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Chemistry 4.0 - Core organic Chemistry > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

What are the properties of alcohols?

A
  • they contain an -OH functional group
  • the general formula is CnH2n+1OH
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2
Q

What are the physical properties of alcohols?

A
  • High melting points
  • Soluble in polar solvents
  • less volatile than their corresponding alkanes
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3
Q

What is volatility?

A

The tendency for alcohols to vapourise

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4
Q

Why do alcohols have these properties?

A
  • they have a polar O-H bond due to the difference in electronegativity of oxygen and hydrogen, this makes them soluble in polar solvents whereas alkanes are non-polar
  • Due to their OH group, alcohols have hydrogen bonds between them, as well as london forces
  • ## Hydrogen bonds require more energy to overcome, increasing their melting point and volatility compared to alkanes which only use london forces
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5
Q

Draw a hydrogen bond

A

look at notes for the answer xx

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6
Q

Why are alcohols soluble ONLY in polar solvents?

A
  • they are polar and form hydrogen bonds with polar solvents, making them more soluble
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7
Q

What affects the solubility of alcohols?

A
  • as the chain length of alcohols increases, the influence of london forces increases and the influence of the OH- bond decreases. This makes them less souble so, as chain length increases, solubility decreases
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8
Q

What is a primary alcohol?

A
  • The -OH group is attached to a carbon atom THAT is attached to two hydrogens and one alkyl group
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9
Q

Give an example of a primary alcohol and its exception
(draw both x)

A
  • Methanol is an exception
  • ethanol is a primary alcohol
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10
Q

What is a secondary alcohol?

A
  • the OH group is attached to a carbon atom THAT is attached to one hydrogen and two alkyl groups
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11
Q

What is a tertiary alcohol?

A
  • the OH group is attached to no hydrogen atoms and three alkyl groups
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12
Q

Give an example of a secondary alcohol (draw)

A
  • propan-2-ol
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13
Q

Give an example of a tertiary alcohol (draw)

A
  • 2 - methylbutan-2-ol
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14
Q

What reactions do alcohols undergo?

A
  • combustion
  • elimination
  • oxidation
  • substitution
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15
Q

Describe the combustion of alcohols and write an equation for the combustion of ethanol.

A
  • Alcohols completely burn in a plentiful supply of oxygen, forming CO2 and H20
  • this is an exothermic process
  • C2H5OH + 3O2 = 2CO2 + 3H2O
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16
Q

What is the usual oxidising mixture to oxidise a primary or secondary alcohol?

A
  • pottasium dichromate acidified with dilute sulfuric acid
17
Q

What is the colour change of potassium dichromate?

A
  • if an alcohol is oxidised, the potassium dichromate be reduced from orange to green
18
Q

What can primary alcohols be oxidised to?

A
  • aldehydes
  • carboxylic acids
19
Q

How do u prepare aldehydes?

A
  • when you heat a primary alcohol with acidified potassium dichromate an aldehyde is formed
  • to ensure that this not a carboxylic acid, the aldehyde is distilled out of the reaction mixture
  • the potassium dichromate will turn from orange to green
20
Q

GIve an example of aldehyde preparation (butan - 1 - ol)

A

Look at notes

21
Q

Draw a distillation set up

A
  • notes
22
Q

What is the general equation for the preparation of aldehydes

A
  • notes
23
Q

How do you prepare carboxylic acids?

A
  • Heat the primary alcohol strongly under reflux, this ensures any aldehydes formed undergo oxidation and form a carboxylic acid
  • Dichromate ions go from orange to green
24
Q

Give an example of this equation (butan-1-ol)

A

notes

25
Q

Draw a diagram of reflux

A
26
Q

What is the general equation of the reflux of secondary alcohols?

A
27
Q

How do you prepare ketones?

A
  • You can prepare a ketone by oxidising a secondary alcohol under reflux
  • the dichromate ions turn from orange to green
28
Q

write out the equation for the oxidation of propan - 2 - ol (secondary)

A
29
Q

What occurs when you oxidise a tertiary alcohol?

A
  • nothing, the dichromate ions remain orange
30
Q

What is dehydration?

A

-any reaction where water is removed from a starting material

31
Q

What occurs when you dehydrate an alcohol?

A
  • it forms an alkene
  • there are many products for this
32
Q

What are the conditions required to dehydrate an alcohol?

A
  • an acid catalyst
  • concentrated H3PO4
  • reflux
33
Q

What occurs during a substitution (with halide ions) reaction with an alcohol?

A
  • a haloalkane is formed
34
Q

What are the conditions to form a haloalkane from an alcohol?

A
  • heated under reflux with sulfuric acid

Chemistry 4.0 - Core organic Chemistry (8 decks)

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