH3CH2NH3+Cl- + NaOH CH3CH2NH2 + NaCl + H2O
Ethylammonium chloride + sodium hydroxide ethylamine + sodium chloride + water
244
How are secondary aliphatic amines formed?
The primary amine can react with the haloalkane to make a secondary amine.
245
What are the equations for the formation of di-ethyl amine, using 1-chloroethane and ethylamine?
This is a two stage reaction:
1. CH3CH2NH2 + CH3CH2Cl (CH3CH2)2NH2+Cl-
Ethyl amine + 1-chloroethane Di-ethyl ammoniumchloride
2. (CH3CH2)2NH2+Cl- + NaOH (CH3CH2)2NH + NaCl + H2O
Di-ethyl ammoniumchloride + sodium hydroxide Di-ethyl amine + sodium chloride + water
246
The secondary amine can react with the haloalkane to make a tertiary amine, what is the two step reaction for this? Using 1. (CH3CH2)2NH + CH3CH2Cl
1. (CH3CH2)2NH + CH3CH2Cl (CH3CH2)3NH+Cl-
Secondary amine + haloalkane salt (triethyl ammonium chloride)
2. (CH3CH2)3NH+Cl- + NaOH (CH3CH2)3N + H2O + NaCl
Salt + sodium hydroxide tertiary amine + water + sodium chloride
247
Draw the mechanism for CH3Cl + CH3CH2NH2
CHECK NOTES
248
Phenylamine is made by the reduction of _____
nitrobenzene
249
C6H5NO2 _____ C6H5NH2
reduction with concentrated HCl and Sn in reflux
250
What is the two step reaction for the formation of phenylamine from nitrobenzene?
1. C6H5NO2 + 7[H] C6H5NH3+Cl- + 2H2O
Nitrobenzene + reducing agent phenyl ammonium chloride (a salt) + water
2. C6H5NH3+Cl- + NaOH C6H5NH2 + NaCl + H2O
phenyl ammonium chloride (a salt) + sodium hydroxide phenylamine + sodium chloride + water
251
C6H5NO2 + 6[H]
C6H5NH2 + 2H2O
252
What are aminos?
Amino are organic compounds containing amine and carboxylic acid functional groups, the side R chain is specific to each amino acid
253
Draw the general displayed formula for an amino acid
check notes
254
What is the general written formula for amino acids?
RCH(NH2)COOH
255
What are the three types of amino acids and how do they differ?
```
- Alpha-amino acids
o 2 carbons
- Beta-amino acid
o 3 carbons
- Gamma-amino acids
o 4 carbons
```
256
Write the formula for glycine and state its proper name
```
o HCH(NH2)COOH
o Proper name is 2-amino ethanoic acid
```
257
Write the formula for alanine and state its proper name
```
o H3CH(NH2)COOH
o Proper name is 2-amino propanoic acid
```
258
Write the formula for phenylalanine and state its proper name
```
o H5C6H2CCH(NH2)COOH
o 2-amino, 3-phenyl propanoic acid
```
259
How is an amino acid both a proton donor and acceptor?
Amino acids contain an acid group (COOH) and a base group (NH2)
The COOH is a proton donor, and the NH2 is a proton acceptor
260
As amion acids are both proton donors and acceptors, what can they do?
This means it can react with itself so the H+ ion from the COOH is donated to the NH2, this forms an ion called a zwitterion
261
What is the charge on a zwitterion?
0
262
Zwitterions only form at their specific isoelectric point, what is an isoelectric point?
pH at which an amino acid exists as a zwitterion
263
What is the isoelectric point affected by?
Different R groups
264
Draw the general formula for the formation of zwitterions
check notes
265
Alanine’s isoelectric point is ?
pH 6.01
266
Draw the formation of alanine's zwitterion
check notes
267
What happens to zwitterions in acidic conditions?
a lower pH, it is in acidic conditions, and so H+ ions are added wherever they can be
268
What happens to zwitterions in basic conditions?
At pH 7.01, a higher pH, it is in alkaline conditions, and so H+ ions are removed wherever they can be
269
Draw the product of an alanine zwitterion in acidic conditions
check notes
270
Draw the product of an alanine zwitterion in basic conditions
check notes
271
What is glutamic acid's isoelectric point?
3.22 pH
272
Draw the product of an glutamic acids zwitterion in basic conditions
Check notes
273
Draw the product of an glutamic acids zwitterion in acidic conditions
Check notes
274
What is lysine's isoelectric point?
9.59pH
275
Draw the product of an lysine's zwitterion in acidic conditions
Check notes
276
Draw the product of an lysineds zwitterion in basic conditions
check notes
277
What's the equation for alanine (R=CH3) and HCL?
H3CCH(NH2)COOH + HCl CH3CH(N+H3)COOH Cl-
278
What's the equation for alanine (R=CH3) and NaOH?
CH3CH(NH2)COOH + NaOH CH3CH(NH2)COO-Na+ + H2O
279
What's the equation for alanine (R=CH3) and methanol?
CH3CH(NH2)COOH + CH3OH CH3CH(NH2)COOCH3 + H2O
280
WHat are stereoisomers?
Stereoisomers are species with the same structure but a different arrangement of atoms in space
281
WHich one of E-but-2-ene, and Z-but-2-ene is trans?
E-but-2-ene
282
What is superimpose?
to place or lie over another and they are the same
283
What does it mean if you can or cannot superimpose two molecules of the same structure?
If you can superimpose, they are identical, and cannot form an optical isomer
If you cannot superimpose, they are not identical, and can form an optical isomer
284
When you have 4 different groups attached to a carbon, the molecule shows what?
optical isomerism
285
WHat are chiral centres?
Carbon atoms with 4 different groups attached are called chiral centers
286
Where does the word chiral come from?
Chiral is the Greek word for hands
287
Draw 2-bromobutane and identify the chiral centre
check notes
288
Draw 2, 3-dimethyl pentane and identify the chiral centre
check notes
289
Draw chloroethanoic acid and identify the chiral centre
check notes (there is no chiral centre)
290
How to draw optical isomerism?
- Put chiral carbon in middle and draw groups off of it
- Use wedges, dashes, and lines as usual
- Draw it like a tetrahedron
- Mirror it
291
For a substance that can undergo optical isomerism, the different optical isomers are called what?
enantiomers
292
What is a racemic mixture?
A racemic mixture is when you have a mixture of a substances enantiomers together.
293
Draw the optical isomerism of CH3 C (OH) Cl
check notes
294
If a molecule has 1 chiral center, there will be _ isomers.
2
295
If a molecule has 2 chiral centers, there will be _ isomers.
4
296
For every chiral center, there are ___ possible isomers.
two
297
Draw the isomers of CH3 C (Cl) C (OH) Br
CHECK NOTES
298
What is a condensatio reaction?
A condensation reaction is when small molecules join to form a larger molecule with a loss of another small molecule – usually H2O or HCl
299
What are some examples of condensatio reactions?
```
- H2O
o Carboxylic acid and alcohol
o Carboxylic acid and amine
- HCl
o Acyl chloride and alcohol
o Acyl chloride and amine
```
300
What are the two important condensation polymers made on a large scale?
Polyesters and polyamides
301
What are common starting materials for condensation polymers?
carboxylic acids
302
What is condensation polymerisation?
- Condensation polymerization is when monomers join together to form a polymer with a loss of another small molecule – usually H2O or HCl
303
How are polyesters formed?
- To make a polyester – monomers are joined together by ester linkages to form a long chain (polymer)
- There are two ways of linking them
- From one monomer
o Must contain a COOH and a OH group
- From two monomers
o Must contain two COOH groups and the other contains two OH groups
304
Draw the monomer, polymer (3 units), repeat unity, and overall equation for poly(glygolic acid), HOCH2COOH
check notes
305
In condensation polyesters, what do the monomers have to be?
- One monomer has to be a diol (two OH groups)
| - One monomer has to be a dicarboxylic acid (two COOH groups)
306
Draw the monomers, polymer, repeat unit, and overall equation for the polyester of Benzene 1, 4 dicarboxylic acid, and ethan 1,2-diol
check notes
307
How to form a poly amide
To make a polyamide, monomers are joined by amide linkages to form a long chain (polymer)
There are two ways of linking them:
1. From one monomer
a. Must contain a COOH and an NH2 group (also be formed from an acyl chloride and an amine group)
2. From two monomers
a. One contains two COOH groups (or acyl chloride) and the other contains two NH¬2 groups
308
What can undergo condensation reactions as they have both a COOH group and an NH2 group?
amino acids
309
Alanine CH3CH(NH2)COOH, monomer, polymer, repeat unit and overall equaiton
check notes
310
What do you need for a di monomer polyamide?
- One monomer has to be a diamine (two NH2 groups)
| - One monomer has to be a dicarboxylic acid (two COOH groups) or diacyl group
311
- Condensation polymers can be reversed by hydrolyzing with water, but this is slow, so what is added?
- Condensation polymers can be reversed by hydrolyzing with water
- It would take a long time with water alone so an acid or base is added
312
Which hydrolysis do polyesters and polyamides prefer?
- Polyesters prefer hydrolysis with a base
| - Polyamides prefer hydrolysis with an acid
313
Draw the acid hydrolysis of COC6H6CO OCH2CH2CH2O
Check notes
314
Draw the alkali hydrolysis of COC6H6CO OCH2CH2CH2O
check notes
315
What is formed in alkaline hydrolysis of polyesters and polyamides?
dicarboxyate salt
316
Draw the alkali hydrolysis of COC6H6CO NHC6H6NH
Check notes
317
Draw the acid hydrolysis of COC6H6CO NHC6H6NH
Check notes
318
Why are reactions that form carbon-carbon bonds important?
Reactions that form carbon to carbon bonds are important in chemistry as it is a way of making new compounds with more carbon atoms.
319
What are the two ways of forming nitriles?
There are two ways:
1. From aldehydes and ketones
2. From haloalkanes
320
Haloalkana and NaCN equation, name type of reaction, and mechanism
CHECK NOTES
321
We can use nitriles as intermediates to help us create other organic substances, what can be made and what are the steps used?
We can make:
1. Amines
2. Carboxylic acids
We use reduction and hydrolysis reactions to create them.
322
Reduction of nitriles, product, reagents, equation with propananitrile as organic reagent
- Forms amines
- Reagents are:
o H2
o Nickel Catalyst
CH3CH2CN + 2H2 --> Ni --> CH3CH2CH2NH2
323
Hydrolysis of nitriles, product, reagents, equation with propananitrile as organic reagent
- Forms carboxylic acids
- Reagents are:
o Heat
o Dilute aqueous acid (usually HCl)
CH3CH2CN + 2H2O + HCl --> CH3CH2COOH + NH4+Cl-
324
What is oil of wintergreen?
Starting reagent for formation of aspirin, IUPAC name of Methyl-2-hydroxybenzoate and check notes for displayed formula
325
How to synthesise aspirin from oil of wintergreen
Stage 1 – Preparing the Organic Substances –
- 2-hydroxybenzoic acid would need to be prepared from oil of wintergreen
- Add NaOH
- This would be done under reflux
- After 30 minutes, leave the mixture to cool
- Add hydrochloric acid to neutralise the mixture
Stage 2 – Preparing the Aspirin –
- React the 2-hydroxybenzoic acid (salicylic acid) with ethanoic anhydride
- Add drops of concentrated acid
- Warm the mixture in a water bath until the solid dissolves
- Cool the mixture
- Filter under reduced pressure using the Buchner apparatus
- Slowly add the minimum amount of hot solvent (ethanol) into the impure aspirin
- The sample will dissolve
- Cool the mixture to allow recrystallisation
- Filter under reduced pressure using the Buchner apparatus
- Wash the purified aspirin in cold water (as aspirin is not very soluble in cold water)
- Place a small sample of aspirin in a melting point tube
- Use melting point apparatus – set to 130’C
- Insert sample into melting point apparatus
- Slowly increase the temperature, record the range over when it starts to melt
- Impurities lower the melting point and widen the range
326
Explain how a time of flight spectrometer works
1. injection
2. vaporization
3. ionisation chamber
4. acceleration area
5. drift region
6. detector
327
Describe and explain fragments in mass spectrometry
- Excess energy from the ionization process can be transferred to the molecular ion and cause it to split (fragment)
- When it fragments:
o It produces a smaller positive ion and radical
o The smaller positive ion is detected
o Fragment ions can be broken down further still
328
What does a CH bond do when it absorbs IR?
stretches
329
What does a HCH bond do when it absorbs IR?
bends
330
Each bond in IR spectroscopy vibrates with a unique freuquency, which is picked up by what?
the spectrometer
331
What does vibration in IR spectroscopy depend on?
- Bond strength
- Bond length
- Mass of the bonded atom
332
What are the types of movement found in IR spectroscopy?
- Symmetrical stretching
- Antisymmetrical stretching
- Scissoring
- Rocking
- Wagging
- Twisting
333
How to identify alcohols with IR spectorscopy?
Primary alcohol = 1050
Secondary alcohol = 1100
Tertiary alcohols = 1150
OH bond = 3200-3640
334
Mr of CH3+
15
335
Mr of C2H5+
29
336
Mr of C3H7+
43
337
Mr of OH+
17
338
Mr of C4H9+
57
339
Equation of formation of C6H14+ in hexane mass spectrometry
C6H14 C6H14+ + e-
340
Equation of formation of C4H9+ in hexane mass spectrometry
C6H14+ C4H9+ + •C2H5
341
How to check for polarity on a molecule?
Ask the two questions:
Are the surrounding atoms the same?
Is there a long pair on the central atom?
If the answer is yes to both its polar, if its no to both its polar, if its yes to one and no to the other its non-polar
342
Rf =
distance of pigment / solvent front
343
What does the Rf value tell you?
Generally if the Rf values are the same, they are the same substance (there are exceptions)
344
Problems with Rf values
- Components can have similar Rf values
| - The unknown substance is new and there is no previous chemical to compare it with
345
What is Thin Layer Chromatography (TLC)?
- TLC is very similar to paper chromatography
- Rather than using chromatography/filter paper the stationary phase is a thin uniform layer (usually silica gel) coated on a piece of plastic, metal, or glass
- The mobile phase is a liquid which acts as a solvent for the substances you are trying to separate or analyze
346
Steps of TLC
1. A base line is drawn in pencil across the plate and dots of the substances are placed along the line
2. The plate is placed in a beaker of the solvent such that the level of the solvent is below the line and the solvent moves up the plate
3. A lid is placed to ensure the atmosphere in the tank is saturated with the often volatile solvent which climbs up the plate causing the mixture to separate
4. As the solvent front moves up the plate the mixture separates into its different components
5. The solvent reaches near to the top of the plate and the plate is removed
6. The solvent front is noted and the solvent is left to evaporate
347
What happens if the substances are colorless in TLC?
- Using UV Light
o The stationary phase has a chemical added to it which will fluorescence under UV light, the spots need to be circled while under the light
- Chemically
o The chromatogram is dried and sprayed with a ninhydrin spray, amino acids react and turn a purple/brown colour
o You can also use iodine crystals, the chromatogram is dried and placed in an enclosed container with a few iodine crystals, the iodine vapor in the container may either react with the pots on the chromatogram, or simply stick more to the spots than to the rest of the plate, either way the substances you are interested in may show up as brownish spots
348
How does TLC work?
- Silica gel is a form of silicon dioxide (silica)
- The silicon atoms are joined via oxygen atoms in a giant covalent structure
- However, at the surface of the silica gel, the silicon atoms are attached to -OH groups
- The surface of the silica gel is very polar and, because of the -OH groups, can form hydrogen bonds with suitable compounds around it as well as van der waals dispersion forces and dipole-dipole attractions
- With a solid stationary phase, the pigments are adsorbed onto the surface of the solid particles or fibers
- The relative forces of attraction between the stationary phase, the mobile phase, and the pigment mean that separation happens
349
Define adsorption
Adsorption – is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface
350
Which pigments will move how much in TLC?
```
- Insoluble pigment
o Won’t move
- Strong forces of adsorption
o More polar so won’t move a lot
- Weak forces of adsorption
o Less polar so will move a lot
```
351
When will the Rf value stay the same?
- Providing the temperature, stationery phase, and solvent stay the same, the Rf value will stay the same on repeats
352
What is Gas liquid chromatography?
- In GLC a long column is often filled with a liquid compound
- In thinner tubes, the stationary phase is coated to the inside surface of the tube
- The sample is vaporized and pushed through the column by an inert carrier gas (most often nitrogen or helium)
353
How does gas-liquid chromatography (GLC) work?
- Depending on the solubility of the different compounds in the stationary liquid phase, their boiling points and the temperature of the column, the different compounds will travel through the GLC column at different speeds
- The length of time a compound remains in the column is known as the retention time
- It is calculated from the time the sample is injected until the maximum peak heigh for that compound is observed on the display/chromatogram
- Compare to a known database to find the molecule
354
Explain how to find the proportion of components in GLC?
The area under the peaks can be used to calculate the composition of the mixture
Area of triangle = ½ x base x height
Work out individual areas and add them together
Work out percentage of area taken up by each peak
