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OCR Chemistry A > 4.1 & 2 > Flashcards

4.1 & 2 Flashcards

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1
Q

Homologous series

A

A series of organic compounds having the same functional group with each successive member differing by CH2

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2
Q

Functional group

A

A group of atoms responsible for the characteristic reactions of a compound

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3
Q

Aliphatic

A

A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings

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4
Q

Alicyclic

A

An aliphatic compound arranged in a ring or without side chains

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5
Q

Aromatic

A

A compound containing a benzene ring

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6
Q

Saturated

A

Single carbon-carbon bonds only

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7
Q

Unsaturated

A

The presence of multiple carbon-carbon bonds, including double and triple carbon bonds and aromatic rings

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8
Q

Structural isomers

A

Compounds with the same molecular formula but with different structural formulae

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9
Q

Homolytic fission

A

In terms of each bonding atom, receiving one electron from the bonded pair, forming two radicals

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10
Q

Heterolytic

A

In terms of one bonding atom receiving both electrons from the bonded pair

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11
Q

Radical

A

A species with an unpaired electron

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12
Q

Alkanes

A

Saturated hydrocarbons containing single C-C and C-H bonds as sigma-bonds (with free rotation)

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13
Q

Sigma-bonds

A

Overlap of orbitals directly between the bonding atoms

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14
Q

Molecular orbital theory

A

Covalent bonds are formed by the overlap of atomic orbitals

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15
Q

Why can we draw alkanes in different ways

A

There is free rotation around these sigma bonds

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16
Q

Why do branched alkanes have low boiling points

A

Branched alkanes cannot pack together as well as linear alkanes
Less surface area of contact
So induced dipoles are less strong
Lower bp

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17
Q

Why do alkanes have low reactivity

A

Due to their high bond enthalpy
Not attracted to nucleophiles or electrophiles
C-C and C-H bonds are non polar
No partial charge anywhere

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18
Q

Shape of alkanes

A

Tetrahedral

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19
Q

Alkenes

A

Unsaturated hydrocarbons containing a double carbon bond comprising a pi-bond (restricted rotation) and a sigma-bond

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20
Q

Pi-bond

A

Sideways overlap of adjacent p-orbitals above and below the bonding C atoms

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21
Q

Shape of alkenes

A

Trigonal planar

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22
Q

Naming of alkenes

A

Stem, position of double bond, suffix

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23
Q

Stereoisomerism

A

Same structural formula but diff. arrangement of atoms in space

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24
Q

E/Z isomerism

A

Stereoisomer
Results from restricted rotation about the double bond
Requires 2 diff. groups to be attached to each carbon atom in the C=C group

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25
Q

Z isomers

A

Same group attached to both carbons, top and bottom

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26
Q

E isomers

A

Diff. group attached to both carbons, top and bottom

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27
Q

Formation of pi-bonds

A

P- orbitals perpendicular to C-C

Overlapping of orbitals

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28
Q

Cis isomerism

A

Usually Z isomers
Have higher bp
Polar
Have permanent dipole-dipole forces

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29
Q

Trans isomers

A

Non polar
Usually E isomers
Have higher mp
Pack more efficiently so IM forces maximise potential strength

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30
Q

Why are alkenes reactive

A

Exposed areas of high electron density that is attractive to electrophiles
Pi-bonds have a low bond enthalpy
Sigma-bonds in alkanes have higher bond

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31
Q

Addition reaction

A

When a reactant is added to an unsaturated molecule to make a saturated molecule
Breaks pi-bonds and forms sigma-bonds

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32
Q

Hydrogenation

A

H2 gas at high temp with Ni catalyst

1 mole of H2 per double bond

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33
Q

Alkenes react with:

A 
H2
Halogens
Hydrogen halides (HF/HCl/HBr/ HI)
Other H-X molecules e.g. H2SO4
Steam
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34
Q

Hydration

A

Reaction with water

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35
Q

Conditions of hydration

A

Steam
H3PO4 catalyst
300 degrees
60 atm

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36
Q

Where do curly arrows start

A

A lone pair

Existing covalent bond

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37
Q

Markownikoff’s rule

A

H atoms/ least electro-ve atoms join the carbon which already has the most H atoms directly bonded (most stable carbocation)

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38
Q

Most stable carbocation intermediate

A

Tertiary (3’) - 3 alkyl groups
Secondary (2’) - 2 alkyl groups, 1 H
Primary (1’) - 1 alkyl group, 2 H

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39
Q

What happens when you add an alkyl group

A

Donate electrons to positive charge and minimise strength

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40
Q

General formula of alcohols

A

CnH(2n+2)O

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41
Q

Functional group of alcohols

A

Hydroxyl group: -OH

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42
Q

Naming of alcohols

A

The no. of the carbon to which the hydroxyl group is attached is written before the -ol

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43
Q

Making ethanol

A

Ethene (g) + water (g) –> ethanol (l)

Fermentation of sugar - C6H12O6 —> 2C2H5OH + 2CO2

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44
Q

Conditions to make ethanol

A

Phosphoric acid catalyst - dipole of water isn’t a strong enough electrophile
300 degrees
60 atm

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45
Q

Why does solubility of alcohols decrease with chain length

A

They behave more like hydrocarbons and the LF’s have a greater influence on solubility than the -OH group

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46
Q

Primary alcohols

A

OH bonded to C with 1 alkyl group

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47
Q

Secondary alcohols

A

OH bonded to C with 2 alkyl groups

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48
Q

Tertiary alcohols

A

OH bonded to C with 3 alkyl groups

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49
Q

Why do alcohols have high mp and bp

A

Hydrogen bonding

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50
Q

Which alcohols can be oxidised

A

Primary and secondary alcohol using a suitable oxidising agent e.g. acidified dichromate ions (Cr2O7 ^2-/ H^1)

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51
Q

What is the colour change in acidified dichromate ions when oxidised

A

Orange to green

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52
Q

Partial/mild oxidation of primary alcohols

A

Primary alcohol + [O] –> Aldehyde and water

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53
Q

Aldehydes

A

End in -al

C=OH functional group (always at the end; don’t need numbers)

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54
Q

Conditions of partial/mild oxidation of primary alcohols

A

K2Cr2O7/H2SO4

Distil immediately

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55
Q

Complete oxidation of primary alcohols

A

Primary alcohol + 2[O] –> Carboxylic acid + water

56
Q

Conditions of complete oxidation of primary alcohols

A

K2Cr2O7/H2SO4

Reflux

57
Q

Complete oxidation of secondary alcohols

A

Secondary alcohols + [O] –> Ketone + water

58
Q

Conditions of complete oxidation of secondary alcohols

A

K2Cr2O7/H2SO4

Reflux

59
Q

Ketones

A

End in -one

C=O carbonyl functional group

60
Q

Can ketones be oxidised

A

No

61
Q

Can tertiary alcohols be oxidised

A

No

62
Q

Dehydration reaction

A

Alcohol –> alkene (in the presence of acid catalyst (conc. H3PO4/ H2SO4)), heated under reflux

63
Q

Forming halogenoalkanes

A

Substitution with halide ions in the presence of acid (NaBr/H2SO4)

NaBr + H2SO4 —> HBR + NaHSO4
CH3CHOHCH3 + HBr –> CH3CHBRCH3 + H2O

64
Q

Nucleophile

A

Electron pair donor

65
Q

Examples of nucleophiles

A

OH ^-
Cl ^-
H2O

66
Q

Haloalkanes

A

Compounds in which a halogen has replaced at least one hydrogen (CnH2n+1X)

67
Q

Classification of haloalkanes

A

Primary, secondary and tertiary depending on no. of alkyl groups

68
Q

What dictates the reactions of haloalkanes

A

The polarity of the C-halogen bond

69
Q

What happens as a result of the carbon atom on the C-halogen bond being electron deficient

A

The partial positive charge attracts species with lone pairs (nucleophiles)

70
Q

Nucleophilic substitution

A

Nucleophile replaces a halogen

CH3CH2I + OH –> CH3CH2OH + I

71
Q

Ozone layer

A

O3

72
Q

What do CFC’s do

A

Deplete the ozone layer

O3 + O (oxygen radical) –> 2 O2

73
Q

Rates of hydrolysis in haloalkanes

A

Increase from F to I due to the decrease in bond enthalpies so ppt is formed faster in iodoalkanes and slowest in chloroalkane

74
Q

Heterolytic fission

A

The breaking of a covalent bond to form an anion and cation as both electrons go to one species

75
Q

Homolytic fission

A

The breaking of a covalent bond to form 2 radicals, with each species receiving one electrons

Happens in the presence of UV light

76
Q

Equipment for reflux

A 
Pear shaped flask 
Condenser 
Rubber tubing
Stand and clamp 
Heat source
77
Q

Why are anti-bumping granules used

A

So the contents boil smoothly without large bubbles forming, which will cause the glassware to vibrate

78
Q

Apparatus for distillation

A 
Round bottom or pear shaped flask 
Condenser 
Rubber tubing 
Heat source 
Stand and clamp 
Screw cap adaptor 
Receiver adaptor 
Thermometer
79
Q

In samples of organic liquids, how do you identify the organic layer

A

Add water to the mixture. The layer that gets bigger is the aqueous layer

80
Q

How to use a separating funnel

A

Ensure the tap is closed
Pour the mixtures in and put on a stopper before inverting
Allow layers to settle and identify the organic layer
Place conical flask under the separating funnel, remove the stopper and open the tap until the whole lower layer has left
Do the same for the second layer

81
Q

How to purify products with any acid impurities

A

Add NaH/CaCO3 (aq) and shake the mixture in the separating funnel

82
Q

Drying agent

A

Anhydrous inorganic salt that readily takes up water to become hydrated e.g. CaCl2, CaSO4, MgSO4

83
Q

Which fragment ion has a m/z of 15

A

CH3 +

84
Q

Which fragment ion has a m/z ratio of 29

A

C2H5+

85
Q

Which fragment ion has a m/z ratio of 57

A

C4H9 +

86
Q

Which fragment ion has a m/z ratio of 43

A

C3H7 +

87
Q

Which fragment ion has a m/z ratio of 31

A

CH2OH

88
Q

Which fragment ion has a m/z ratio of 45

A

C2H5O +

89
Q

Using M and M + 1 peaks

A

Height of M + 1 peak/height of M peak * 100 = no. of carbon atoms

90
Q

What does the amount that a bond stretch or bends depends on

A

Mass of atoms in the bond - heavier atoms vibrate more slowly than lighter ones
The strength of the bond - Stronger bonds vibrate faster than weaker bonds

91
Q

Advantages of oil companies using cyclic alkanes

A

Lower boiling point so will burn more efficiently

91
Q

What is the greenhouse effect of carbon dioxide dependent on

A

Abundance in atmosphere

Ability to absorb IR

91
Q

CCS

A

Reacting CO2 and metal oxides (CaO)

Deep in oceans

92
Q

CIP priority rules

A

If both high priority groups are at the top it’s a (Z) isomer
If they are diagonal, (E)

93
Q

Benefits of developing biodegradable and photodegradable polymers

A

Reduced dependency on finite resources

Alleviating problems from disposal of persistent plastic waste

94
Q

Cis-trans isomerism

A

Special case of E/Z isomerism in which 2 of the substituent groups attached to each carbon of the C=C group are the same

95
Q

Disposal of waste polymers

A

Combustion which can produce energy
Use as organic feedstock for production of plastics
Dissolving halogenated plastics (PVC) so toxic HCl isn’t released

96
Q

What does IR cause

A

Covalent bonds to vibrate more and absorb energy

97
Q

Which bonds absorb IR

A

C=O
O-H
C-H

98
Q

What is infrared spectroscopy used for

A

Monitor gases causing air pollution (CO and NO from cars)

Measure ethanol in the breath (breathalysers)

99
Q

What is the M+1 peak caused by

A

Small proportion of carbon-13

100
Q

When do we use cis/trans isomers

A

When each carbon in the double bond is attached to one H

101
Q

Why does the bp of cycloalakanes increase

A

More carbons —> stronger London Forces

More energy need to overcome imf

102
Q

Why do cycloalkanes get added to straight chain alkanes in petrol

A

So it burns more efficiently

103
Q

What is the greenhouse effect of CO2 dependent on

A

Abundance in atmosphere

Ability to absorb IR

104
Q

Why do we do reflux

A

To keep the product reacting in the reaction flask until collection

105
Q

Liebig condenser

A

Allows the product to distill off and be collected

106
Q

Why is ethanol used in the investigation about carbon-halogen bond enthalpy

A

So the reaction with AgNO3 is slow enough to be observed

107
Q

What happens to bromine water in the presence of alkenes

A

Decolourises

108
Q

Process of mass spectrometry

A

The IR causes the molecule to become charged and they are then accelerated through a capillary and detected

109
Q

Heating under reflux

A

Boiling a liquid in a vertical container to prevent loss of products

110
Q

How to remove acidic impurities

A

Shaking with potassium hydrogen carbonate ions

111
Q

M/z peak of 45

A

COOH +

112
Q

Why can cracking produce a variety of alkanes and alkanes w/ diff chain lengths

A

C-C bonds can break anywhere

113
Q

Steps in purifying an organic liquid

A

Allow mixture to cool
(If reflux decant reaction mixture from the anti-bumping granules)
Use a separating funnel and discard aq layer
Dry using an anhydrous salt e.g. MgSO4 then filter off and discard
Redistillation - collect distillate in range just below (and up to) the bp of product

114
Q

Why are there many products in free radical substitution

A

More than one C-H bond can be substituted
Lots of termination steps
Termination steps can give products that will also react w/ radicals

115
Q

Feedstock recycling

A

Chemical or thermal processes which can use waste polymers to regenerate monomers, oils or gases so that new polymers can be produced

118
Q

Why are there still concerns about ozone depletion

A

CFC’s are still being used

Other ozone depleting substances

119
Q

Miscible with

A

Soluble in

120
Q

Purifying a liquid that is miscible with water

A

Allow mixture to cool
Decant reaction mixture from anti-bumping granules, if reflux
Use separating funnel and keep aq layer
If acid is present use Na2CO3 (aq) until effervescence stops
Redistil

121
Q

Purifying a solid product

A

Allow reaction mixture to cool
Filter under reduced pressure and leave impure product to dry
Recrystallise
Filter under reduced pressure, rinse w/ ice-cold water and leave the crystals to dry
Measure mp to assess purity
Repeat 2 previous steps if required

122
Q

Filtering under reduced pressure

A

Using a Buchner funnel

123
Q

Process of recrystallisation

A

Transfer impure solid to a boiling tube
Dissolve in minimum quantity of hot solvent (usually water)
Filter hot solution to remove any solid impurities
Allow filtrate to cool slowly to room temp, and then in an ice bath
Crystals will form

124
Q

Determining mp of an organic solid

A

Ensure sample is dry
Add about 3mm of the sample to a sealed glass capillary tube
Measure mp using a Thiele tube setup

125
Q

Mp of pure vs impure product

A

Pure products should have fairly narrow mp range

Impure products will have a LOWER and WIDER mp range

126
Q

Experiment plan for rate of hydrolysis of haloalkanes

A

Measure 1cm^3 of each haloalkane and place in separate test tubes
Add 1cm^3 of ethanol solvent to each tube
Place in a water bath at 60 degrees
Once all tt have reached the same temp, add 1cm^3 of aq AgNO3 to one of the test tubes she use a stopwatch to time how long it takes for the ppt to form
Repeat w/ other two solutions

127
Q

Heating alcohols under reflux

A

Place 2 cm^3 of acidified dichromate and 1 cm^3 alcohol (in excess) in a pear shaped flask and attach condenser
Heat sol. under reflux w/ a heating mantle

128
Q

Distillation to form an aldehyde

A

Place the dichromate, acid and 1’ alcohol (in excess) in a pear shaped flask and attach a condenser
Use thermometer to ensure temp is below 100
Solution will turn green as the aldehyde is produced
-al can’t H bond and has the lowest bp
Collect distillate in the range just below (and up to) the bp of the -al. It will condense in the receiver

129
Q

Carrying out TLC

A

Take a TLC plate and draw base line 1cm from one end of plate
Use a capillary tube and spot a small amount of sol onto base line
Prepare chromatography tank
Place the prepared TLC plate in the beaker, making sure that the solvent does not cover the spot
Cover the beaker w/ watchglass

130
Q

Making a chromatography tank

A

This can be made from a small beaker w/ watchglass on top

Pour solvent into beaker to a depth of about 0.5 cm

131
Q

Determining conc using gas chromatography

A

Measure the peak integration value of desired peak from compound X
Prepare some standard solutions of diff, known conc. of the compound X
Run these through the GC and ensure your peak integration values
Plot a calibration graph of peak integration value vs conc. and plot LOBF
Find the peak integration value and read off corresponding conc.

132
Q

Limitations of free radical substitution

A

Further substitution occurs, producing a variety of products
Substitution can occur at different positions in the carbon chain
Produces several by-products lowering atom economy

133
Q

Bond enthalpy of 1’, 2’ and 3’ haloalkanes

A

Tertiary has the lowest bond enthalpy so shortest time to react with silver nitrate

134
Q

How is infrared spectroscopy used in identifying air pollutants

A

Indentifies bonds in pollutant
Match spectrum to known pollutants
Measures conc of pollutant

135
Q

Naming esters

A

Stem is -ol attached to rhs

Suffix is -COOH attached to lhs

OCR Chemistry A (16 decks)

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