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Edexcel Chemistry A level > Organic (2) > Flashcards

Organic (2) Flashcards

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1
Q

Functional group of nitriles

A

CN

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2
Q

Give the functional groups of 2 derivates of Carboxylic acids

A
  • esters: COO
  • Acyl Chlorides - COOCl
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3
Q

Functional group of amides

A
  • NH2
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4
Q

define structural isomer

A
  • same molecular formula, diff structural formula.
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5
Q

position isomer

A

same molecular formula, but diff position of functional groups

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6
Q

Functional group isomers, give an example.

A

same molecular formula, but arrange to give diff functional groups. eg alcohol to ether.

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7
Q

where is the COO in aldehydes?

A

end

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8
Q

where is the COO in ketones?

A

middle.

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9
Q

stereoisomerism

A
  • same structural formula, diff arrangement of atoms in space.
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10
Q

Optical isomerism components (what is needed for it to happen?)

A
  • 4 diff groups need to be attached to a carbon (an asymmetric carbon)
  • four groups arranged tetrahedrally around the C.
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11
Q

enantiomers

A
  • 2 compounds that are optical isomers of each other.
  • are nonsuperimposable.
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12
Q

give some properties of optical isomers

A
  • can rotate plane polarised light
  • similar chemical and physical properties.
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13
Q

define a racemic mixture

A
  • a mixture containing 50/50 of enantiomers.
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14
Q

Give 1 property of a racemic mixture

A
  • will not rotate plane polarised light.
  • because one will rotate clockwise, and one anticlockwise, so will cancel out.
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15
Q

why is trying to separate a racemic mixture extremely difficult?

A
  • very expensive
  • same chemical and physical properties.
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16
Q

how do you form a racemate? (mechanism wise)

A
  • forms when a trigonal planar reactant or intermediate is approached by 2 species attacking from either side.
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17
Q

Which type of mechanism can actually form a racemate?

A
  • Sn1 only (happens in 2 steps)
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18
Q

Describe the Sn1 mechanism to form a racemate.

A
  • any species attached to Carbon breaks off, forming a carbocation intermediate.
  • this is planar
  • 2 species can now either attack from the top or bottom, resulting in diff enantiomers forming.
  • can tell when it is a racemate, as will no longer rotate plane-polarised light.
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19
Q

Describe the Sn2 mechanism

A
  • species attacks the carbon (slightly positive) and then jumps off to another delta negative species, breaking it off
  • forms a transition stage.
  • cannot form racemic mixture, only forms one enantiomer. (so will still rotate plane polarised light)
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20
Q

what two types of reactions can form a racemate?

A
  • nucleophilic addition, and electrophilic addition.
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21
Q

describe and explain the trend in solubility of carbonyls in water

A
  • smaller the carbonyl, the more soluble in water it is.
  • because it can form H bonds with water.
  • pure carbonyls cannot form hydrogen bonds, but can bond by forming permanent dipole-dipoles.
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22
Q

describe the reaction, reagent and conditions and observations of the oxidation of aldehydes

A

Reaction: aldehyde—> carboxylic acid
Reagent: acidified K2Cr2O7 (with H2SO4)
conditions: heat under reflux.
observations: orange to green, as the Cr2O72- ion is reduced to the Cr3+ ion.

23
Q

Give the conditions and test for aldehydes

A
  • tollens reagent, heat gently (eg with water bath)
  • will form a silver mirror.
24
Q

Give another test and conditions for aldehydes

A
  • Fehling’s solution, heat gently (eg with water bath)
  • blue to brick red.
25
Q

describe the reaction, reagent and conditions and observations of the reduction of carbonyls.

A

reaction: carbonyl —> alcohol (primary for aldehydes, secondary for ketones)
reagent: NaBH4 (sodium tetrahydroborate) in dry ether.
conditions: room temp and pressure

26
Q

describe the reaction, reagent and conditions, observations and mechanism of HCN to a carbonyl.

A

reaction: carbonyl —> hydroxynitrile
Reagent: HCN in the presence of KCN
Conditions: room temp and pressure
Mechanism: nucleophilic addition.

27
Q

describe the reaction, reagent and conditions, observations and mechanism of the reaction between iodine and a carbonyls.

A

reaction: forms a salt and CHI3
reagent: iodine and NaOH
conditions: warm very gently
Observations: yellow ppt and antiseptic smell.

28
Q

Describe the test of 2,4DNP with carbonyls.
How can you further identify it?

A
  • reagent: 2,4 DNP
  • result: orange ppt in presence of carbonyl group.
  • can use the melting point of the crystal formed to help identify which carbonyl was used, compare values to known values in a database.
29
Q

why are carboxylic acids soluble in water?

A
  • can form H bonds with water.
30
Q

How are Carboxylic acid salts stabalised?

A
  • by delocalisation, makes dissociation more likely.
31
Q

Name 4 methods to prepare carboxylic acids.

A
  • full oxidation of primary alcohols
  • oxidation of aldehydes
  • Hydrolysis of nitriles
  • waterand acyl chloride
32
Q

describe the reaction, reagent and conditions, observations and mechanism of full oxidation of primary alcohols

A
  • forms carboxylic acid
  • reagent: acidifed (with H2SO4) Pottasium Dichromate.
  • conditions: heat under reflux, excess of dichromate, distill off product once reaction is finished.
32
Q

describe the reaction, reagent and conditions, observations and mechanism of reduction of carboxylic acids

A
  • forms alcohol
  • reagent: LiAlH4 in dry ether (reducing agent)
  • conditions: RTP
32
Q

Name a functional group test for carboxylic acids

A
  • react acid with solid sodium carbonate or aq sodium hyrdogen carbonate.
  • effervescence produced, CO2 produced.
33
Q

Which is the only acid that can’t be oxidised by an oxidising agent? why? what does it form instead?

A
  • methanoic acid
  • effectively has an aldehyde group
  • forms carbonic acid, which decomposes to give CO2
34
Q

describe the reaction, reagent and conditions, observations and mechanism of the reaction between carboxylic acids and PCl5

A
  • forms acyl chloride
  • reagent: PCl5
  • conditions: room temp
    -observations: white steamy fumes HCl.
35
Q

How do you name esters?

A

-yl bit comes from alcohol
-anoate bit comes from carboxylic acid.

36
Q

How to you form esters?

A
  • alcohol and carboxylic acid react together
  • need acid catalyst, as it is a reversible reaction.
37
Q

Name 3 uses for esters

A
  • food flavourings, perfumes, solvents for organic polar substances.
38
Q

Why do esters not form H bonds?

A
  • no hydrogen in an ester is bonded to a highly electronegative atom.
39
Q

Name 2 ways in which esters can be hydrolysed.
give some details.

A
  • with NaOH - complete
  • with dilute HCl- reversible
    both are heated under reflux.
40
Q

What properties do esters need to have in order to be used in perfumes.

A
  • non toxic
  • soluble in solvent like ethanol
  • volatile
  • not react with water.
41
Q

give some properties of acyl chlorides
give reasons.

A
  • highly reactive (more reactive than carboxylic acids) due to its double dipole (C=O and C-Cl)
  • Cl group classed as a good leaving
42
Q

describe the reaction, reagent and conditions, observations and mechanism of acyl chlorides with water

A
  • reagent: water
  • forms carboxylic acid.
  • conditions: room temp.
  • white steamy fumes of HCl given off.
43
Q

describe the reaction, reagent and conditions, observations and mechanism of acyl chlorides with ammonia.

A

reagent: ammonia
- forms primary amide
- conditions: room temp.
- white SMOKE of NH4Cl given off.

44
Q

describe the reaction, reagent and conditions, observations and mechanism of a acyl chloride with a primary amine

A
  • reagent: primary amine
  • forms secondary amide
  • conditions: room temp
45
Q

describe the reaction, reagent and conditions, observations and mechanism of acyl chlorides with alcohol.

what are the advantages of this reaction?

A
  • reagent: alcohol
  • forms an ester
  • conditions: room temp.
  • observations: white steamy fumes of HCl given off.

advantages:
- not reversible, so has a higher yield
- much quicker
- no high temp needed, so saves on energy costs.

46
Q

what is the product formed when esters are hydrolysed with dilute acid.
What are the conditions needed for this reaction?
Any other info?

A
  • forms alcohol and carboxylic acid
  • heat under reflux
  • is reversible
47
Q

what is the product formed when esters are hydrolysed with NaOH?
What are the conditions needed for this reaction?
Any other info?

A
  • forms salt and alcohol
  • heat under reflux.
  • is non reversible.
48
Q

describe the reaction, reagent and conditions, observations of acyl chlorides with water

A
  • forms a carboxylic acid
  • reagent: water
  • conditions: room temp.
  • observation: white steamy fumes of HCl given off
49
Q

what will a polyester hydrolyse to give (with HCl)

A
  • diol and dicarboxylic acid
50
Q

what will a polyester hydrolyse to give (with NaOH)

A
  • diol and diacyl chloride salt.
51
Q
A

Edexcel Chemistry A level (18 decks)

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