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A Level Organic Chemistry > 3.5 Alcohols > Flashcards

3.5 Alcohols Flashcards

(50 cards)

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1
Q

What is the functional group of an alcohol?

A

Hydroxyl group -OH

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2
Q

What is the general formula of an alcohol?

A

CnH2n+1OH

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3
Q

How do you name alcohols

A

Hydroxyl or OH

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4
Q

What kind of intermolecular forces do alcohols have? Why?

A

Hydrogen bonding, due to the electronegativity difference in the OH bond

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5
Q

How do alcohols m.p and b.p compare to other hydrocarbons of similar C chain length? Why?

A

Higher because they have hydrogen bonding—> stronger than van der waals forces

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6
Q

Are alcohols soluble in water? Why does solubility depend on chain length?

A

Soluble when short chain - OH hydrogen bonds to hydrogen bond in water

Insoluble when long chain-non polarity of C-H bond takes precedence

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7
Q

What makes an alcohol primary?

A

C bonded to OH is only bonded to one other C atom

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8
Q

What makes an alcohol secondary?

A

C bonded to OH is bonded to two other C atoms

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9
Q

What makes an alcohol tertiary?

A

C bonded to OH is bonded to three other C atoms

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10
Q

How can ethanol be made from crude oil?

A

Hydration of ethene via electrophilic addition

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11
Q

What are the advantages and disadvantages of this method?

A

Advantages- fast, continuous process, ethanol has a high purity

Disadvantage- not renewable as from crude oil

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12
Q

How can ethanol be made by fermentation?

A

Plant carbohydrates broken down and fermented by enzymes in yeast—> ethanol

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13
Q

What conditions are needed for this reaction to take place?

A

Enzymes is yeast as catalyst 35 degree Celsius anaerobic conditions

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14
Q

Write an equation for the reaction which take place

A

C6H12O6(aq) —> 2C2H5OH + 2CO2

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15
Q

What are the advantages and disadvantages of this method?

A

Advantages - renewable as from plants
Disadvantages- slow, batch process, enzymes stop working at 15% alcohol so solution is not pure needed to be fractional distilled

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16
Q

In the future how might most ethene be made? Why is it not made like this at the moment

A

Dehydrate ethanol made by fermentation —> ethene

Not economical at the moment

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17
Q

Define carbon neutral

A

No net addition of CO2 to the atmosphere

Carbon dioxide released when combusted = carbon dioxide absorbed as a plant

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18
Q

Explain how using ethanol in petrol engines could be considered to be carbon neutral

A

Carbon dioxide released in fermentation and combustion = carbon dioxide absorbed when growing

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19
Q

Why would it probably not be entirely carbon neutral to use ethanol

A

Other “carbon costs” associated with it e.g. transport

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20
Q

What is a commercial fuel that uses ethanol? What else does it contain and why?

A

Methylated spirits- methanol (toxic-can’t be drunk)

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21
Q

Write an equation for the combustion of ethanol

Study These Flashcards
A

C2H5OH (l) + 3O2 (g) —> 2CO2(g) + 3H2O(l)

22
Q

What is an elimination reaction

Study These Flashcards
A

The removal of a smaller molecule from a larger one

23
Q

Which group leaves the parent molecule in the case of alcohols?

Study These Flashcards
A

OH and H (to form water)

24
Q

What physical conditions are needed for the elimination reaction from alcohols to alkenes? (2 alternatives)

Study These Flashcards
A

Excess hot concentrated sulphuric acid or pass vapour over hot aluminium oxide

25
Draw a mechanism for the dehydration of ethanol
Slide 52
26
Draw a method for dehydration of ethanol in the lab
Slide 54
27
What forms if you partially oxidise a primary alcohol
An aldehyde
28
What conditions are needed to partially oxidise a primary alcohol
Dilute sulphuric acid, potassium dichromate (VI), distill product as it’s produced, gentle heating
29
Write an equation for the partial oxidation of ethanol
CH3CH2OH (l) + [O] —> CH3CHO (g) + H2O (l)
30
What forms of you fully oxidise a primary alcohol
A carboxylic acid
31
What conditions are needed for this reaction
Concentrated sulphuric acid, potassium dichromate (VI), reflux done for about 20 minutes, strong heating
32
Write an equation for the full oxidation of ethanol
CH3CH2OH (l) + 2[O] —> CH3COOH (g) + H2O (l)
33
What forms of you oxidise a secondary alcohol
A ketone
34
Why can it not be oxidised further and why can’t a tertiary alcohol be oxidised
A carbon-carbon bond would have to break
35
What conditions are needed for the oxidation of a secondary alcohol
Concentrated sulphuric acid, potassium dichromate (VI), reflux for about 20 mins, strong heating
36
Write an equation for the oxidation of propan2-ol
CH3CH(OH)CH3 (l) + [O] —> CH3COCH3 (g) + H2O (l)
37
What is an aldehyde. What is its functional group?
Molecule with C=O group at the end of a carbon chain, carbonyl functional group (C=O)
38
How do you name aldehydes? Give an example
Suffix - al e.g. ethanal
39
What is a ketone? What is its functional group?
Molecule with C=O group in the middle of a carbon chain, carbonyl functional group (C=O)
40
How do you name ketones? Give an example?
Suffix -one e.g. propanone
41
What is a carboxylic acid? What is its functional group?
Molecule with a COOH group, which has to be at the end of a carbon chain Carboxyl functional group ( made up of carbonyl C=O and hydroxyl -OH group)
42
How do you name carboxylic acids? Give an example
Suffix -oic acid e.g. propanoic acid
43
What does the tollens test give a positive result for
Aldehyde
44
What is in tollens reagents? How does this react with the substance to be tested
Silver nitrate in NH3 (aq) - oxidises aldehydes but not ketones Complex silver (I) ions reduced to Ag(S)
45
How do you carry out the tollens test
Add equal volumes of substances being tested and tollens reagent to a test tube, leave in water bath for 10mins and observe any changes
46
What is the result of the tollens test for aldehydes and ketones
Aldehydes - silver mirror forms (solid Ag) Ketones - no visible change
47
What does Fehlings solution give a positive test result for
Aldehydes
48
What is in Fehlings ? How does this react with the substance to be tested?
Blue copper (II) complex ions - gentle oxidising agent Reduced to Cu+ ions (brick red)
49
What conditions do you need to use the Fehlings solution
Heat
50
What result do aldehydes and ketones give in the Fehlings test
Aldehydes - brick red ppt Ketones - no visible change

A Level Organic Chemistry (16 decks)

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