Alcohols and Oxidation of Alcohols Flashcards

1
Q

what are the 3 types of alcohols

A

primary, secondary and tertiary

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2
Q

what does R mean?

A

repeating carbon chain

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3
Q

position of OH in primary alcohol

A

joined to the end of a carbon chain (attached to carbon with 1 other carbon bonded

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4
Q

position of OH in secondary alcohol

A

joined to an intermediate carbon atom (attached to a carbon with 2 other carbons bonded)

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5
Q

position of OH in tertiary alcohol

A

joined to an intermediate carbon which also has a branch attached (attached to a carbon with 3 other carbons bonded)

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6
Q

alternative definition of oxidation (not loss of electrons)

A

a loss of H or gain of oxygen (increasing oxygen to hydrogen ratio)

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7
Q

oxidation of primary alcohol

A

aldehyde and carboxylic acid

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8
Q

oxidation of secondary alcohol

A

ketone

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9
Q

oxidation of tertiary alcohol

A

no products formed

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10
Q

aldehyde functional group and location

A

carbonyl C=O at start-end

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11
Q

general formula of aldehydes

A

CnH2nO

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12
Q

name of aldeydes

A
  1. ends in ‘al’

2. does not contain a number to show where the functional group is because C=O is always at start

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13
Q

ketone functional group and location

A

carbonyl C=O located in the middle

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14
Q

general formula of ketones

A

CnH2nO n=3 or more

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15
Q

name of ketones

A
  1. ends in ‘one’

2. position of C=O functional group must be included in the name

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16
Q

oxidation of ethanol experiment

A
  • to facilitate oxidation reaction, an oxidising agent is used
  • superwool soaked in ethanol
  • copper oxide black –> orange/brown
  • damp pH paper turns red (ethanoic acid)
17
Q

reduction of alcohols

A

gain of H/loss of O

other way round from oxidation eg carboxylic acid –> aldehyde

18
Q

how to distinguish between aldehydes

and ketones

A

aldehydes can be oxidised to carboxylic acids but ketones cannot be oxidised further
therefore you can tell them apart by oxidation

19
Q

3 oxidising agents (tests) used to distinguish between aldehydes and ketones are:

A
  1. acidified potassium dichromate solution
  2. Fehling’s solution (aka Benedict’s solution)
  3. Tollen’s Reagent
20
Q

Tollen’s Reagent

A

colourless –> formation of a silver mirror

tollen’s made from silver ions which are reduced Ag+ (aq) +e- –> Ag (s)

21
Q

Fehling’s solution

A

blue –> brick red precipitate

Fehling’s made from copper oxide CuO Cu2+(aq) + 2e- –> Cu(s)

22
Q

Acidified potassium dichromate

A

orange –> green
Cr2O72- + 14H+ + 6e- –> 2Cr3+ + 7H2O
acidic conditions to provide H+ ions

23
Q

why would you not want something to oxidise?

A

if flavour/aroma molecules (aldehydes) are oxidised further they can change the taste and smell of the products
eg oxygen reacts with edible oils giving food a rancid flavour

24
Q

what are antioxidants?

A

molecules which will prevent oxidation reactions taking place
they are easily oxidised in place of the compounds they have been added to
can be identified as the substance being oxidised in a redox reaction

25
Q

common example of an antioxidant

A

asorbic acid (vitamin c)

26
Q

diols

A

alcohols containing two hydroxyl groups

27
Q

triols

A

alcohols containing three hydroxyl groups

28
Q

why does boiling point increase as the number of hydroxyl groups in an alcohol increase?

A

hydroxyl groups are polar and this leads to more hydrogen bonding hence more energy is needed to break them.