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Chemistry🧪 > O1: Alkenes + Alcohols > Flashcards

O1: Alkenes + Alcohols Flashcards

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1
Q

What is the alcohol functional group?

A

-OH
Hydroxyl group

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2
Q

What is the general formula for an alcohol?

A

CnH2n+1OH

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3
Q

How would you write a structural formula including an alcohol?

A

With brackets
e.g CH3CH(OH)CH2CH3

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4
Q

By what process takes a halogenoalkane to an alcohol?

A

Nucleophilic Substitution

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5
Q

What is the suffix for an alcohol?

A

-anol

e.g Butan-2-ol

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6
Q

How can alcohols be classified?

A

Primary, secondary, tertiary
-According to the number of carbons bonded to the C-OH bond
e.g P= 1 S=2 T=3

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7
Q

What is a diol?

A

An alkane where 2 of the hydrogens have been replaced by an -OH group.

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8
Q

What is the suffix of a diol?

A

-diol

e.g Hexane-2,2-diol

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9
Q

What are the properties of alcohols?

A

-All have VDW forces
-Have hydrogen bonding (very strong) between to -OH groups (the H and the O)
-The longer the carbon chain, the higher the boiling point (more VDW forces)
-Smaller ones are soluble in water as alcohols are polar due to the negative O. As chain length increases, solubility decreases as a greater region is non-polar (carbon chain)

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10
Q

What is a carbonyl group?

A

A carbonyl compound if there is a C=O in the molecule.

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11
Q

Describe Aldehydes

A

-Carbonyl group is bonded to a C and a H, or a H and a H
-They will always be on the end of a molecule
-General Formula: CnH2nO
-Structural: RCHO
-Suffix: -anal

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12
Q

Describe Ketones

A

-Carbonyl group bonded to C and C
-Always be in the middle of a molecule (position number needed)
-General formula: CnH2nO
-Structural: e.g CH3C O CH3 always after the C its bonded to
-Suffix: -anone

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13
Q

Describe Carboxylic Acids

A

-Carbonyl group bonded to a C and OH, or H and OH
-Always at the end of a molecule
-General formula: CnH2n+1COOH
-Structural: RCOOH
-Suffix: -anoic acid

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14
Q

What are the properties of Carbonyl Compounds?

A

-All have a C=O bond, O is more negative
-Aldehydes, ketones, and carboxylic acids all have VDW and dipole-dipole forces due to the negative O.
-Hydrogen bonding occurs in Carboxylic acids due to the O-H

This means:
-Aldehydes and ketones have similar MP and BP, but carboxylic acids have higher ones
-As chain length increases strength of VDW increases, so dos MP and BP

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15
Q

Are carbonyl compounds soluble?

A

-All are polar, and like dissolves like, so very soluble in water
-Smaller compounds are more soluble, larger ones less as there is a greater region of non-polar.
-Carboxylic acids are more soluble than aldehydes and ketones as they have an -OH group to form hydrogen bonds with water.

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16
Q

What do primary alcohols get oxidised to?

A

Aldehydes

Then oxidised again to carboxylic acids (as they have another C-H bond to break)

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17
Q

What are Secondary alcohols oxidised to?

A

Ketones

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18
Q

What are tertiary alcohols oxidised to?

A

Cannot be oxidised as they do not have a C-H bond to break

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19
Q

What is an Oxidising agent?

A

Accepts electrons

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20
Q

What oxidising agent is used to oxidise alcohols?

A

Acidified Potassium Dichromate (K2Cr2O7)

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21
Q

What colour does the mixture turn (alcohol) when oxidised by Acidified Potassium Dichromate?

A

Aldehydes: orange to green
Ketones: orange to green
Carboxylic acids: remain orange

22
Q

What are the methods of alcohol oxidation to the carbonyl compounds?

A

Primary: Simple distillation= aldehydes
Reflux= carboxylic acid

Secondary: Reflux= ketones

23
Q

What is Reflux?

A

Anything vapourised, condenses and returns to the mixture.

24
Q

Explain the process of oxidising alcohols

A
  1. Add excess of acidified Potassium Dichromate (that ensures we oxidise as much alcohol as possible)
  2. Heat, to increase rate of reaction
  3. Condense the carbonyl compound: ketones and carboxylic acids from above, aldehydes at the side.
25
Q

Why do the Aldehydes and Ketones vaporise before the alcohol when heated?

A

They have lower BPs as they don’t have hydrogen bonding.

26
Q

The alcohol has turned green- how do we know which is primary or secondary?

A

Add:

Tollens’ Reagent: Aldehydes= silver mirror
Ketones= no change

Fehling’s Solution: Aldehydes= blue to brick-red
Ketones= no change

27
Q

Explain the conditions of the Elimination reaction of an alcohol

A

Alcohol to alkene + water

-Also known as a dehydration reaction
-Use a Concentrated Sulphuric Acid or Phosphoric Acid catalyst (H2SO4 and H3PO4) also acts an electrophile.
-Heated

28
Q

What are 2 methods that you can produce alcohol?

A

-Hydration (addition reaction)
-Fermentation

29
Q

Explain the conditions for the hydration/addition reaction of an alcohol

A

Alkene + water = alcohol
-Reversible
-Breaks the double bond
-Uses steam
-Phosphoric acid catalyst
-Heat
-High pressure

30
Q

Hydration of ethene to ethanol for industry, conditions?

A

-Ethene comes from a fractionating column
-Phosphoric acid catalyst
-300 degrees, a compromise, higher yield with low temp as its exothermic, but decreases rate of reaction
-6000KPa as compromise, high increases yield, but expensive and dangerous

31
Q

Explain the process of fermentation

A

-Add warm water to glucose
-Add yeast (enzymes catalyse)
-No O2 in the system

32
Q

What is the fermentation equation?

A

Sugar -> ethanol + carbon dioxide

C6H12O6 -> 2 C2H5OH + 2 CO2

Ethanol is a biofuel

33
Q

What are the conditions of fermentation?

A
  • No O2, decreases yield of ethanol, or oxidise ethanol
    -Temp between 25-40 degrees
34
Q

List pros and cons of fermentation vs hydration

A

Fermentation:
Renewable
Cheaper
Lower energy

Hydration:
Faster rate of reaction
100% atom economy
Continuous process, not batch

35
Q

What is a carbon neutral fuel?

A

No overall CO2 emission into the atmosphere

36
Q

How could fermentation be a carbon neutral process?

A

Sugar cane is a plant

Photosynthesis:
6 H2O + 6 CO2 -> C6H12O6 + 6 O2

Combustion:
Fuel + O2 -> CO2 + water

CO2 balances out

Yet due to machinery, transport and fertilisers, not carbon neutral

37
Q

What is the test for a C=C bond?

A

Bromine water

Reddish-brown to colourless if C=C is present

38
Q

Inductive effect?

A

Ability of an alkyl group to stablilise a + charge as it donates electron density towards it.

39
Q

What is a nucleophile?

A

Donates an electron pair

40
Q

What is the general formula of an alkene?

A

CnH2n

41
Q

When naming an alkene with branches, what has priority?

A

-ene position number

42
Q

What are the properties of alkenes?

A

-Non-polar, so only VDW forces
-As length increases VDW strength increases due to increases in electrons, increase MP and BP
-Highly insoluble in water

43
Q

What are substituents of an E-Z isomer?

A

Atom or atoms that could be replaced by a hydrogen atom.

-so basically just not hydrogen

44
Q

How do we work out E-Z isomers?

A

-The atom with the highest Ar on each side is what we compare
-If it is a tie, e.g both are carbon, go to the next closest atom and compare Ar
-If these are also a tie, go for the 2 with the second highest Ar

45
Q

In an electrophilic addition reaction of an alkene, what can we add?

A

Halogenoalkanes : H-Br
Dihalogenoalkanes: Br-Br
Alkyl sulfates: sulphuric acid

46
Q

In electrophilic addition, and intermediate is formed, what is that?

A

A carbocation ( carbon with a + charge)

47
Q

How do you know where to put the carbocation?

A

On the most stable alkyl group.

That would be:
Primary- least stable
Tertiary- most stable

If on the stable one= major product
Not on the stable one= minor product

This is because tertiary has the most even electron density

48
Q

What is addition polymerisation?

A

Multiple monomers join to form a polymer, with smaller repeating units.

Repeating unit: smallest unit in brackets with an ‘n’ at the bottom.

49
Q

What are the properties of polymers?

A

-Strong VDW as it is long with lots of electrons
-Some may experience dipole-dipole forces and hydrogen bonding
-High MP and BP
-Inert, carbon backbone is strong and non-polar

50
Q

Why are polymers useful?

A

-Can create strong durable materials

-PVC
-Flexible if you add plasticiser which creates a space between the chain

Chemistry🧪 (15 decks)

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