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A-level chemistry unit 6 > unit 6 section 1 isomerism and carbonyl compounds > Flashcards

unit 6 section 1 isomerism and carbonyl compounds Flashcards

1
Q

what is a stereoisomer

A

they have the same structural formula, but their atoms are arranged differently in space.

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2
Q

what is a chiral carbon

A

a chiral carbon atom is a carbon atom that has four different groups/functional groups attached to it

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3
Q

what is an optical isomer

A

it is a type of stereoisomer that has a chiral carbon atom in it

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4
Q

what is it called when a chiral carbon atom functional group is arranged in a different way forming a different molecule ( kind of like a mirror image )

A

they are called enantiomers or optical isomers

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5
Q

what does superimposed mean

A

it means that no matter which way the molecule turned/arranged , it doesnt have and optical isomer

-enantiomers are not superimposed

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6
Q

how do you draw an optical isomer

A

-locate the chiral carbon atom
-draw the molecule in 3D
-then draw the isomer

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7
Q

are optical isomers optically active

A

yes- they rotate plane polarised light

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8
Q

what is a molecule that can be superimposed

A

achiral

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9
Q

what is plane polarised light

A

it is light that has passed through a polarising filter, this means that the light is vibrating in the same plane ( up or down, side to side)
- normal light vibrates in all directions.

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10
Q

how is plane polarised light rotated

A

when you pass plane polarised light through a optically active mixture, the molecule interacts with the light and rotates the plane of vibration of the light.
- the two enantiomers will rotate the plane polarised light in opposite directions ( clockwise and anticlockwise )

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11
Q

what is a racemate

A

it is a mixture that contains equal quantities of each enantiomer of a optically active compound

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12
Q

do racemates show any optical activity

A

no as the two enantiomers cancel out each others light rotating effect

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13
Q

what reagent is mainly used to reduce aldehydes and ketones

A

NaBH4 ( sodium borohydride ) , however in equations [H] is used to represent the hydrogen from it

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14
Q

what are hydroxynitriles

A

they are contain hydroxyl group (OH-) and nitrile groups (CN)

when naming them the nitrile group is more important, so you use nitrile at the end and hydroxy at the start for the alcohol

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15
Q

how to form a hydroxynitrile

A

they can be formed by reacting either a aldehyde or ketone with potassium cyanide(KCN) followed by a dilute acid.

you can also make it by reacting a ketone or aldehyde with hydrogen cyanide

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16
Q

explain why carboxylic acids dissociate

A

this is because carboxylic acids are weak acids, in water they partially dissociate in water to form a carboxylate ion and a H+ ion ( the H+ is removed from the OH of the carboxylic acid

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17
Q

how does an esterification reaction occur

A

this happens when you react a carboxylic acid with an alcohol in the presence of a strong catalyst, an ester is formed. this is called an esterification reaction

the catalyst could be sulfuric acid (H2SO4) or HCL or H3PO4

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18
Q

how do you name an ester

A

first you look at the part that came from the alcohol, the alkyl group and name that first and then name the carboxylic acid and replace the -oic acid with -oate

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19
Q

what are the useful properties of esters

A
  • esters have a sweet smell, they can be used in perfumes.
  • they are polar liquids, this means that they can dissolve polar compounds. they have low boiling points and evaporate easily from mixtures. they make good solvents in glues and printing inks
  • they are used as plasticers, they are added to plastics during polymerisation to make them more flexible
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20
Q

what are the two types of hydrolysis of esters

A

acid hydrolysis and base hydrolysis

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21
Q

explain what happens in an acid hydrolysis reaction

A

the ester is split into an acid and alcohol.this happens when you react the ester with water and then reflux the ester with dilute acid, such as hydrochloric or sulfuric acid

22
Q

explain what happens in a base hydrolysis reaction

A

the ester is split into carboxylate ion and alcohol. this happens when you react the ester with OH- ions from a dilute alkali under reflux

23
Q

what are animal fats and vegetables oils

A

they are esters of glycerol and fatty acids

24
Q

explain the facts and properties of fats

A

fats have mainly saturated hydrocarbon chains, and they fit neatly together which increases the van der waals forces between them. this means that they are solid at room temperature and require higher temperatures to melt them.

25
Q

explain the facts and the properties of oils

A

they have unsaturated hydrocarbon chains. the double bonds means that the chains dont bend and do not pack well together. this decreases the effect of the van der waals forces meaning that they are easier to melt and are not solid at room temperature.

26
Q

how do you hydrolyse fats and oils

A

you heat them up with sodium hydroxide
the OH- ions react with the fats and the oils forming carboxylate ion and a alcohol ( glycerol ) , then the carboxylate reacts with the Na+ to form a sodium salt ( which is a soap )

27
Q

how do you reverse the hydroylsis of fatty acids

A

this is done by adding HCL. the H+ ion from the Hcl replaces the Na from the carboxylate ion.

28
Q

how do you convert vegetable oils into biodiesel

A

This is done by reacting the vegetable oils with methanol under a strong alkali catalyst such as potassium hydroxide or sodium hydroxide. this forms a mixture of methyl esters of long chain fatty acids

29
Q

is biodiesel 100% carbon neutral

A

the crops absorb the same amount of CO2 as they produce when they are burned. however energy is used to make the fertizers which if they are made using energy from fossils fuels then overall it is not carbon neutral

30
Q

what is the functional group of acyl chloride

A

COCL

31
Q

what generally happens when an acyl chloride group reacts with a molecule

A

the CL is substituted by an oxygen or nitrogen group and misty fumes of hydrogen chloride are given off.

32
Q

explain the reaction of acyl chlorides and water

A

they react vigorously with cold water and producing a carboxylic acid.

33
Q

explain the reaction of acyl chlorides and alcohols

A

they react vigorously with alcohols at room temperature producing an ester.

this is a faster method of producing an ester than esterification

34
Q

explain the reaction of acyl chlorides and ammoina

A

they react vigorously with ammonia at room temperature to form amides

35
Q

explain the reaction of acyl chlorides with primary amines

A

they react vigorously with primary amines at room temperature to produce N -substituted amides

36
Q

what type of reaction occurs when you react acyl chloride and what are the steps

A

nucleophilic addition-elimination reaction
1- he nucleophile adds onto the acyl chloride, displacing a CL- ion
2-the hydrogen leaves to create an acyl chloride derivative

37
Q

what is an acid anhydride made from

A

they are made from two identical carboxylic acids. they are joined by an oxygen between the two carboxylic acid molecules. the oxygen has come from one of the OH groups from the carboxylic acid molecule and from one hydrogen from the other molecule, it is released as water.

38
Q

how do you names acid anhydrides

A

if you know the name of the carboxylic acid, you remove the acid from the name and replace it with anhydride
e.g butanioc acid - butanioc anhydride

39
Q

what happens when you react an acid anhydride with water

A

you form a carboxylic acid

40
Q

what happens when you react acid anhydrides with alcohols

A

you form an ester and carboxylic acid

41
Q

what happens when you react an acid anhydride with ammonia

A

you form an amide and you also make a carboxylic acid

42
Q

what happens when you react an acid anhydride with an amine

A

you produce an n-substituted amide and a carboxylic acid

43
Q

how is aspirin manufactured

A

it is manufactured by by reacting salicylic acid ( has and alcohol group ) with either ethanoic anhydride or ethanoyl chloride

44
Q

why is ethanoic anhydride used in industry rather than ethanoyl chloride in the production of aspirin

A

ehanoic anhydride is used because it is cheaper than ethanoyl chloride and it is also safer than ethanoyl as it is less corrosive, reacts slowly with water and doesn’t produce dangerous hydrogen chloride fumes.

45
Q

why can aldehydes be easily oxidised to carboxylic acids

A

this is because there is a hydrogen attached to the carbonyl group

46
Q

what tests can be used to distinguish between an aldehyde and a ketone and what are the positive results

A

tollens - aldehyde - silver mirror ( ketone no change )
felhings - aldehyde - blue solution to brick red precipitate ( ketone no change )

47
Q

what type of reaction occurs when aldehydes and ketones are reduced back to alcohols

A

nueclophilic addition reactions

48
Q

what is formed when you react a carboxylic acid with a carbonate compound ( e.g. NaCo3 sodium carbonate )

A

it forms a salt, carbon dioxide and water

49
Q

how can you speed up the process of hydrolysising an ester

A

instead of just using water use a acid or alkali

50
Q

what type of reactions occur with acyl chlorides

A

they are all nucleophillic addition-elimination reactions

A-level chemistry unit 6 (5 decks)

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