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Chemistry > A2 Organic > Flashcards

A2 Organic Flashcards

1
Q

What are the 2 reagents often used for reduction

A

LiAlH4 in ether (stronger than NaBH4)

NaBH4

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2
Q

Name the mechanism that turns aldehyde/ketones back to alcohols

What are the conditions

A

Nucleophilic addition

Room temp and pressure

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3
Q

What’s another way carbonyls can be reduced apart from nucleophilic addition

What are the conditions

A

Catalytic hydrogenation

H2/Ni catalyst
High pressure

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4
Q

What’s the reaction, reagent and condition for carbonyl -> hydroxynitrile

A

KCN , dilute H2SO4

Room temp and pressure

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5
Q

What is used to show the presence of C=O group

What’s the name of this reaction

A

2,4-dinitrophenylhydrazine

Nucleophilic addition elimination

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6
Q

What’s the result of adding dinitrophenylhydrazine to c=o groups

A

Bright orange / yellow ppt forms

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7
Q

What reagent and condition is needed in esterification

A

CONCENTRATED H2SO4

Heating under reflux

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8
Q

Why is esterification not preferred

A

It is a reversible reaction, which is quite slow and produces low yield

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9
Q

State a few uses of Ester

A

Perfumes and flavourings because of its sweet smell

Solvents for polar organic substances

Plasticisers for polymers

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10
Q

What is the name of reaction when esters -> alcohol and carboxylic acid

What reagents and condition is needed

A

Acid hydrolysis

H2O
Dilute HCL

heat under reflux

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11
Q

What does a base hydrolysis form

What’s the condition and reagent

A

Carboxylate ion (salt) and alcohol

NaOH
Heat under reflux

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12
Q

What’s the difference between acid and base hydrolysis and which one is better

A

Base hydrolysis is NOT reversible and so it produces a much higher yield

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13
Q

What is biodiesel

A

A mixture of methyl esters of long chain carboxylic acids

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14
Q

Is biodiesel carbon neutral

A

Can be thought of as carbon neutral because when crops absorb the same amount of co2 as they produce when burned
But
Energy is used in making fertilisers to grow crops, and used in planting, harvesting etc
Also if energy comes from burning fossil fuels then its not carbon neutral

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15
Q

What can acyl chloride react with and what are the products

What’s the name of this mechanism

A

Water - carboxylic acid and Hcl
Ammonia - amide and Hcl
Alcohol - Ester and Hcl
Primary amine - amide and Hcl

Nucleophilic addition elimination

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16
Q

What can acid anhydrides react with
What are the products
What’s the name of reaction

A

Water - carboxylic acid x2
Ammonia - amide and cooh
Alcohol - Ester and cooh
Primary amine - amide and cooh

Nucleophilic addition elimination

17
Q

What are the conditions of both acyl chloride and acid anhydride reactions

A

Room temp

18
Q

What’s an alternative method of producing esters

Why’s this better

A

Reacting acyl chloride with alcohol

Produces much higher yield

19
Q

Observations from acyl chloride reactions

A

Steamy white fumes of HCL

20
Q

What is delocalised energy

A

Extra stability in benzene molecule due to electron delocalisation

21
Q

Evidence that led scientists to doubt kekule’s theory

A
  1. Bond length is different between C=C (short) and C-C (long)
  2. Enthalpy change of hydrogenation is less exothermic than expected when compared to that for cyclohexane
  3. Only reacts with Br2 at high temp/presence of halogen carrier
22
Q

Why is benzene more stable than cyclohexane-1,3,5-triene

A

Electrons are stabilised

23
Q

Why wouldn’t benzene undergo addition reactions

A

It would involve breaking up the delocalised system

24
Q

What’s the toxicity of benzene

What is less toxic, why?

A

Carcinogen (cancer causing molecule)

Methylbenzene is less toxic and reacts more readily because the methyl group releases electrons into the delocalised system making it more attractive to electrophiles

25
Q

Reagents , conditions and mechanism for nitration

A

Electrophilic substitution
Conc H2SO4 and HNO3
Done at ~60degrees. Of higher temp is used, a second nitro group can be substituted

26
Q

State the change in functional group in fried elf crafts acyl action

State the reagents conditions and mechanism for this

A

Benzene to phenyl ketone
Reagents : acyl chloride with anhydrous AlCL3 catalyst
Conditions : heat under reflux (50degrees)
Mechanism: electrophilic substitution

27
Q

What’s the mechanism for nitroarene-> phenylamine

Reagent?
Condition?

A

Reduction reaction
Sn + Hcl or Fe + Hcl
Conditions : heating

28
Q

What does delocalisation do to a phenol

A

Makes C-O bond stronger and O-H bond weaker

Thus it is more acidic cuz it’s more likely to give away proton

29
Q

What does delocalisation do to phenylamine

A

Less basic than chained amines as the lone pair is delocalised onto the ring, making it less available to accept proton

30
Q

What forms when amine reacts with acid
CH3NH2 + H+ ->

What could you add to convert it back

A

Ammonium salt CH3NH3+

Arden NaOH to convert it back

31
Q

In this reaction
CH3CH2Br + NH3 -> CH3CH2NH3+ +Br-
CH3CH2NH3+ + NH3 -> CH3CH2NH2 + NH4Br
Why should excess ammonia be used

A

It can limit the further subsequent reactions and will maximise the amount of primary amine formed

32
Q

What can quaternary salts be used as?

And what does that do?

A

Cationic surfactants

Surfactants reduce the surface tension of liquids.
Helps in their uses as fabric softener, hair conditioner etc

33
Q

Reactants for halogenoalkane to amine (heat under reflux)

A

Haloalkane to nitrile - KCN in ethanol (heat under reflux)

Nitrile to amine - LiAlH4 in ether with Ni catalyst

34
Q

What’s the disadvantage of the reaction of producing amine from haloalkane

A

It is 2 stepped thus low yield

KCN is toxic

35
Q

Reagent condition and mechanism for nitrobenzene-> phenylamine

A

Reagent : Sn and Hcl
Condition: heating
Reduction

Chemistry (12 decks)

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