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(A-level) Chemistry > Module 4.2 > Flashcards

Module 4.2 Flashcards

(60 cards)

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1
Q

What is the general formula of alcohols

A

CnH2n+1 OH

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2
Q

What is a primary alcohol

A

When the OH Group is attached to a carbon with 1 alkyl chain

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3
Q

What is a secondary alcohol

A

When the OH Group is attached to a carbon with 2 alkyl chains

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4
Q

What is a tertiary alcohol

A

When the OH Group is attached to a carbon with 3 alkyl chain

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5
Q

How does alcohol boiling / melting point change with chain length

A

As chain length increases, boiling / melting point increases.

This is because surface contact increases so the london forces are stronger

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6
Q

Why is the boiling point of alcohols higher than alkenes

A

As hydrogen bonds form between the OH groups between the molecules

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7
Q

What is the solubility of alcohols

A

Water molecules and the OH groups of alcohol are polar.
Because of this, methanol, ethanol and propanol are soluble in water

As the alkyl chain increases the solubility of the alcohol decreases. (As the alkyl chain cant form hydrogen bonds)

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8
Q

What is produced in the complete combustion of alcohols

A

Water and carbon dioxide

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9
Q

What oxidation reagents are used when oxidising an alcohol and what symbol is used to represent them

A

K2Cr2O7

Or

H2SO4

The symbol is [O]

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10
Q

What is produced in oxidation of a primary alcohol under distillation conditions

A

An Aldehyde and water

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11
Q

What is produced by the oxidation of a primary alcohol under reflux conditions

A

A carboxylic acid and water

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12
Q

What is produced by the oxidation of a secondary alcohol under reflux

A

A ketone is produced (+ water)

The ketone will undergo no further reactions

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13
Q

What is reflux

A

The constant boiling and condensing of a reaction mixture

It ensures that the reaction goes to completion as fully as possible without losing reactants or products

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14
Q

What is esterification

A

The chemical reaction to make an ester

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15
Q

What are esters

A

Organic compounds that contain a -COOR functional group, where R is an alkyl chain.

It is embedded within the chain

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16
Q

What are esters used for

A

They are used in the manufacture of foods because they have a pleasant fruity smell

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17
Q

How are esters made using alcohols

A

A reversible reaction WITH AN ACID CATALYST

Carboxylic acid + alcohol → ester + water

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18
Q

How are esters named

A

The first part is the name of the alkyl chain (emg ethyl)
The second part is the stem of the carboxylic acid + oate

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19
Q

What is dehydration

A

A chemical reaction where water is lost from an organic compound

It is an ELIMINATION reaction

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20
Q

What is the reagent of dehydration of alcohols

A

sulphuric acid or phosphoric acid

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21
Q

What is the product produced by dehydration of alcohols (and how does the reaction occur)

A

An alkene and water

The reaction occurs under reflux with a concentrated acid

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22
Q
A
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23
Q

What is a strong acid

A

An acid that is completely ionised

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24
Q

What is a weak acid

A

An acid that is only partially ionised (low concentration of H+ ions)

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25
What is a dilute acid
There is a low concentration of acid molecules compared to water molecules
26
What is a strong acid
There is a high concentration of acid molecules compared to water molecules
27
What is nucleophilic substitution
A reaction where an atom (typically a halogen) or group of atoms is exchanged for a nucleophile. The nucleophile is attracted to the partially positive charge on the carbon atom (caused by electronegativity)
28
What are some common nucleophiles
:OH- :NH3 :CN-
29
30
What symbol represents a nucleophile
Place a colon before the ion :NH3
31
What is the reaction mechanism of nucleophilic substitution with ammonia (sadly arrows can't be drawn)
H. H H H-c-cl. + :NH3. →. H-c-N+-h + :Cl- H. H H H. H. H H H-c-N+-H + :NH3 → H-C-N. + NH4 + :cl- H. H. H H
32
What are CFCs
A class of organic compounds that contain chlorine and fluorone atoms - ChloroFluroCarbons They are gasses at room temperatures
33
What happens to CFCs in the stratosphere
In the stratosphere they begin to be exposed to UV light This causes the C-Cl bond to undergo homolytic fission Creating cl and C free radicals
34
What is the Ozone layer
A layer in the stratosphere that contains O3 molecules It absorbs UV light and
35
What reactions occur in the stratosphere
Homolytic fission of CFCs produced chlorine free radicals (initiation) The Chlorine free radicals reacts with ozone to make a ClO radical and O2 The ClO radical reacts with O3 to regenerate the Cl radical and produce oxygen
36
Why is the ozone layer shrinkinh
As chlorine free radicals are reacting with it to produce oxygen
37
What is a quickfit apparatus
A selection of heat-resistant glassware with connectors that allow it to be fitted in a variety of arrangements Before fitting the connectors grease the joints slightly with petroleum jelly
38
What is distillation
A separating technique which is often used to separate a product from an organic synthesis reaction
39
How do you use a separating funnel
Use a separating funnel: Mount an iron ring on a clamp and put the separating funnel in it. Remove the stopper and make sure that the tal at the bottom is closed. Poor the mixture into the funnel so that it is less than half full Wash out the reaction vessel (e.g beaker organic compound was made in) with water and add to the funnel) Put the stopper back in, take the funnel out and invert it. Gently shake the mixture until the pressure is equalised place the funnel back into the iron ring and give time for the liquids to form two layers Place a beaker under the funnel and open the tap to collect the lower layer (water). Close the tap Using a new clean beaker, collect the organic product
40
What is redistillation
The process of purifying a liquid by performing multiple distillations
41
How do you use drying agents
Add a few spatulas of the drying agent to the organic compound If the drying agent clumps add more When the drying reagent remains free moving the product is dry Collect the filter (the dry organic product) via filteation
42
What are drying agents
Anhydrous salts that slowly absorb water
43
What are separating funnels
A piece of equipment that is used to separate immiscible liquids (liquids that do not mix with each other)
44
What happens when a bond absorbs infrared radiation
The bond vibrates in stretching or bending motions
45
What determines the way a bond vibrates
The strength of the bond The length of the bond The mass of each aton in the bond
46
What are molecular ions
Positive ions formed in mass spectrometry
47
What is fragmentation
A process where an ion is split into pieces, one of which is a positive fragment ion and the other is a neutral speices
48
49
What happens in mass spectroscopy
Ionisation - 1 Atoms are ionised by removing 1 electron, making a positive ion (fragmentation also occurs) Acceleration - 2 Ions are accelerated so that they have the same kinetic energy Deflection - 3 Ions are deflected by a magnetic field according to their masses and the charge Detection - 4 The beam of ions passing through the machine is detected electrically
50
What determines how much the ions are deflected in mass spectroscopy
Their mass - lighter ions are deflected more Their charge - the greater the charge, the greater the deflection
51
What are the uses of mass spectroscopy
Determine the abundance of each isotope of an element Identifying unknown compounds
52
What is the mass of the molecular ion in mass spectroscopy
The mass of the molecular ion is the same as the mass of the compound the molecular ion comes from
53
What causes fragmentation in mass spectroscopy
Excess energy from ionisation is transferred to the molecular ion making it vibrate This causes bonds to weaken and the molecule can fragment
54
What are neutral species (mass spectroscopy)
A species produced by fragmentation that has no charge
55
Are neutral species detected in mass spectroscopy
No they are not detected
56
57
How are infrared spectrums created
Bonds absorb specific values of infrared radiation When infrared radiation is absorbed, a trough is created, as the percentage transmittance is lower
58
What are the axis of infrared spectrum
Transmittance % (of IR) Wavelength cm³ (decreasing)
59
How are bonds identified from an infrared spectrum
Bonds have known IR absorption values, and therefore known transmittance values These values are compared to the infrared spectrum graph created
60
How can you identify that an alcohol has been oxidised
The Cr in potassium dichromate will be reduced from +6 to +3 This causes the solution to change from orange to green

(A-level) Chemistry (9 decks)

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