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Chemistry A-Level > WM1, 2 > Flashcards

WM1, 2 Flashcards

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1
Q

describe the polarity of an alcohol molecule

A

due to the polarised O-H bond due to the hydrogen bonding
- hydrogen bonds are between the oxygen on one molecule and the hydrogen (in an OH) in another molecule
- permanent dipole, hydrogen is positive and oxygen is negative

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2
Q

describe and explain the boiling points of alcohols in comparison to the corresponding alkanes of similar Mr

A
  • alcohols have higher boiling points than alkanes of similar molecular mass
  • this is because alcohols contain induced dipole-dipole forces and hydrogen bonds (which are stronger), whilst alkanes only contain induced dipole-dipole forces
    -when liquid boils, these forces must be broken to form a gas
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3
Q

describe the solubility of alcohols

A

the hydrogen bonding between alcohol and water molecules allows the molecules to mix together
as the hydrocarbon chain becomes longer, the molecule becomes larger and the influence of the -OH group decreases.
So solubility decreases going down the group

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4
Q

what is a primary, secondary and tertiary alcohol

A

Primary- the -OH is bonded to a carbona tom that is bonded to ONE other carbon atom
Secondary- the -OH is bonded to a carbona tom that is bonded to two other carbon atoms
Tertiary- the -OH is bonded to a carbon atom that is bonded to three other crabon atoms

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5
Q

state the name and chemical formula for the oxidising agent used in the oxidation of alcohols

A
  • acidified potassium dichromate (VI)
  • K2Cr2O7
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6
Q

describe what happens to the ions of the oxidising agent when oxidising an alcohol (and the colours at each stage)

A

It starts off with the dichromate ion Cr2O7 ^2- (orange)
which then get reduced to green chromate (III) ions Cr3+

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7
Q

what happens to the -OH group of an alcohol when oxidised

A

it is converted into a carbonyl group C=O

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8
Q

describe how you would produce an aldehyde from an alcohol

A

you would need to oxidise a primary alcohol
Set up distillation equipment with heat source, conical flask, condenser, and a beaker
gently heat the alcohol in excess (to increase the chances of it not being further oxidised) mixed with acidified potassium dichromate(VI), and since the aldehyde has a lower boiling point than the alcohol, it will form gas first and be condensed into beaker

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9
Q

describe how you would produce a ketone from an alcohol

A

-you would need to oxidise a secondary alcohol
- place the secondary alcohol and acidified potassium dichromate (VI) into a pear shaped flask and add anti bumping granules
- heat until fully reacted

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10
Q

why do we reflux?

A

It is a safe method for heating reactions involving volatile and flammable liquids

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11
Q

what is the difference between the C=O (carbonyl) group in an aldehyde and and a ketone

A
  • in an aldehyde, the carbonyl group is at the end of the alkane chain
  • in a ketone, the carbonyl group is in the middle of an alkane chain
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12
Q

when alcohols lose a molecule of water what do they form

A

an alkene

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13
Q

what are the conditions needed for the dehydration of alcohols

A
  • a heated catalyst of alumina Al2O3
  • 300 degrees celsius
  • with concentrated sulfuric acid
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14
Q

what type of reaction is the dehydration of alcohols

A

elimination reaction

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15
Q

how do you produce a haloalkane from an alcohol
- what needs to react
- what are the conditions needed
- what type of reaction is it

A
  • an alcohol and and a halide ion
  • must be in the presence of a strong acid
    e.g H+ and Br-
  • it is nucleophilic substitution
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16
Q

what is it called when an alcohol reacts with a carboxylic acid

A

esterification

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17
Q
  • what do you produce when you react
    ethanol + ethanoic acid
A

—> ethyl ethanoate

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18
Q

describe the process of making ethyl ethanoate

A
  • you would react ethanol and ethanoic acid using a strong acid catalyst, this can be done by adding a small amount of concentrated sulfuric OR hydrochloric acid
  • reaction is heated under reflux
  • when the reaction state is in equilibrium the ester should be separated from the solution by distillation and purified
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19
Q

what are the two ways of converting alcohols into esters

A
  • esterification using an acid anhydride
  • esterification using a carboxylic acid
20
Q

describe how to name an ester produced by an alcohol and carboxylic acid

A
  • use the prefix of the alcohol it is derived from and add “yl”, e.g. methyl, ethyl etc.
  • use the prefix of the carboxylic acid that it is derived from and add “anoate”
21
Q

describe the process of forming an ester from an acid anhydride

A
  • react an acid anhydride with an alcohol to produce an ester
  • reacts with an alcohol completely on warming to give a much higher yield of ester
  • since they are much more reactive than carboxylic acids
22
Q

what are alcohols structural isomers with 1

A

ethers

23
Q

how do you produce an ether from an alkane

A
  • when you substitute an alkoxy group (singularly bonded oxygen) for a hydrogen atom
24
Q

how do you name an ether

A
  • the longer hydrocarbon chain is chosen as the parent alkane
  • other chain is looked at like an alkyl group e.g. methoxy pentane
  • longer carbon chain is 5C, shorter is 1C
25
Q

what are the main techniques of purification and what needs to be purified and why

A
  • separating funnel, use of drying agents, and simple distillation
  • because during synthesis only crude products are produced, which need to be purified before they are used
26
Q

what happens when salicylic acids react with alcohols

A
  • an ester is produced
27
Q

how do you test for salicylic acid

A
  • a neutral solution of iron (III) chloride turns pink
28
Q

where are the three environments that and hydroxyl group can occur

A
  • as a part of a carboxyl group in a carboxylic acid
  • attached to an alkane chain in alcohols,
  • attached to a benzene ring in phenols
29
Q

how does water behave as a weak acid

A
  • water dissociates to a very small extent
  • at any given point in time a small amount of water molecules donates H+ ions to other water molecules
30
Q

what is the reaction of an OH group with water

A

R-OH + H2O === R-O- + H3O+
equilibrium sign

31
Q

how do you test for carboxylic acid

A
  • you react the substance with sodium carbonate and the solution should fizz
32
Q

how do you test for an aldehyde, and explain

A
  • you add acidified potassium dichromate, and it should turn from orange to green because it is further oxidising it to become a carboxylic acid
33
Q

what part of the acid anhydride is added to alcohol when you react them together

A
  • one half of the molecule including the oxygen that it is doubly bonded to and NOT the single bonded oxygen
34
Q

what is pentyl propanoate and what were the reactants

A
  • pentyl propanoate is an ester
  • reactants are pentanol and propanoic acid
35
Q
  • name the molecule, and the alcohol and carboxylic acid it derives from
    C4H9–O–(CO)–CH3
A
  • butyl ethanoate
  • butanol and ethanoic acid
36
Q

what is a carboxyl group

A

-COOH

37
Q

what is the reaction that shows water behaving as a weak acid

A

H-OH + H2O === H-O- + H3O-

38
Q
  • compare the reactions of
    1. ethanol + water
    2. water + water
    3. phenol + water
    in terms of them being acidic
A

R-OH + H2O === R-O- + H3O-
1. ethanol is a weak acid and donates less of it’s H+ ions so the equilibrium lies further to the left
2. water acts a weak acid, donates some H+ ions to the other water molecule
3. stronger acid, donates more H+ ions and the equilibrium lies further to the right

38
Q

what reacts with strong bases?
give an example of a strong base and what is the main product

A
  • phenols and carboxylic acids can react with strong bases e.g. NaOH
  • to form salts
39
Q

describes the salts produced between strong bases and acids

A
  • the salts are ionic and remain in the solution after the reaction
40
Q

what complex forms in a positive test for iron (III) chloride

A
  • the C=C-OH (the enol group) forms a purple complex with Fe3+ ions in neutral solution
41
Q

what is another name for salicylic acid and what is the structure of salicylic acid

A
  • benzene ring
  • COOH attaches to one of the carbons
  • OH attached to the following carbon
42
Q

phenol + acid anhydride

A

phenyl (A.A prefix) anoate + (A.A prefix) oic acid

43
Q

what are the two ways of esterifying salicylic acid, what are the products if each

A
  • the phenol OH group can react with an acid anhydride (forms aspirin)
    -the COOH group can react with an alcohol (oil wintergreen)
44
Q

why can aspirin be absorbed into the blood stream through the stomach wall

A
  • because it is soluble in water
45
Q

what are the differences between oil wintergreen and aspirin

A

ASPIRIN
1. soluble in water
2. absorbed into the blood stream through stomach wall
3. reduces pain and swelling

OIL WINTERGREEN
1. soluble in fats
2. absorbed through the skin
3. reduces pain and swelling

Chemistry A-Level (26 decks)

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