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4 Organic Chemistry Flashcards

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1
Q

what is a hydrocarbon

A

a compound made up of only hydrogens and carbons

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2
Q

what is crude oil

A

a mixture of different hydrocarbons

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3
Q

what is fuel

A

a substance that when it is burned it releases heat energy

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4
Q

how does fractional distillation work

A

Fractional distillation is carried out in a fractionating column which is very hot at the bottom and cool at the top
Crude oil enters the fractionating column and is heated so vapours rise
Vapours of hydrocarbons with very high boiling points will immediately condense into liquid at the higher temperatures lower down and are tapped off at the bottom of the column
Vapours of hydrocarbons with low boiling points will rise up the column and condense at the top to be tapped off
The different fractions condense at different heights according to their boiling points and are tapped off as liquids
The fractions containing smaller hydrocarbons are collected at the top of the fractionating column as gases
The fractions containing bigger hydrocarbons are collected at the lower sections of the fractionating column

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5
Q

what is a fraction

A

a group of similar length hydrocarbons

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6
Q

trend in colour, boiling point and viscosity of the fractions

A

boiling point and viscosity increase as the boiling point increases
colour gets darker as the boiling points increase

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7
Q

refinery gases

A

1-4 carbons
boiling point less then 25’c
fuel for home cooking

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8
Q

gasoline

A

4-12 carbons
boiling point between 40-100’c
fuel for cars

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9
Q

kerosene

A

12-16 carbons
boiling point between 150-240’c
fuel for aircrafts

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10
Q

diesel

A

14-18 carbons
boiling point between 220-300’c
fuel for trains

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11
Q

fuel oil

A

19-25 carbons
boiling point between 250-320’c
fuel for ships

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12
Q

bitumen

A

more than 70 carbons
boiling point more than 350’c
making roads

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13
Q

what is the empirical formula

A

the simplest possible ratio of the atoms in a molecule
For example: Hydrogen peroxide is H2O2 but the empirical formula is HO

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14
Q

what is the molecular formula

A

the actual number of atoms in a molecule

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15
Q

what is the general formula

A

A ratio of atoms in a family of compounds in terms of ‘n’ where n is a varying whole number
For example, the general formula of a molecule that belong to the alkane family is CnH2n+2

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16
Q

what is the structural formula

A

In a structural formulae enough information is shown to make the structure clear, but most of the actual covalent bonds are omitted
Only important bonds are always shown, such as double and triple bonds
Identical groups can be bracketed together
Side groups are also shown using brackets
Straight chain alkanes are shown as follows:

CH3CH2CH2CH2CH3 or CH3(CH2)3CH3

Displayed formula:
H H H H
I I I I
H-C-C-C-C-H
I I I I
H H I H
I
H-C-H
I
H

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17
Q

what is the displayed formula

A

how the molecule is drawn
H H H H
I I I I
H-C-C-C-C-H
I I I I
H H I H
I
H-C-H
I
H

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18
Q

what is a homologous series

A

a series or family of organic compounds that have similar features and chemical properties due to them having the same functional group

All members of a homologous series have:
The same general formula
Same functional group
Similar chemical properties
Gradation in their physical properties
The difference in the molecular formula between one member and the next is CH2

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19
Q

what is a functional group

A

A group of atoms bonded in a specific arrangement that influences the properties of the homologous series (what is attached to the carbon)

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20
Q

what is isomerism

A

compounds that have the same molecular formula but different displayed formulae

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21
Q

how to name compounds

A

first part of the name second part of the name
NAME Number of C atoms name functional group Family

meth.. 1 ..ane none alkane
eth.. 2 ..ene C = C double bond alkene
prop.. 3 ..anol -OH alcohol
but.. 4 ..anoic acid -C=O-O-H carboxylic acid
pent.. 5 ..amine -NH2 amine
hex.. 6 ..yl ..anoate -C=O-O- ester

When there is more than one carbon atom where a functional group can be located it is important to distinguish exactly which carbon the functional group is on
Each carbon is numbered and these numbers are used to describe where the functional group is
When 2 functional groups are present di- is used as a prefix to the second part of the name

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22
Q

how to classify reactions of organic compounds as substitution, addition and combustion

A

A substitution reaction takes place when one functional group is replaced by another
CH4 + Br2 → CH3Br + HBr

An addition reaction takes place when two or more molecules combine to form a larger molecule with no other products
C2H4 + Br2 → C2H4Br2

This is the scientific term for burning. In a combustion reaction, an organic substance reacts with oxygen to form carbon dioxide (or carbon monoxide if incomplete combustion) and water.

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23
Q

possible products of complete combustion of hydrocarbons with oxygen in air

A

Complete Combustion happens when there is enough oxygen available, producing carbon dioxide (CO2) and water (H2O)

eg CH4 + 2O2 -> CO2 + 2H2O

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24
Q

possible products of incomplete combustion of hydrocarbons with oxygen in air

A

Incomplete Combustion happens when there is not enough oxygen available, with possible products being carbon monoxide (CO), carbon (C, soot), carbon dioxide (CO2) and water (H2O)

eg ethane + oxygen -> carbon monoxide + water

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25
effects of carbon monoxide on the capacity of blood to carry oxygen
Carbon monoxide is a toxic and odourless gas which can cause dizziness, loss of consciousness and eventually death The CO binds well to haemoglobin which therefore cannot bind oxygen meaning less oxygen and CO2 can be transported to and from organs and working muscles
26
what do the high temperatures in car engines allow
the temperature goes high enough to allow and oxygen from the air and nitrogen to react, forming oxides of nitrogen (NO and NO2)
27
how does the combustion of some impurities in hydrocarbon fuels results in the formation of sulfur dioxide
Fossil fuels are often contaminated with small amounts of sulfur impurities When these contaminated fossil fuels are combusted, the sulfur in the fuels get oxidised to sulfur dioxide
28
how does sulfer dioxide and and oxides of nitrogen contribute to acid rain
The sulfur dioxide produced from the combustion of fossil fuels dissolves in rainwater droplets to form sulfuric acid 2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq) Sulfuric acid is one of the components of acid rain which has several damaging impacts on the environment Nitrogen dioxide produced from car engines reacts with rain water to form a mixture of nitrous and nitric acids, which contribute to acid rain: 2NO2 (g) + H2O (l) → HNO2 (aq) + HNO3 (aq)
29
process of catalytic cracking
Catalytic cracking involves heating the hydrocarbon molecules to around 600 – 700°C to vaporise them The vapours then pass over a hot powdered catalyst of aluminium oxide or silica This process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions The molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure
30
why is cracking necessary
Crude oils vary considerably in their composition and some need more refining than others Supply is how much of a particular fraction can be produced from refining the crude oil Demand is how much customers want to buy Generally, the demand for certain fractions outstrips the supply so this is why cracking is necessary to convert surplus unwanted fractions into more useful ones This is mostly larger, heavier fractions that are cracked into smaller lighter fractions
31
what is the general formula for alkanes
CnH2n+2
32
why are alkanes classified as saturated hydrocarbons
they only have single carbon-carbon bonds, there are no double bonds
33
reactions of alkanes with halogens in the presence of ultraviolet radiation
Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation eg CH4 + Br2 → CH3Br + HBr methane + bromine → bromomethane + hydrogen bromide
34
what is the functional of alkenes
> C=C <
35
what is the general formula for alkenes
CnH2n
36
why are alkenes classified as unsaturated hydrocarbons
Compounds that have a C=C double bond are also called unsaturated compounds That means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds This makes them much more reactive than alkanes
37
reactions of alkenes with bromine
Alkenes undergo addition reactions in which atoms of a simple molecule add across the C=C double bond The reaction between bromine and ethene is an example of an addition reaction The same process works for any halogen and any alkene in which the halogen atoms always add to the carbon atoms across the C=C double bond eg H H H H I I I I C = C + Br2 -----> H - C - C - H I I I I H H Br Br
38
how can bromine water be used to distinguish between an alkane and an alkene
Alkanes and alkenes have different molecular structures All alkanes are saturated and alkenes are unsaturated The presence of the C=C double bond allows alkenes to react Bromine water is an orange coloured solution When bromine water is added to an alkane, it will remain as an orange solution as alkanes do not have double carbon bonds (C=C) so the bromine remains in solution as the alkane does not react with the bromine But when bromine water is added to an alkene, the bromine atoms add across the C=C bond, hence the solution no longer contains free bromine so it loses its coloure
39
how is an addition polymer formed
by joining up many small molecules called monomers (repeating units) together to form longer chain polymers addition monomers can only be formed from alkenes as the C=C bond breaks apart for example: 1000s of molecules of ethene together
40
problems in disposel of addition polymers
Addition polymers are formed by the joining up of many small molecules with strong C-C bonds This makes addition polymers unreactive and chemically inert so don’t easily biodegrade Polymers release a lot of heat energy when they burn and produces carbon dioxide which is a greenhouse gas that contributes to climate change Polymers that contain chlorine such as PVC release toxic hydrogen chloride gas when burned If incinerated by incomplete combustion, carbon monoxide will be produced which is a toxic gas that reduces the capacity of the blood to carry oxygen
41
which polyesters are biodegradable
bipolyesters
42
what functional group is alcohols
-OH
43
how can ethanol be oxidized
burning in air or oxygen (complete combustion) forms water and CO2 (microbial oxidation)bacteria in air use oxygen to oxidise ethanol forming ethanoic acid and water heating with potassium dichromate(VI) (oxidising agent) in dilute sulfuric acid to form ethanoic acid and water
44
manufacturing of ethanol - fermentation
add sugar/starch to water with yeast ferment the mixture at between 30-40c (to prevent the enzymes from denaturing) without oxygen for a few days yeast contains the enzymes that break down glucose into ethanol and CO2 when they respire anaerobically then the ethanol and water are separated by fractional distillation the yeast then denatures when the alcohol reaches 15% so the process has got to be constantly repeated (why fermentation is a batch process)
45
manufacturing of ethanol - hydration of ethene
hydrocarbons cracked to form ethene ethene and steam are passed over phosphoric acid (catalyst) requires: 300'c temp 60-70 atm pressure concentrated phosphoric acid catalyst
46
reasons for fermentation
carried out at a low temperature (30-40) does not require oxygen sugar is renewable does not pollute the environment
47
catalyst required to crack alkanes
silica or aluminum oxide
48
catalyst used when hydrating ethene
phosphoric acid
49
functional group of carboxylic acids
-COOH with a double bond between the C and first O and then the OH is also bonded to the C
50
reactions of carboxylic acids(aq) with metals
carboxylic acid + metal -> salt + hydrogen same as a regular acid reacting salt formed ends -anoate eg, ethanoic acid forms ethanoate
51
reactions of carboxylic acids(aq) with metal carbonates
carboxylic acid + metal carbonate -> salt + water + carbon dioxide salt formed ends -anoate
52
examples of carboxylic acids
vinegar which is an aqueous solution
53
functional group of esters
-COO- the first O is double bonded to the C and the other O is single bonded to the C
54
how is ethyl ethanoate formed
ester produced when ethanol and ethanoic acid react in the presence of an acid catalyst
55
displayed formula of ethyl ethonoate
, H H O H I I II I H-C-C-O-C-C-H I I I H H H
56
structural formula of ethyl ethanoate
CH3 CH2 CO2 CH3
57
how is an ester formed
carboxylic acid + alcohol -> ester + water need acid as catalyst usually sulphuric acid the ester is formed by combining the carboxylic acid and alcohol however the acid loses OH and the alcohol loses H which is where the water comes from
58
catalyst used for esters
any acid usually sulphuric
59
how to name an ester
first word is the prefix from the alcohol and ends in -yl second word is the prefix from the carboxylic acid and ends in -oate Eg, methanol + ethanoic acid -> methyl ethanoate + water
60
properties of esters
volatile compounds distinctive smells
61
uses of esters
food flavourings perfumes
62
practical: prepare a sample of an ester such as ethyl ethanoate
A mixture of ethanoic acid, ethanol and concentrated sulfuric acid is gently heated by either a water bath or an electric heater (ethanol is flammable, so a Bunsen can’t be used!) The ester is then distilled off as soon as it is formed and collected in a separate beaker by condensation As esters have low boiling points (they are volatile), they are the first to evaporate from the reaction mixture. Removing them from the mixture by distillation prevents the reverse reaction from occurring
63
how to draw the repeating unit of an addition polymer
One of the bonds in each C=C bond breaks and forms a bond with the adjacent monomer with the polymer being formed containing single bonds only so the monomer would be (ethene): H H I I C=C I I H H but when it forms a polymer (poly(ethene)): H H I I -(-C-C-)- n I I H H
64
how to draw polychloroethene
monomer: H Cl I I C=C I I H H repeating unit: H Cl I I -C-C- I I H H Polymer: H Cl I I -(-C-C-)- n I I H H
65
how to draw polypropene
monomer: H CH3 I I C=C I I H H repeating unit: H CH3 I I -C - C- I I H H polymer: H CH3 I I -(-C - C-)- n I I H H
66
how to draw polytetrafluoroethene
monomer: F F I I C=C I I F F repeating unit: F F I I -C - C- I I F F polymer: F F I I -(-C - C-)- n I I F F
67
how is a condensation polymer formed
a dicarboxylic acid and a diol react producing a polyester and water condensation polymers are formed from two different monomers joining and a water is lost per linkage
68
difference between addition and condensation polymers
addition forms only the polymer molecule condensation forms the polymer molecule and one water molecule per linkage addition are only formed by alkenes repeating condensation are formed from a diol and dicarboxylic acid alternating
69
what is a dicarboxylic acid
a regular carboxylic acid except the functional group is on both ends O O II II H-O-C-C-O-H
70
What is a diol
an alcohol with the functional group on both ends H H I I H-O-C-C-O-H I I H H
71
ethanedioic acid + ethanediol
monomers: O O II II n H-O-C-C-O-H + n H-O-CH2-CH2-O-H Polymer: O O II II -(-C-C-O-CH2-CH2-O-)- + 2n H2O

Chemistry (6 decks)

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