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Chemistry > Organic Part 2 > Flashcards

Organic Part 2 Flashcards

1
Q

Define Nucleophile

A

Species that donates a pair of electrons

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2
Q

Define Electrophile

A

Species that accepts a pair of electrons

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3
Q

What occurs during nucleophilic substitution?

A

Nucleophile attacks a polar molecule and removes a functional group

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4
Q

When does nucleophilic substitution occur?

A

Water is the solvent
Low temp
Less haloalkane branching

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5
Q

What are the reagents of nucleophilic substitution?

What do they produce?

A

Potassium hydroxide - alcohols

Hot ethanolic acid of Na/K cyanide - nitriles

Excess ammonia - amines

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6
Q

What happens if a nitrile is hydrolysed?

What does the production of nitrile do to the Carbon chain?

A

Carboxylic acid produced

Increase its length

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7
Q

Why can further substitution of methyl amine occur?

How can this be prevented?

A

It has a lone pair on the nitrogen atom

Use excess ammonia

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8
Q

Describe and explain reactivity, boiling point and vdw trend of halogenoalkanes

A

C - halogen bond strength (enthalpy) decides reactivity
Bond enthalpy decreases down group
C - I bond easiest to break so most reactive

BP increase down group
Vdw decreases down group

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9
Q

When does elimination occur?

A

Ethanol is used as a solvent
High temperature
A lot of branching of haloalkane

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10
Q

Why is ozone beneficial?

A

Absorbs ultra violet radiation

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11
Q

Why are CFCs useful?

Examples of uses

A

Very unreactive

Short chain - aerosols
Long chain - dry cleaning

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12
Q

Why are CFCs bad?

What are the equations?

A

Degrade ozone on atmosphere by decomposing to form chlorine radicals

Cl. + O3 > ClO + O2

ClO. + O3 > 2O2 + Cl.

2O3 > 3O2

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13
Q

Define alkenes

What does the bonding of alkenes involve?

A

Unsaturated hydrocarbons

Carbon Carbon double bond, a centre of high electron density

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14
Q

Result of bromine water with alkenes

A

Turns colour less

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15
Q

Define addition

A

Two molecules form one molecule

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16
Q

During electrophilic addition of HBr, what is the major product?

Why?

A

Secondary carbocation

More stable than primary carbocation

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17
Q

How is Br2 have an induced dipole dipole?

A

When Br2 is correctly orientated and due to the highly electron rich Carbon Carbon double bond

18
Q

What occurs during Hydrolysis of a hydrogen sulphate?

A

H20 if added with an acid catalyst (sulphuric acid) and an alcohol is formed

It is a reversible reaction

19
Q

How are polymers formed?

A

From alkenes and substituted alkenes

20
Q

Why do addition polymers have lower melting points than alkenes

A

Single Carbon bonds

21
Q

Why are addition ppl terms advantageous?

Why are they disadvantageous?

A

Many uses

Not biodegradable

22
Q

How is ethanol produced via hydrating?

How high is the reaction yield in this reaction?

A

Ethen is hydrated using steam in the presence of an acid catalyst at 300C to produce an alcohol

5% but when in reacted ethene gas is recycled it makes the yield 95%

23
Q

Why is oxygen in ethanol advantageous?

A

Good for complete combustion

24
Q

What is the alcohol functional group?

Why do alcohols have a high boiling point?

A

CnH2n+1OH

They undergo hydrogen bonding

25
Q

Define biofuel

A

Fuel derived from plant material

26
Q

What is the process for the fermentation of glucose?

At what temperature does fermentation occur?

What is the equation for fermentation?

A

Yeast produces enzymes in anaerobic conditions which convert glucose into ethanol + CO2 gas

30-40C

C6H12O6 > 2 C2H5OH + 2 CO2
30-40
Yeast

27
Q

What happens when solution reaches 15%

How is the percentage solution increased beyond this?

A

Yeast die. Reaction stops.

Fractional distillation is used to increase the concentration of ethanol. This takes extra time and money

28
Q

Why is fermentation advantageous?

Why is it disadvantageous?

A

It is cheap due to cheap equipment and uses sugar which is a renewable resource

Very slow
Very impure product
High labour costs

29
Q

Why is hydration of ethene advantageous?

Why is it disadvantageous?

A

RoR very fast
Pure product

Ethene is from oil which is a finite resource
It is a continuous process which requires high equipment costs

30
Q

Why are biofuels initially seen as carbon neutral?

Why is this not accurate?

A

They release the same amount of CO2 that the plants took in to produce them

Fossil fuels are burnt to power the machinery used to fertilize crops, for transporting bioethanol > prod CO2

31
Q

Why is the production of biofuels disadvantageous?

A

Land used for biofuels could be used for crops
Trees cut down for land - destroys habitats
Fertilizers pollute airways and release NO2 - greenhouse gas

32
Q

Why are biofuels advantageous?

A

Carbon neutral fuel

Renewable energy source

33
Q

What is the oxidizing agent used in the oxidation of alcohols?

What colour does it form in solution?
Why?

A

Acidified potassium dichromate VI

Bright orange

Due to presence of chromium 6+

34
Q

What is produced when primary alcohols are oxidized?

When is the first product formed?

When is the second product formed?

A

Aldehyde + h20
Or
Carboxylic acid

Minimal oxidizing agent and product is distilled immediately

Excess oxidizing agent + reflux

35
Q

Why do alcohols have higher boiling points than aldehydes?

A

Alcohols undergo hydrogen bonding
Aldehydes undergo dipole dipole bonds
Hydrogen bonding requires more energy to break as they are stronger intermolecular forces
Higher boiling point

36
Q

What happens to the oxidizing agent when the reaction is complete?

A

It is reduced and chromium becomes 3+ and turns green

37
Q

What are secondary alcohols oxidized to?

Why can they not be oxidized further?

What else cannot be oxidized for the same reason?

Why does this allow us to differentiate between alcohols

A

Ketones

No oxidizable hydrogens

Tertiary alcohols

Tertiary alcohols remain orange
Primary and secondary turn green

38
Q

Test for COOH

2 possibilities

A

Universal indicator turns red

Or

Sodium hydrogen carbonate solution causes effervescence because carbonate is neutralizing acid

39
Q

Test for aldehydes and Ketones

A

Fehlings solution - aldehyde brick red
Ketone remains blue

Tollens reagent - silver mirror when warmed with aldehydes
Remains colourless with ketone

40
Q

Define hydration

What is the reagent/ catalyst?

What is produced during elimination of an alcohol

A

Elimination of water from a compound

Concentrated sulphuric acid in my

Alkene and water

41
Q

Definition of carbon neutral

A

There is no net Carbon dioxide emission to the atmosphere

Chemistry (12 decks)

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