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A-level Chemistry > Topic 6 - Organic I > Flashcards

Topic 6 - Organic I Flashcards

(68 cards)

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1
Q

Homologous series

A

A series of compounds with the same functional group and similar chemical properties (e.g, alkanes)

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2
Q

Functional group

A

The group of atoms responsible for the characteristic reactions of a particular compound (e.g. COOH for carboxylic acids)

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3
Q

Empirical formula

A

the simplest whole number ratio of atoms of each element in a compound

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4
Q

Molecular formula

A

the true number of atoms of each element in a compound

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5
Q

General formula

A

All members of a homologous organic series follow the general formula e.g. CnH2n+2 for alkanes

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6
Q

Structural formula

A

shows the structural arrangement of atoms within a molecule without the bonds

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7
Q

Displayed formula

A

shows every atom and every bond in an organic compound

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8
Q

Skeletal formula

A

Shows only the bonds in a compound and any non-carbon atoms. The vertices are carbon atoms and hydrogen is assumed to be bonded to them unless stated otherwise.

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9
Q

Addition

A

reactants combine to form a single product

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10
Q

Substitution

A

one functional group is replaced by a different one

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11
Q

Elimination

A

reactions in which two atoms, or groups of atoms, are removed from a molecule to form a new product

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12
Q

Oxidation

A

when a species loses at least one electron and gains oxygen

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13
Q

Reduction

A

when a species gains at least one electron and loses oxygen

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14
Q

Hydrolysis

A

a reaction which uses water to break down a compound

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15
Q

Polymerisation

A

a reaction in which many small molecules (monomers) join together to form a long, repeating molecule (polymer)

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16
Q

Isomers

A

molecules with the same molecular formula but a different arrangement of atoms within the molecule

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17
Q

Position isomers

A

when the functional group of the molecule is in a different position on the carbon chain (e.g., propan-1-ol vs propan-2-ol)

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18
Q

Functional group isomers

A

isomers that have the same molecular formula but different functional groups (e.g. propanal vs propanone)

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19
Q

Stereoisomerism

A

molecules with the same molecular and structural formula but a different arrangement of atoms in space

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20
Q

E isomer

A

groups are on opposite sides of the double bond

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21
Q

Z isomer

A

groups are on the same side of the double bond

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22
Q

CIP Priority Rules

A

The first atom directly bonded to the carbon with the double bond with the highest Ar is given the higher priority

these groups are used to determine if it is the E or Z isomer

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23
Q

cis- trans- isomerism

A

a special case of E-Z isomerism

can only be used when there are hydrogen atoms to compare the two other groups to

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24
Q

General formula for alkanes

A

CnH2n+2

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25
An alkane is which type of hydrocarbon?
saturated, as they do not contain double bonds
26
Fractional distillation
- mixture of hydrocarbons is vapourised and enters the fractionating column - vapours rise, cool and condense - products are collected for different uses - short-chain hydrocarbons that have lower boiling points rise higher up the column before reaching their boiling point (and vice versa)
27
Reforming
the processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion
28
Cracking
the breaking down of long chain hydrocarbons into smaller, more useful molecules
29
Pollutants that form during combustion of alkane fuels
- carbon monoxide (toxic) - oxides of nitrogen and sulfur (acidic) - carbon particulates - unburned hydrocarbons
30
Alternative fuels
- biofuels renewable fuels comes from living matter biodiesel - made from refining renewable fats and oils bioethanol - fermentation carbon neutral
31
Homolytic fission
breaking a covalent bond so that each atom takes an electron from the bond to form two free radicals
32
Heterolytic fission
breaking a covalent bond so that the more electronegative atom takes both the electrons from the bond to form an anion, leaving behind a cation
33
Limitations of FRS
- collisions are uncontrollable, so FRS cannot be used to make one particular product - more collisions are inevitable even after two propagations happen, causing further substitutions to happen
34
General formula for alkenes
CnH2n
35
Alkenes are what kind of hydrocarbon?
alkenes and cycloalkenes are unsaturated hydrocarbons, as they contain a C=C double bond
36
π bond
a covalent bond formed when p orbitals of two carbon atoms overlap with each other (formed above and below the plane of the molecule)
37
σ bond
a covalent bond formed from the end to end overlap of atomic orbitals
38
Electrophile
a chemical species which is attracted to electrons
39
Relative stability of carbocation intermediates
tertiary > secondary > primary > methyl In a tertiary carbocation, where the positively charged carbon is attached to three alkyl groups, there is maximum electron donation to stabilise the positive charge.
40
Bromine water test
alkenes cause bromine water to change from orange-brown to colourless as C=C bond can 'open up' to accept bromine atoms to become saturated
41
Hydrogenation of alkenes
- hydrogen - nickel catalyst - 160 degrees electrophilic addition whereby alkanes are produced used in manufacture of margarine from unsaturated vegetable oils
42
Halogenation of alkenes
- halogens add across the double bond - each carbon atom bonds to one halogen atom - electrophilic addition
43
Hydrogen halides and alkenes
- halogenoalkanes formed - electrophilic addition
44
Reaction of alkenes with steam
- forms alcohols - steam hydration - 300˚ - 60-70 atom - phosphoric acid catalyst
45
Reaction of alkenes with potassium manganate
- shake alkene with acidified potassium manganate(VII) - purple solution decolourised, oxidised alkene to diol e.g. ethene -> ethane-1,2-diol
46
Disposal of polymers
- recycling - incineration to release energy - use as feedstock for cracking
47
How to limit problems caused by polymer disposal
- developing biodegradable polymers - removing toxic waste gases by incineration of plastics
48
Nucleophile
an electron-rich species that can donate a pair of electrons
49
Halogenoalkanes
- contain polar bonds since halogens are more electronegative than carbon - electron density is drawn towards hydrogen, forming 𝝳+ and 𝝳- regions
50
Halogenoalkanes -> alcohols
- halogenoalkanes react with aqueous KOH or NaOH - nucleophilic substitution - hydroxide ion acts as nucleophile
51
Halogenoalkanes and silver nitrate
- broken down using silver nitrate and ethanol - water acts as nucleophile, which leads to breakdown of halogenoalkane, releasing halide ions into the solution - halide ions react with silver ions to form silver precipitates
52
Halogenoalkanes -> nitriles
- react with KCN to form nitriles - nucleophilic substitution - CN- acts as nucleophile - reaction adds one carbon atom
53
Halogenoalkanes -> amines
- react with alcoholic ammonia (e.g. ethanolic NH3) - nucleophilic substitution - Ammonia is nucleophile
54
Halogenoalkanes -> alkenes
- react with ethanolic potassium hydroxide (KOH) to produce alkenes - elimination - hydroxide ion acts as base
55
Relative reactivity of halogenoalkanes
tertiary > secondary > primary
56
Trend in reactivity of chloro-, bromo- and iodoalkanes in terms of bond enthalpy
C-I weakest bond, lowest bond enthalpy, bond breaks easier, react faster the larger the halogen, the longer the C-X bond, so the lower the bond enthalpy
57
Alcohol + oxygen products
carbon dioxide + water
58
Alcohol + halogenating agents
- nucleophilic substitution - -OH group is replaced by a halogen, producing a halogenoalkane
59
Alcohol -> choloroalkanes
- PCl5 - can be used to test for alcohols as white fumes produced turn damp blue litmus paper red
60
Alcohol -> bromoalkanes
- 50% concentrated sulfuric acid + potassium bromide - potassium bromide reacts with sulfuric acid to form HBr - this then reacts with the alcohol to produce the bromoalkane CH3CH2OH + HBr -> CH3CH2Br + H2O
61
Alcohol -> iodoalkanes
- red phosphorus and iodine - phosphorus reacts with iodine to produce phosphorus (III) iodide - this then reacts with the alcohol to form the iodoalkane 2P + 3I2 -> 2PI3 3CH3CH2OH + PI3 -> 3CH3CH2I + H3PO3
62
Oxidation of alcohols
primary alcohols -> aldehydes -> carboxylic acids secondary alcohols -> ketones tertiary -> not oxidised potassium dichromate (VI) in dilute sulfuric acid
63
alcohols -> alkenes
- concentrated phosphoric acid - elimination - dehydration (water removed from alcohol)
64
Fehling's solution colour change
- gently warm - aldehyde present = red precipitate - no aldehyde = remains blue
65
Heating under reflux
- vertical Liebig condenser - continuously boil and evaporate mixture - vapours evaporate, condense and return to the flask for further heating
66
Distillation
- pear-shaped flask heated - liquid with lower boiling point will evaporate first - it rises out of the flask into tubing surrounded by condenser - condenser cools and condenses vapour back into liquid - liquid is collected in separate flask
66
Extraction with solvent in separating funnel
- pour mixture in separating funnel - add water - shake funnel - separate organic and aqueous layer - collect in two different containers
67
Drying with anhydrous salt
- add anhydrous salt - will absorb moisture and water present, drying and purifying compound - common salt is sodium sulfate

A-level Chemistry (8 decks)

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