Organic Chemistry Flashcards
(444 cards)
1
Q
organic chemistry
A
the chemistry of carbon
2
Q
1C
A
meth
3
Q
2C
A
eth
4
Q
3C
A
prop
5
Q
4C
A
but
6
Q
5C
A
pent
7
Q
6C
A
hex
8
Q
7C
A
hept
9
Q
8C
A
oct
10
Q
9C
A
non
11
Q
10C
A
dec
12
Q
C bonds
A
4
13
Q
N bonds
A
3
14
Q
H bonds
A
1
15
Q
O bonds
A
2
16
Q
saturated compound
A
all the chemical bonds between carbons are single bonds
17
Q
unsaturated compound
A
at least one of the carbon to carbon bonds is a double or triple bond
18
Q
aliphatic compounds
A
contain open (straight or branched) chains of carbon atoms and closed rings of carbon with similar properties
19
Q
aromatic compounds
A
contain at least one benzene ring
20
Q
functional group
A
a group of atoms which are present in all members of any series, which determines
21
Q
homologous series
A
a group of organic compounds with a common functional group and successive members of the series differ in size by CH2
22
Q
structural isomerism
A
compounds with the same molecular formula but have differnt structural formula
23
Q
mirror images
A
not isomers
24
Q
molecules that can be easily straightened
A
not isomers
25
addition reactions
a molecule has extra atoms added without losing any of its own atoms
26
substitution reactions
atoms already on a molecule are substituted or replaced by different atoms
27
hydrocarbons
only has hydrogen and carbon
28
nomenclature
system of naming
29
longest chain for alkanes
just the longest carbon chain
30
longest chain for non alkanes
longest carbon chain containing the functional group
31
which way to number for alkanes
keep the carbons carrying a substituent as low as possible
32
which way to number non-alkanes
carbons in functional group kept as low as possible
33
2 of the same substituent
di
34
3 of the same substituent
tri
35
4 of the same substituent
tetra
36
order to list different substituents
alphabetical
| eg. 4-chloro-3-ethyl-3-methylheptane
37
numbers separted from numbers with a
,
38
numbers separated from letters by
-
39
rule 5 for alkene and alkynes only
position of double or triple bond indicated by lower of 2 numbers eg. pent-2-ene
40
what is boiling point an indication of?
how difficult it is to separate molecules from each other
41
are hydrocarbons polar or non-polar
non-polar
42
solubility of hydrocarbons
don't dissolve in non-polar solvents such as water but do in non-polar eg.cyclohexane
43
solubility rule
like dissolves like
44
boiling points of hydrocarbons
weak van der waal forces, low boiling points
45
Mr of hydrocarbons increases
greater the boiling point
46
small hydrocarbons at room temp
gases
47
large hydrocarbons at room temp
liquids
48
aldehydes and ketones contain what?
carbonyl group
49
carbonyl group
\
C = O
/
50
boiling points of aldehydes and ketones and why
higher than hydrocarbons , dipole dipole attraction vs van der waal
51
solubility of aldehydes and ketones and why
both soluble in water, both have polar ends which are attracted to water by hydrogen bonding
52
if the aldehydes and ketones have long C-H chains
the nonpolar ends become bigger and more important
large nonpolar end repels water more than the smaller polar end attracts the water so that the larger aldehydes and ketones are insoluble in water
53
functional group of alcohols
hydroxyl group
54
hydroxyl group
-O-H-
55
boiling points of alcohols and why
higher than comparable aldehydes and ketones because of hydrogen bonding
56
comparable
same Mr
57
solubility of alcohols and why
very soluble in water, hydrogen bonding
58
alcohols with large C-H chains
C-H becomes the bigger part, overall molecule gets bigger and non-polar part is now more important than polar. dissolves in cyclohexane and not water
59
carboxylic acids functional group
carboxylic group
60
carboxylic group
```
O
//
- C
\
O - H
```
61
boiling points of carboxylic acids and why
highest of all, hydrogen bonding and more sites for hydrogen bonding
62
summary of boiling points
Carboxylic acids, alcohols, aldehydes and ketones, hydrocarbons (alkanes, alkenes, alkynes)
double H bond, h bond, dipole dipole, van der waal
63
solubility of carboxylic acids and why
very soluble in water because they undergo hydrogen bonding
64
when C-H chain gets too long in carboxylic acids
non-polar part more important, dissolves in cyclohexane not water
65
crude oil
mixture of substances of different Mr
66
what is refining about
separating the substances from each other
67
fractional distillation
the heating of crude oil and then separating the various mixtures on the basis of their different boiling points
68
crude oil is
viscous
69
crude oil first goes into
a furnace
70
what goes in the bottom of the steel column
super heated steam
71
what comes out the bottom of the steel column
residue of tar
72
what happens in the furnace
it is partially vapourised
73
bottom of steel column
very hot
74
top of steel column
coolest part
75
interior of steel column arranged
in horizontal trays
76
X's tray
X can be removed
77
above X tray
X is liquid and falls down
78
below X tray
X is gas under pressure and floats up
79
4 types of petroleum gas
methane
ethane
propane
butane
80
-CH3
methyl
81
-C2H5
ethyl
82
-C3H7
propyl
83
-C4H9
butyl
84
2 uses of petroleum gas
domestic bottle gas and LPG
85
LPG
liquid petroleum gas used in some cars
86
light gasoline aka
petrol
87
carbon atoms per molecule of petrol
5-10
88
use of petrol
for fuel
89
petrol is mostly
alkanes
90
carbon atoms per molecule of naptha
7-10
91
carbon atoms per molecule of something you can use to make petrol
5-10
92
2 uses of naphtha
petrol and raw materials
93
4 things naphtha is used as a raw material for
plastics, solvents, fibres, detergents etc
94
carbon atoms per molecule of kerosene
11-14
95
2 uses of kerosene
jet engine fuel
| home heating
96
gas oil aka
diesel
97
carbon atoms per molecule of diesel
14-20
98
use of diesel
in diesel engines
99
carbon atoms per molecule of lubricating oil
20-30
100
use of lubricating oils
lubricating oil
101
lubricating oils are
viscous
102
why aren't lubricating oils used as fuel
not easily vapourised
103
carbon atoms per molecule of fuel oil
30-35
104
use of fuel oil
can be made into droplets and used as ship and power station fuel
105
carbon atoms per molecule of bitumen
>35
106
use of bitumen
road tar
107
smell of methane ethane etc.
odourless but sulphur containing mercaptans added to give a strong smells so leaks easily detected
108
smell of methane ethane etc.
odourless but sulphur containing mercaptans added to give a strong smells so leaks easily detected
109
petrol coming from fractioning column
inefficient fuel
110
what is an inefficient fuel
explodes on compression before spark ignites it
111
explodes on compression before spark ignites it
auto-ignition
112
auto-ignition causes
knocking
113
knocking causes 3
loss of power
engine damage
excessive noise in the car
114
what causes knocking
straight chain molecules
115
what prevents knocking
the presence of branched chain molecules
116
octane rating
the capacity of petrol to burn smoothly
117
octane rating scale
1-100
118
0 on octane rating
heptane
119
100 on octane rating
2,4,4 trimethylpentane
120
2,4,4 trimethylpentane aka
iso octane
121
definition of octane number of a fuel
the measure of the tendancy of a fuel to resist knocking
122
octane number of 97 efficiency
same as 97% 2,4,4 trimethylpentane and 3% heptane
123
2,4,4 trimethylpentane and heptane
reference substances
124
4 features of high octane rating fuel
- highly branched molecules
- short alkanes
- cyclical compound
- aromatic molecules
125
1 highly branched molecule
2,4,4 trimethylpentane
126
1 short alkane
pentane
127
1 cyclical compound
cyclohexane `
128
aromatic molecules
contain benzene
129
what was put into petrol before
anti-knocking agent
| tetra ethyl lead
130
3 reasons why use of tetra ethyl lead was stopped
lead pollution in air
it's tendency to poison catalytic convertors
toxicity to human health
131
4 ways to ensure petrol has a high octane number
isomerisation
reforming
adding oxygenates
catalytic cracking
132
isomerisation
when straight pentane and hexane with low octane numbers are heated and passed over a catalyst. they break up at and reform at random to give a mixture of straight and branched versions (isomers)
133
reforming aka
dehydrocyclisation
134
reforming
use of catalysts to form ring compounds, converted to cycloalkanes such as cyclohexane
135
2 things happening in reforming
hydrogen is expelled
| aromatic compounds are formed
136
valuble hydrogen made in dehydrocyclisation
piped away
137
adding oxygenates
3 oxygen containing compunds added to petrol to increase it's octane number
138
3 oxygen containing compunds that are added to petrol to increase it's octane number
methanol
ethanol
MTBE
139
MTBE
methyl tertiary butyl ether
140
secondary use of oxygenates
reduce the level of pollutants coming from petrol, especially CO2 gas
141
catalytic cracking aka
cat cracking
142
cat cracking definition
the breaking down of long chain hydrocarbon molecules using heat and catalysts into smaller molecules which are more useful
143
cat cracking is carried out on... and why
kerosine, diesel oil and fuel oil, to obtain shorter molecules of carbon length 5-10 and higher octane rating
144
2 things cat cracking yields
more molecules with carbons lengths 5-10
| smaller molecules such as alkenes
145
why are more molecules with carbons lengths 5-10 important
petrol can be manufactured
| usually highly branched ie. high octane number
146
why are smaller molecules such as alkenes important?
manufacture of plastics and other chemical products
147
use of cracking allows chemists to...
use of cracking allows chemists to convert many of the fractions from crude oil for which there is little use
148
h2 burns readily in O2, what are products?
only H2O
149
H2 + 1/2 O2 ->
H2O
150
ΔH =
-242 kj/mole
151
3 difficulties with hydrogen as a fuel
expensive to produce
very explosive in air
very low density
152
how is hydrogen produced
electrolysis or steam reforming of methane
153
steam reforming of methane
burning of fossil fuels
154
why is very low density a problem
difficult to store
| must be stored in high pressure containers
155
equation for steam reforming of methane to form H2
CH4 + H2O -> 3H2 +CO
156
equation for hydrogen gas being used in the industrial production of ammonia
N2 + 3H2 -> 2NH3
157
hydrogen also used in?
the hydrogenation of vegetable oils in margarine production
158
general formula of alkane
C2 H2n+2
159
functional group of alkanes
```
/
- C -
/
no double carbon bond
no triple carbon bond
no oxygen
```
160
name for alkanes
-ane
161
first alkane
methane
162
methane
CH4
163
ethane
c2H6
164
general formula of alkenes
CnH2n
165
functional group of alkenes
carbon to carbon double bond
166
first alkene
ethene
167
ethane
C2H4
168
general formula of alkynes
CnH2n-2
169
functional group of alkynes
carbon to carbon double bond
170
first alkyne
ethyne
171
ethyne
C2H2
172
alcohol general formula
CxHy-OH
173
functional group of alcohol
-O-H
174
first alcohol
methanol
175
methanol
CH3OH
176
general formula of aldehydes
CxHyCHO
177
functional group of aldehydes
```
O
//
-c
\
H
```
178
first aldehydes
methanal
179
methanal
HCHO
180
general formula of ketones
(CxHy)nCO
181
functional group of ketones
O
//
C
/ \
182
first ketone
propanone
183
propanone
(CH3)2 CO
184
general formula of carboxylic acids
CxHyCOOH
185
functional group of carboxylic acids
methanoic acid
186
methanoic acid
HCOOH
187
aromatic hydrocarbons contain what
a benzene ring
188
molecular formula for benzene
C6H6
189
who proposed the structural formula for benzene and when
kekule in 1865
190
was kekule correct?
no
191
first characteristic of benzene that proved kekule wrong?
| C-C length
he suggested that there were two different bond lengths but there is only one in benzene, all the bonds are equal
192
second characteristic of benzene that proved kekule wrong? C=C
kekule's structure had very reactive C=C bonds, which would suggest it undergo addition reactions
193
what can tell us that benzene does not have C=C bonds?
| 2
very unreactive, undergoes substitution reactions
| does not decolourise bromine water of KMnO4
194
how many valence or bonding electrons does carbon have
4 valence or bonding electrons
195
3 of carbon's valence electrons in benzene
involved in σ bonds with 2 neighbouring carbon atoms and one hydrogen atom
196
the 4th valence electron is benzene
exists in an unused p orbital
197
how many unused p orbitals in benzene
6
198
how are the 6 unused p orbitals aligned?
perpendicular to the plane of the ring
199
where are the 6 π bond electrons located?
they are free to move throughout the entire ring so they don't belong to any carbon
200
what does it mean that they are free to move throughout the entire ring so they don't belong to any carbon
they are delocalised
201
what does the fact that 6 electrons are delocalised give benzene?
extra stability
202
what does the extra stability account for?
it's general unreactivity
203
why should contact with benzene be avoided?
it's known to be carcinogenic
204
what is a safer molecule derived from benzene
methyl benzene
205
what is methyl benzene known for
its a non polar solvent. won't dissolve in water but will in cyclohexane
206
the look of a benzene molecule
a flat molecule
207
bond angle of carbons in benzene
120º
208
how are aromatic compounds obtained
mostly from the fraction distillation of crude oil
209
general formula of alkanes
C n H 2 n+2
210
alkanes, saturated or unsaturated?
saturated
211
all carbons in alkanes
have 4 single bonds out of them
212
structure of carbons in alkanes
tetrahedral structure
213
are alkanes reactive
mostly unreactive
214
what does the fact that alkanes are mostly unreactive explain
explains why they are widely found in nature
215
first four alkanes at room temperature
gases
216
next twelve alkanes at room temperature
liquids
217
heavier alkanes
waxy solids
218
where are the waxy solid, heavy alkanes found
in plants
219
first for alkane gases
methane, ethane, propane, butane
220
where are the first for alkanes produced
in large quantities in fractional distillation of crude oil
221
3 properties of the first 4 alkanes
light
colourless
odourless
222
why are the first 4 alkanes excellent fuels
they combust easily
223
are the first 4 alkanes reactive
generally unreactive
224
where can methane also be produced? 2
the anaerobic respiration of decaying organic matter and by farm animals
225
3 examples of decaying organic matter that produce methane
farm manure
marshes
rice paddy fields
226
2 uses of methane
a fuel
on an industrial scale, to make H2 gas
make NH3
227
how is H2 gas made out of methane
it is reacted with high pressure steam
228
production of NH3
first step in the manufacture of artificial nitrate fertiliser
229
methane is regarded as
a greenhouse gas that contributes to global warming
230
chloroalkanes
one or more of the hydrogen atoms in alkane molecules is replaced by a chlorine atom
231
are chloralkanes saturated or unsaturated
saturated
232
structure of chloroalkanes
tetrahedral structure
233
chloroalkanes at room temp
liquids
234
are chloroalkanes good solvents
excellent solvents
235
are chloroalkanes polar or non-polar
largely non polar
236
bp of chloroalkanes
low bp, vaporise off surfaces easily
237
2 uses of chloroalkanes
dry cleaning clothes
| tippex
238
what is dichloromethane found in
paint stripper
239
how does dichloromethane work as a paint stripper
acts as a solvent and dissolves old unwanted paint and that it evaporates due to us low boiling point, leaving the dry dissolved paint behind as a flaky surface, easily scraped off
240
recent concern about chloroalkanes
they cause harm to the ozone layer in the atmosphere `
241
if there are more than 3 carbons?
they can undergo isomerism
242
general formula for alkenes
CnH2n+2
243
functional group of alkenes
C=C
244
smallest alkene
ethene
245
alkenes, saturated or unsaturated
unsaturated
246
smallest 3 alkenes at rt
gases
247
other alkenes
liquids or soft solids
248
shape of alkene molecules
planar
249
why are alkenes planar
2 carbons joined by a double bond
250
shape of longer carbon chain alkenes e.g. pent-1-ene
has a planar end with the functional group and the other end is tetrahedral
251
are alkenes reactive
much more reactive than alkanes
252
why are alkenes much more reactive than alkanes
because the C=C bond is much less stable than the C-C and C-H bonds
253
double bond consists of
sigma and pi bonds
254
which is weaker sigma or pi
pi is weaker
255
why are C=C bonds more reactive than C-C bonds
the weak pi bond breaks easily releasing it's two bonding electrons to bond with other atoms or groups of atoms
256
in general, what do addition reactions cause
a change in structure from planar to tetrahedral
257
how do you prepare an alkene
dehydrate the appropriate alcohol
258
appropriate alcohol
same number of carbon
259
preparation of ethene formula
C2H5OH --> C2H4 + H2O
260
ethanol
C2H5OH
261
preparation of ethene, what holds the ethanol in place
glass wool
262
how is the tube placed in the preparation of ethene
horizontally
263
preparation of ethene, where do you clamp the boiling tube
near its neck
264
preparation of ethene, what do you add half way along the tube
aluminium oxide
265
preparation of ethene, how much aluminium oxide do you use
2g
266
preparation of ethene, how do you push the glass wool into the tube
using a glass rod
267
preparation of ethene, how do you put the aluminium oxide into the tube
using a spatula
268
preparation of ethene, how is ethene collected
by the downward displacement of water
269
preparation of ethene, describe how you heat the tube
just touch the flame onto the alcohol end
270
preparation of ethene, what happens when the alcohol vapour passes over the aluminium oxide?
its dehydrated
271
aluminium oxide
Al2O3
272
preparation of ethene, what do you do at the start when gas starts to come out and why?
let is bubble off for a minute do not collect as it is mostly air
273
preparation of ethene, how much do you collect
collect about 5 jars of ethene
274
preparation of ethene, after collecting each jar
put a stopper in
275
preparation of ethene, after collecting sufficient amount
turn off bunsen burner and immediately disconnect delivery tube to prevent suck back
276
preparation of ethene, how do you disconnect delivery tube
loosening the clamp and sliding up so that the delivery tube is out of the water
277
what is suck-back?
where a vacuum occurs in the tube as it cools and draws cold water into the hot boiling tube causing it to splinter and crack
278
2 tests for unsaturation
bromine water
| acidified potassium mangnate
279
colour change of bromine water
red/orange to colourless
280
colour change of acidified potassium magnate
purple to colourless
281
potassium magnate
KMnO4
282
reaction for production of ethene
elimination reaction
283
definition of an elimination reaction
a reaction in which a small molecule is removed from a large molecule leaving a double bond behind on the remaining larger molecule
284
colour of ethene
colourless
285
smell of ethene
sweet smell
286
solubility of ethene
insoluble in water, soluble in cyclohexane
287
how do you test ethene for unsaturation
add some bromine water, stopper an invert (or with acidified potassium magnate)
288
how do you combust a jar of ethene
apply a lighted wax taper to its mouth
289
combustion of ethene
burns brightly
290
what is produced when ethene is burned in air
CO2 is formed
291
testing burned ethene for CO2
put some lime water in it, stopper and invert. goes milky white
292
burned ethene turns into
water and carbon dioxide
293
burned ethene in air equation
C2H4 + 3O2 --> 2CO2 + 2H2O
294
general rule, organic compounds burn
to form CO2 and H2O
295
preparation of ethene 3 other precautions
do not let flame directly near ethanol
handle glass wool with gloves
tie back hair, wear goggles, wear a lab coat
296
why do alkenes undergo addition reactions
because they have a double bond which makes it easy to 'add on' items
297
why are alkanes much less reactive than alkenes or alkynes
they have no C=C bond or C=-C bond to enable addition reactions to occur
298
substitution reactions in alkanes
much slower to occur
299
2 catalysts for hydrogenation of ethene
200º and Ni
300
hydrogenation of ethene equation
C2H4 + H2 ---> H2H6
301
H2H6
ethane
302
Chlorination of ethene equations
C2H4 + Cl2 ---> C2H4Cl2
303
product from chlorination of ethene
1,2-Dichloroethane
304
bromination of ethene equation
C2H4 + Br2 --> C2H4Cl2
305
product of bromination of ethene
1,2-Dibromoethane
306
colour of bromine
red/yellow
307
colour of 1,2-Dibromoethane
colourless
308
why do you never use bromine in the bromination of ethene
it's too dangerous for the lab, you use bromine water
309
equation, adding hydrogen chloride to ethene
C2H4 + HCl ---> C2H4Cl
310
catalyst for adding hydrogen chloride to ethene
AlCl3
311
AlCl3
aluminium chloride
312
product of adding hydrogen chloride to ethene
1-chloroethane
313
hydration
addition of water
314
what is hydration of ethene the reverse of?
production of ethane from ethanol (dehydration of ethanol)
315
2 catalysts for the hydration of ethene
high temperature and pressure
316
equation of hydration of ethene
C2H4 + H2O --> C2H4OH
317
C2H4OH
ethanol
318
what does polymerisation do to one ethene
turns it into polyethene
319
what do you not do when drawing polymers
put Hs at the ends, they're not finished, they are repeating units
320
1 use of hydrogenation in industry
in the food industry, used to convert some double bonds in vegetable oils (polyunsaturates) to single bonds, changing them from liquid oils to spreadable semi-solids eg.margarine
321
3 double bonded oils
palm oil
sunflower oil
corn oil
322
2 saturated fats
dairy and cream
323
which are thought to be healthier, polyunsaturated fats or saturated fats ?
polyunsaturated fats
324
how can you make an oil as soft or hard as you want
by controlling the degree of hydrogenation
325
2 advantages of hydrogenation
healthier unsaturated fats are spreadable
| can make fats as soft or hard as required
326
the product of chlorination of ethene
1,2-Dichloroethane
327
where is 1,2-Dichloroethane used?
it is the raw material for the production of chloroethene
328
what is chloroethene
it is a well known monomer used for the production of polychloroethene
329
common name for chloroethene
vinyl chloride
330
common name for polychloroethene
poly vinyl chloride (PVC)
331
word equation for ethene -> PVC
ethene + chlorine -> dichloroethane
| loses HCl to make chloroethane. polymerised to become polychoroethene (PVC)
332
chemical equation for ethene -> PVC
C2H4 + Cl2 -> C2H4Cl2 -> C2H3Cl->
| (C2H3Cl)n
333
what is the function of 1,1,1-trichloroethane
allows 2 reactants to mix together freely. i.e a solvent
334
addition of bromine (bromination) is
a test for unsaturation
335
how to be sure of unsaturation after bromination test
do a second test with KMnO4
| potassium mangnate
336
when fruits ripen, what do they produce
ethene
337
where is ethene also produced and what's its function
produced artificially in ripening rooms to spped up ripening
338
why should ripening fruit never be beside flowers
the ethene produced will cause they flowers to ripen and fall off
339
definition of polymerisation
where many small molecules called monomers join together to give a long polymer
340
what is high density polythene
polythene where long chains line close to each other and have no branching
341
2 features of high density polythene
rigid and a high melting point
342
what is low density polythene
long chains have branching out of them so they cannot lie close together
343
1 feature of low density of polythene
lower melting point
344
addition polymerisation
where no tiny molecules are expelled during the process
345
condensation polymerisation
where tiny molecules are expelled during the process
346
polymer of ethene
polyethene (polythene)
347
uses of polyethene
hard and soft plastic depneding if it's high density or low density
348
polymer of propene
polypropene (polyproylene)
349
2 uses of polypropylene
tough plastic
- beer crates
- stacking chairs
350
thermoplastic vs thermosetting
thermoplastics can be reheated and remoulded many times, thermosetting plastic cannot
351
general formula of alkynes
CnH2n-2
352
functional group of alkynes
C≡C (carbon to carbon triple bond)
353
polymer of chloroethane
polychloroethane (PVC)
354
2 uses of polychloroethane
doors and windows
| raincoats
355
reactions that alkynes undergo
addition reactions
356
why do alkynes undergo additiion reactions
because weak pi bonds break easily
357
2 features of C≡C
strong
| highly reactive
358
smallest alkyne
ethyne
359
whene ethyne burned in a stream of O2
produces temperatures in excess of 3,000°
360
what is used for cutting equipment
oxyacetylene
361
describe how oxyacetylene cutting equipment works
2 separate tanks of ethyne and oxygen are connected through a single outlet and the mixture is burned on exit in a controlled flame to give really high burning temperatures
362
formula of benzoic acid
C2H5COOH
363
formula of phenol
C6H5OH
364
formula for nitrobenzene
C6H5NO2
365
formula for methyl benzene
C6H5CH3
366
formula for benzaldehyde
C6H5CHO
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how to draw any of the aromatic compounds
draw a circle inside a hexagon and the substituent sticking out of one corner of the hexagon
368
sub in benzoic acid
COOH
369
sub in phenol
OH
370
sub in methyl benzene
CH3
371
sub in nitrobenzene
NO2
372
sub in benzaldehyde
CHO
373
combustion of ethene formula
C2H4 + 3O2 --> 2CO2 + 2H2O
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by what action can you make ethyne
by the action of water on calcium dicarbide
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describe calcium dicarbide
a grey/ black solid
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formula for preparation of ethyne
CaC2 + 2H2O --> Ca(OH)2 + C2H2
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CaC2
calcium dicarbide
378
Ca(OH)2
calcium hydroxide
379
C2H2
ethyne
380
how does calcium hydroxide look
cloud white ppt
381
what does ethyne look like
colourless gas
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when ethyne burned in air
a lot of soot produced
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when ethyne burned in pure oxygen
no soot produced
384
preparation of ethyne, what is used to filter out the impurities from the gas
acidified copper sulphate solution
385
preparation of ethyne, 3 impurities trapped by acidified copper sulphate solution
H2S
NH3
PH3
386
PH3
phosphine
387
why do impurities arise from CaC2
it is not purchased pure, but contains impurities that turn into H2S, NH3, PH3 when reacted with water
388
preparation of ethyne, what gives the gas odour
the impurities
389
2 things that happen when a jar of C2H2 is burned
1. gives off great heat
| 2. causes a great amount of soot to be formed
390
what was carbide used for
carbide lamps were used years ago before the invention of batteries
391
how does a carbide lamp work
water drips slowly onto CaC2 and the C2H2 produced is lit and burns brightly
392
preparation of ethyne, what can be used to prove that CO2 was produced in the reaction
limewater turns milky
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formula for combustion of ethyne with oxygen
2C2H2 + 5O2 --> 4CO2 + 2H2O + heat
394
why is great heat released when ethyne is burned
high energy carbon to carbon triple bond is broken during combustion
395
ethene flame
bright yellow flame
396
ethyne flame
sooty flame
397
preparation of ethyne, name of flask the water drips into
buchner flask
398
preparation of ethyne, what does the water drip from
a tap funnel
399
preparation of ethyne, what apparatus is used to collect the gas
a glass tube and a beehive stand
400
preparation of ethyne, where does the calcium carbide go
into the buchner flask
401
preparation of ethyne, what do you use to transfer the calcium carbide into to buchner flask
a spatula
402
preparation of ethyne, why do you never touch the calcium carbide
the moisture on you hand might start the reaction
403
preparation of ethyne, how fast do you let water flow
only in drips
404
preparation of ethyne, what happens to the flask contents when the water starts to drip
becomes cloudy white
405
preparation of ethyne, what happens to the flask when gas starts to be produced
get very hot
406
preparation of ethyne, what should you do with the first few jars and why
discard them, they are most likely just air
407
preparation of ethyne, how many jars do you collect
about 4 or 5
408
how do you test for ethyne gas
light the jar contents, should burn with a pop
409
preparation of ethyne, how do you stop the production of gas
stop the flow of water
410
preparation of ethyne, why do you dismantle the apparatus and empty the contents before before testing the ethyne
because we will be using a lighted taper on one of the jars and ethyne forms an explosive mixture with air
411
preparation of ethyne, smell of ethyne if impurities get through
unpleasant smell
412
is ethyne soluble in water and how do we know
no
| collected by the downward displacement of water
413
where do you burn a jar of ethyne
in a fume cupboard only
414
what is the soot produced when during ethyne
carbon soot
415
3 characteristics of ethene flame
less sooty/clear, less bright, bluish flame
416
bromination test on ethyne
add a very small amount of bromine water into a test tube of ethyne gas, stopper and shake well (yellow/red -> colourless)
417
KMnO4 test on ethyne
same as bromine water. colour change purple -> colourless
418
3 precautions of preparation of ethyne
keep naked flames away from ethyne, don't touch calcium dicarbide , do all tests on ethyne in a fume cupboard
419
reaction mechanism
a step by step account of how a reaction occurs
420
what drives a substitution mechanism
driven by free radicals
421
substitution reaction aka
free radical substitution
422
free radical
a group of atoms, or a single atom which are very reactive due to having one unbounded electron
423
free radical substitution reaction, chemical equation
CH4 + Cl2 -> CH3Cl + HCl
424
3 stages of free radical substitution reaction,
initiation stage
propagation stage
termination stage
425
free radical substitution reaction, initiation stage
UV light is needed to start the reaction
426
photochemical reaction
depends on light
427
what can prove that our free radical substitution reaction is a photochemical reaction
it doesn't occur in the dark
428
free radical substitution reaction, what is the splitting of Cl2 into 2 free radicals Clº and Clº
homolytic fission
429
homolytic fission
when a chemical bond breaks and each of the pieces retains one of the originally bonded electrons
430
free radical substitution reaction, when and how does the propagation stage start
begins automatically when initiation stage is over
431
free radical substitution reaction, 2 different repeating reactions in propagation stage are driven by
2 free radicals:
| Clº and CH3º
432
free radical substitution reaction, propagation stage, reaction driven by Clº
Clº + CH4 -> CH3º + HCl
433
free radical substitution reaction, propagation stage, reaction driven by CH3º
CH3 + Cl2 -> CH3Cl + Clº
434
free radical substitution reaction, propagation stage continues in a
chain reaction
435
free radical substitution reaction, propagation stage continues until
when one of the reactants starts to get scarce
436
free radical substitution reaction, if Cl2 gets scarce reaction
CH3º + CH3º -> C2H6
437
free radical substitution reaction, if CH3 gets scarce
Clº + Clº -> Cl2
438
free radical substitution reaction, if both Cl2 and CH3 get scarce
CH3º + Clº -> CH3Cl
439
free radical substitution reaction, 3 proofs to show that the mechanism proposed is correct
Presence of traces of C2H6
addition of tetra methyl lead lead which decomposed into free radicals and speeds up the reaction
will not occur without UV light
440
chain reaction
a reaction, once started, can only be stopped when at least one of the reactants is completely used up
441
free radical substitution reaction another example
chlorination of ethane
442
free radical substitution reaction, 2 free radicals driving the chlorination of ethane
ethyl or CH3CH2
443
free radical substitution reaction no.2chlorination of ethane, what is formed in the termination stage rather than ethane
butane
444
free radical substitution reaction, 2 free radicals driving the chlorination of ethane, what can be used to speed up the reaction
tetra ethyl lead
