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A Level > Chemistry paper 2 corrections > Flashcards

Chemistry paper 2 corrections Flashcards

1
Q

How does purity affect melting points?

A

Impure compounds have lower melting points

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2
Q

Alcohol to haloalkane

A

NaCl and H2SO4

Forms product and NaHSO4 and H2O

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3
Q

What is an easy trick they can play when oxidising alcohols?

A

Tertiary alcohols dont oxidise

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4
Q

What is the number on [O] when oxidising to aldehydes/ketones?

A

1

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5
Q

What is the number on [O] when oxidising to carboxylic acids?

A

2

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6
Q

What happens when HCl acid is added to molecules such as amino acids?

A

NH2 becomes NH3+Cl- salt

COOH is not affected

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7
Q

What happens when NaOH alkali is added to molecules such as amino acids?

A

NH2 not affected
COOH becomes COO-Na+ salt
OH on phenols become O-NA+

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8
Q

Why are phenols more reactive than benzene?

A

OH partially delocalises into the pi system
The electron density increases
The phenol is more susceptible to an electrophilic attack

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9
Q

How does the halogen affect the rate of reaction?

A

Iodine is less reactive, so has a weaker bond, so the reaction is faster
Chlorine is more reactive, so has a stronger bond, so the reaction is slower

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10
Q

What is the correct wording when talking about E/Z isomers

A

Priority groups

Largest atomic number

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11
Q

Test for an aldehyde

A

Tollens’ reagent

Silver mirror

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12
Q

Test for carbonyls

A

2,4-DNP
Orange precipitate produced
Can use the melting points of the precipitate to determine to compound by comparing them to predetermined values

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13
Q

nitrile to amine

A

Reduction
LiALH4 and H2SO4
Or H2 and Ni catalyst (this is the same as for alkene to alkane)

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14
Q

WHat is easy to forget when reducing aldehydes

A

The carbon on the C=O is easy to miss when it becomes an alcohol

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15
Q

Nitrile to a carboxylic acid

A

H2O, dilute HCL and reflux

Can sometimes be said to just be H+

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16
Q

How are major and miner products determined in electrophilic addition?

A

Less reactive atom attaches to the carbon with the most hydrogens

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17
Q

What happens when you add Na2CO3 to phenol?

A

COOH becomes COO-Na+

OH is not affected

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18
Q

What affects boiling points?

A

Non polar molecules- London forces

Polar molecules- hydrogen bonding

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19
Q

Purification steps

A 
-Dissolve impure solid in MINIMUM volume of hot solvent
Cool solution
FIlter solid to remove impurities
Recrystalisation
Scratch with a glass rod
Wash with a cold solvent and dry
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20
Q

What is an addition reaction?

A

When two molecules become one

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21
Q

Why do boiling points of simple covalent molecules increase down the group?

A

Because they’ve got more electrons

So they have more/stronger London forces

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22
Q

Why does reactivity down group 2 increase?

A

Because there is more electron shielding
Electrons are less attracted to the nucleus
Ionisation energy decreases
Less energy is needed to remove an electron

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23
Q

What is the charge on NO3?

A

-1

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24
Q

What counts as a H NMR environment which can often be missed?

A

The hydrogen on the OH group

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25
Q

What is the most acidic- amide, carboxylic acid, ester or acyl chloride?

A

Acyl chloride

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26
Q

Why does a branched compound have a lower boiling point to an unbranched compound?

A

Because there are less points of contact
Less surface interaction
Less London forces can form
Less energy is needed to break the London forces

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27
Q

What is the definition of stereoisomers?

A

Molecules that have the same structural formula but a different arrangement in space

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28
Q

How does a molecule act as an electrophile?

A

It accepts a lone pair of electrons

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29
Q

Why is one of the products of electrophilic addition a major product?

A

Because the carbocation intermediate is more stable (the one with the + on it) when the hydrogen bonds to the carbon with the most hydrogens on it

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30
Q

How do you check the purity?

A

Melt in a capillary tube
Find the melting point
Compare to known values
If it is a sharp melting point close to the known value, it is pure

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31
Q

How does an electron donating group work?

A

It donates a PAIR of electrons/LONE PAIR into the benzene ring
or
It is DELOCALISED into the benzene ring

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32
Q

When is a halogen carrier needed?

A

When it is a benzene or when there is an electron withdrawing group

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33
Q

What is the product when an amine reacts with an acid?

A

NH3+Cl-

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34
Q

What is the structure of a hydrogen bond?

A

The H on the H2O binds to the lone pair on the O on the molecule.
Make sure the LONE PAIR is included

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35
Q

How do you name aromatic compounds?

A

Cyclo-

eg. 3-methylcyclohexanol

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36
Q

When talking about oxidation of alcohols to aldehydes, what should you write instead of heat?

A

Distillation

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37
Q

What is a property of cyclohexane?

A

It is weakly acidic

38
Q

When asked to analyse H NMR what must you do?

A

Write out the information fully, describing where on the spectrum the peak is, whether it is a singlet etc. , how many hydrogens it has and what structure each peak represents eg. CH3

39
Q

What is the bonding and shape of H2O

A

H2O has two bonded pairs and 2 lone pairs so it forms a tetrahedral structure shape which is nonlinear with 104.5 degrees

40
Q

What can you work out from the amount of optical isomers there are?

A

The amount of chiral centres

eg. 4 optical isomers = two chiral centres

41
Q

What happens when a carboxylic acid reacts with magnesium?

A

Magnesium is a group two metal so it will put brackets and 2 around the COO- part

42
Q

What factors affect retention time?

A

Solubility- more soluble will spend more time dissolved in the stationary phase
Boiling point- higher boiling point means it will spend longer condensed in the tube
Temperature of gas chromatography equipment- hotter means more time evaporated

43
Q

How does gas chromatography separate the compounds in the mixture?

A

Solubility

44
Q

What is M+?

A

Molecular ion

45
Q

What is easy to forget when reducing aldehydes?

A

The carbon that is already in the aldehyde

46
Q

In electrophilic substitution of phenol, what are the products?

A

Hydrogen ions from the ring, which will join up with compounds like Br to make HBr

47
Q

What is the difference between bonding in kekules structure and benzene?

A

P orbitals overlap in the double bond
The pi bonds/electrons are localised in the double bond
The pi bonds/electrons are delocalised in the pi system

48
Q

What are the reagents for turning NH2 into N+?

A

HNO2

49
Q

What is there to remember if NH2 is anywhere to be seen?

A

If acid is involved, it will change to NH3+!

50
Q

What can amino acid type structures form if they dont form condensation polymers?

A

Rings

They can form them with just one monomer or two

51
Q

What is a use for NMR spectroscopy in medicine?

A

Magnetic resonance imaging

Body scanners

52
Q

What region of the electromagnetic spectrum is used in H NMR spectroscopy?

A

Radio waves

53
Q

In electrophilic substitution, what can the electrophile be?

A

Br-Br

54
Q

When converting nitrophenol (NO2) to aminophenol (NH2), what is the reaction?

A

Nitrophenol + 6[H] —–> aminophenol + 2H2O

55
Q

How is an aminophenol (NH2) able to react with an acid?

A

The lone pair on the nitrogen can accept a proton

56
Q

What is a condensation polymer?

A

WHere monomers are joined together and a small molecule is lost such as H2O

57
Q

When talking about oxidation, what must you always say?

A

Orange to green colour change

58
Q

What can molecules with functional groups on both ends do?

A

Form a ring

59
Q

What does it mean when it says a peptide bond?

A

An amide bond, not an ester bond

60
Q

In terms of isoelectric point, what can they get you to draw?

A

The zwitterion and an amino acid in an alkali or acidic state
NH3+ or COO-

61
Q

What are benefits of using single stereoisomers in the synthesis of drugs?

A

No side effects

Stops the need to separate out the stereoisomers (cost)

62
Q

Whenever you see hydrolysis of ester/amide bonds, what must you do?

A

Look for whether it is acid or base hydrolysis
Acid = NH3+
Base = COO-Na+

63
Q

How can products be identified from gas chromatography and mass spectrometry?

A

Volatile compounds are separated

They are compared with a spectral database

64
Q

Why is TMS used in NMR spectroscopy?

A

Because it is the standard

It is 0 ppm

65
Q

When analysing H NMR, what should you do to show all your reasoning?

A

Make a table of all the information you know
Connect each environment to the functional group part of the molecule
Then add together the environments you know go together

66
Q

What can cause an increase in risk of suffering from heart disease?

A

A trans unsaturated fatty acid

Increases the amount of bad cholesterol

67
Q

When naming organic molecules of benzene rings, how do you know what number to give them?

A

1 is always on OH

Don’t miss out on that 1 and make everything one less!

68
Q

What is the process by which TLC separates amino acids?

A

Adsorption

69
Q

What type of reaction is reduction of aldehydes?

A

Nucleophilic addition

70
Q

How might a polyester be degraded?

A

Photodegradable
Hydrolysis
Biodegradable

71
Q

In zwitterions, what happens if there are other NH3 groups on it?

A

It is still only the one COOH and NH3 that swap Hs

72
Q

Why might zwitterions have different isoelectric points?

A

Because an amino acid has another NH3 group on it which will mean its isoelectric point is a higher pH/above 7

73
Q

What should you look out for when counting chiral centres?

A

Centres with the same group on them eg two CH3 groups look like sticks in skeletal

74
Q

What does it mean if it is a natural steroid?

A

It produces only one optical isomer

75
Q

How can results from gas chromatography predict compounds and their relative proportions?

A

Measure retention times
Compare them to a spectral database
Calculate the are under the peaks for relative proportions

76
Q

What explains the shape of molecules?

A

Bonding pairs repeleg. in tetrahedral, 4 bonding pairs repel

77
Q

Why are cyclo/aliphatic compounds used in fuels?

A

Because they have more efficient burning

78
Q

What are the termination steps in free radical substitution>

A

2Br to Br2
C6H11 + Br to C6H11Br
C6H11 + C6H11 to C12H22

79
Q

What is the small product of electrophilic addition with Br2?

A

HBr

80
Q

How are esters named?

A

First part is the part that is after the O

81
Q

How is CO2 stored?

A

By reacting with metal oxides (GROUP 2)

In the sea

82
Q

What is the reaction in catalytic converters?

A

2NO + 2CO —-> 2CO2 + N2

83
Q

What is the definition of structural isomers?

A

Same molecular formula but different structural formula

84
Q

What are the products when making an ester?

A

Ester and H2O

85
Q

What is it easy to forget when comparing things about different compounds?

A

To actually compare them!

86
Q

Why is D used in NMR instead of H?

A

Doesn’t absorb

Doesn’t give a peak

87
Q

Why are some artificial sweeteners not used any more?

A

Adverse side effects

88
Q

What is the difference in enthalpy change of hydrogenation between Kekule’s structure and benzene?

A

The enthalpy change of hydrogenation is less exothermic

89
Q

What is meant by retention time?

A

The amount of time the compound takes to exit the column

90
Q

What is the structure of a tryglyceride?

A

The three carbons, then the Os, then the C=O group

91
Q

How can the problems of producing two optical isomers be overcome?

A

With bacteria
With chiral synthesis
By using natural chiral molecules

92
Q

What is meant by an alpha amino acid?

A

Both the NH2 and the COOH are joined to the same carbon

A Level (25 decks)

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