O1: Alkenes + Alcohols Flashcards by Chloe Coleman

What is the alcohol functional group?

-OH
Hydroxyl group

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What is the general formula for an alcohol?

CnH2n+1OH

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How would you write a structural formula including an alcohol?

With brackets
e.g CH3CH(OH)CH2CH3

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By what process takes a halogenoalkane to an alcohol?

Nucleophilic Substitution

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What is the suffix for an alcohol?

-anol

e.g Butan-2-ol

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How can alcohols be classified?

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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What is a diol?

An alkane where 2 of the hydrogens have been replaced by an -OH group.

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What is the suffix of a diol?

-diol

e.g Hexane-2,2-diol

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What are the properties of alcohols?

-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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What is a carbonyl group?

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

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Describe Aldehydes

-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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Describe Ketones

-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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Describe Carboxylic Acids

-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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What are the properties of Carbonyl Compounds?

-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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Are carbonyl compounds soluble?

-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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What do primary alcohols get oxidised to?

Aldehydes

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

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What are Secondary alcohols oxidised to?

Ketones

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What are tertiary alcohols oxidised to?

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

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What is an Oxidising agent?

Accepts electrons

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What oxidising agent is used to oxidise alcohols?

Acidified Potassium Dichromate (K2Cr2O7)

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

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

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

Primary: Simple distillation= aldehydes
Reflux= carboxylic acid

Secondary: Reflux= ketones

What is Reflux?

Anything vapourised, condenses and returns to the mixture.

Explain the process of oxidising alcohols

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

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

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

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

Add: Tollens' Reagent: Aldehydes= silver mirror Ketones= no change Fehling's Solution: Aldehydes= blue to brick-red Ketones= no change

Explain the conditions of the Elimination reaction of an alcohol

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

What are 2 methods that you can produce alcohol?

-Hydration (addition reaction) -Fermentation

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

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

Hydration of ethene to ethanol for industry, conditions?

-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

Explain the process of fermentation

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

What is the fermentation equation?

Sugar -> ethanol + carbon dioxide C6H12O6 -> 2 C2H5OH + 2 CO2 Ethanol is a biofuel

What are the conditions of fermentation?

- No O2, decreases yield of ethanol, or oxidise ethanol -Temp between 25-40 degrees

List pros and cons of fermentation vs hydration

Fermentation: Renewable Cheaper Lower energy Hydration: Faster rate of reaction 100% atom economy Continuous process, not batch

What is a carbon neutral fuel?

No overall CO2 emission into the atmosphere

How could fermentation be a carbon neutral process?

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

What is the test for a C=C bond?

Bromine water Reddish-brown to colourless if C=C is present

Inductive effect?

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

What is a nucleophile?

Donates an electron pair

What is the general formula of an alkene?

CnH2n

When naming an alkene with branches, what has priority?

-ene position number

What are the properties of alkenes?

-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

What are substituents of an E-Z isomer?

Atom or atoms that could be replaced by a hydrogen atom. -so basically just not hydrogen

How do we work out E-Z isomers?

-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

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

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

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

A carbocation ( carbon with a + charge)

How do you know where to put the carbocation?

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

What is addition polymerisation?

Multiple monomers join to form a polymer, with smaller repeating units. Repeating unit: smallest unit in brackets with an 'n' at the bottom.

What are the properties of polymers?

-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

Why are polymers useful?

-Can create strong durable materials -PVC -Flexible if you add plasticiser which creates a space between the chain