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Chemistry > 4 Organic Chemistry > Flashcards

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
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

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)

20
Q

what is isomerism

A

Isomers are compounds that have the same molecular formula but different displayed formulae

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 R-OH alcohol
but.. 4 ..anoic acid R-C=O-OH carboxylic acid
pent.. 5 ..amine R-NH2 amine
hex.. 6 ..yl ..anoate R-C=O-O-R 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

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.

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

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

25
Q

effects of carbon monoxide on the capacity of blood to carry oxygen

A

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
Q

what do the high temperatures in car engines allow

A

the temperature goes high enough to allow and oxygen from the air and nitrogen to react, forming oxides of nitrogen (NO and NO2)

27
Q

how does the combustion of some impurities in hydrocarbon fuels results in the formation of sulfur dioxide

A

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
Q

how does sulfer dioxide and and oxides of nitrogen contribute to acid rain

A

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
Q

process of catalytic cracking

A

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
Q

why is cracking necessary

A

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
Q

what is the general formula for alkanes

A

CnH2n+2

32
Q

why are alkanes classified as saturated hydrocarbons

A

they only have single carbon-carbon bonds, there are no double bonds

33
Q

reactions of alkanes with halogens in the presence of ultraviolet radiation

A

Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation

eg CH4 + Br2 → CH3Br + HBr

methane + bromine → bromomethane + hydrogen bromide

34
Q

what is the functional of alkenes

A

> C=C <

35
Q

what is the general formula for alkenes

A

CnH2n

36
Q

why are alkenes classified as unsaturated hydrocarbons

A

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
Q

reactions of alkenes with bromine

A

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
Q

how can bromine water be used to distinguish between an alkane and an alkene

A

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 in ways that alkanes cannot
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
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 colour

39
Q

how is an addition polymer formed

A

by joining up many small molecules called monomers

40
Q

problems in disposel of addition polymers

A

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
Q

which polyesters are biodegradable

A

bipolyesters

Chemistry (5 decks)

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