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CHEMISTRY > ORGANIC CHEMISTRY - ALCOHOLS > Flashcards

ORGANIC CHEMISTRY - ALCOHOLS Flashcards

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1
Q

what is the functional group of an alcohol?

A

-OH hydroxyl group

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2
Q

what is a general formula for an alcohol

A

CnH2n+1OH

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3
Q

how do you name alcohols (prefix and suffix)?

A

hydroxyl. - prefix
ol - suffix

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4
Q

what kind of intermolecular forces do alcohols have? why?

A

they have hydrogen bonding due to the high difference in electronegativity between O and H and vander waals forces

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5
Q

how do alcohols MP and BP compare to other hydrocarbons with the same chain length?

A

alcohols have higher MP and BP because the hydrogen bonding requires more energy to break the bonds.

Hydrogen bonding is stronger than the London forces.

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6
Q

are alcohols soluble in water? is solubility affected by chain length?

A

shorter chain alcohols are soluble in water because the OH forms hydrogen bonds with the water molecules.

Insoluble when it is a long chain due to the non polarity of the long hydrocarbon chain which takes precedence.

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7
Q

what makes an alcohol primary?

A

when the carbon attached to the OH is attached to one other carbon atom.

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8
Q

what makes an alcohol secondary?

A

when the carbon attached to the OH is attached to two other carbon atoms.

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9
Q

what makes an alcohol tertiary?

A

when the carbon attached to the OH is attached to 3 other carbon atoms.

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10
Q

how can ethanol be made from crude oil?

A

hydration of ethene via electrophilic addition (phosphoric acid catalyst.)

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11
Q

what are the advantages of this method?

A

+ fast
+ continuous

  • not renewable as made from crude oil
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12
Q

how can ethanol be made from fermentation?

A

plant carbohydrates are broken down and fermented by enyzmes in yeast = alcohols

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13
Q

what conditions are needed for fermentation to take place?

A

enzymes in yeast as catalyst
35 degrees
anaerobic conditions

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14
Q

write an equation for fermentation reaction?

A

C6H12O6 –> 2C2H5OH + 2CO2

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15
Q

advantages and disadvantages of fermentation method?

A

+ renewable as from plants
- slow batches
-slow process
- alcohol solution not pure and needs to be fractionally distilled

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16
Q

how can an alkene be made from alcohol?

A

dehydration - elimination reaction of alcohol

not economical at the moment

17
Q

what is an elimination reaction?

A

the removal of a smaller molecule from a larger one

18
Q

which group leaves the parent molecule in dehydration of alcohols?

A

OH and H to form a water

19
Q

what physical conditions are needed for the elimination reaction from alcohols to alkenes?

A

excess hot concentrated sulphuric acid

20
Q

draw a mechanism for the dehydration of alcohol

A

diagram on pmt

21
Q

what forms if you partially oxidise a primary alcohol?

A

an aldehyde

22
Q

what conditions are needed to partially oxidise a primary alcohol?

A
  • dilute sulphuric acid
  • potassium dichromate = oxidising agent
  • distill product as it is produced
  • gentle heating
23
Q

write an equation for the partial oxidation of ethanol?

A

CH3CH2OH(l) + [O] —> CH3CHO(g) + H2O(l)

24
Q

what forms if you fully oxidise an alcohol?

A

a carboxylic acid

25
Q

what conditions are needed to fully oxidise a primary alcohol?

A
  • concentrated sulphuric acid
  • potassium dichromate = oxidising agent
  • heating under reflux
26
Q

write an equation for the full oxidation of ethanol?

A

CH3CH2OH(l)+ 2[O] —> CH3COOH(g) + H2O(l)

27
Q

what forms if you oxidise a secondary alcohol?

A

a ketone

28
Q

why cant a secondary alcohol be oxidised further and why cant a tertiary alcohol be oxidised?

A

a carbon-carbon bond would have to break

29
Q

what conditions are needed for the oxidation of a secondary alcohol?

A
  • concentrated sulphuric acid
  • potassium dichromate
  • heat under reflux
30
Q

write an equation for the oxidation of propan-2-ol?

A

CH3CH(OH)CH3 (l) +[O] —> CH3COCH3 (g) + H2O

31
Q

what is an aldehyde? what is its functional group?

A

molecule with C=O group at the end of the carbon chain, carbonyl functional group (C=O)

32
Q

what is a ketone? what is its functional group?

A

molecule with C=O group in the middle of the carbon chain, carbonyl functional group (C=O)

33
Q

What does the Tollens’ test give a positive result for?

A

Aldehydes

34
Q

What is in Tollens’ reagent? How does this react with the substance to be tested?

A

Tollens’ reagent - silver nitrate
Aldehyde - oxidised to COOH, forms a silver mirror
Ketone - no silver mirror

35
Q

How do you carry out the Tollens’ test?

A

Add equal volume of substance being tested and Tollens’ reagent to a test tube. Leave in water bath for 10 mins and observe any changes.

CHEMISTRY (19 decks)

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