Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Organic Chemistry > 3.3.6 - organic analysis > Flashcards

3.3.6 - organic analysis Flashcards

(58 cards)

Start Studying
1
Q

how to distinguish aldehydes and ketone

A

aldehydes and ketones can be distinguished using oxidising agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why can aldehydes and ketones be distinguished using oxidising agents

A

aldehydes are easily oxidised but ketones aren’t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

TESTING FOR ALCOHOLS
step 1

A
  1. add 10 drops of alcohol to 2cm^3 of acidified potassium dichromate solution in a test tube
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

TESTING FOR ALCOHOLS
step 2

A
  1. warm the mixture gently in a hot water bath
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

TESTING FOR ALCOHOLS
step 3

A
  1. watch for a colour change
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

TESTING FOR ALCOHOLS
colour change for primary and secondary alcohols

A

potassium dichromate(VI) is reduced so colour changes from orange to green
- orange dichromate(VI) ions are reduced
- green chromium(III) ions are formed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

equation for reduction of potassium dichromate(VI)

A

(Cr2,O7) 2- + 6e- + 14H+ = (2Cr) 3+ + 7H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

TESTING FOR ALCOHOLS
colour change for tertiary alcohols

A

no colour change so solution stays orange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

testing for primary alcohols
(carboxylic acid)

A

if you oxidise an alcohol under reflux and it tests positive for being a carboxylic acid, then it’s a primary alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

testing for primary alcohols
(aldehyde)

A

if you oxidise an alcohol under distillation conditions and it tests positive for being an aldehyde, then its a primary alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

testing for secondary alcohols

A

if you oxidise an alcohol under reflux (or distillation) and it tests positive for being a ketone, then its a secondary alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is Fehling’s solution?

A

blue solution of complex copper(II) ions dissolved in sodium hydroxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is Benedict’s solution?

A

similar to Fehling’s but copper(II) ions are dissolved in sodium carbonate instead

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

TESTING ALDEHYDE/KETONE WITH BENEDICT’S/FEHLING’S
stage 1

A
  1. add 2cm^3 of benedict’s or Fehling’s solution to a test tube
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

TESTING ALDEHYDE/KETONE WITH BENEDICT’S/FEHLING’S
stage 2

A
  1. add 5 drops of the aldehyde or ketone to the test tube
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

TESTING ALDEHYDE/KETONE WITH BENEDICT’S/FEHLING’S
stage 3

A
  1. put the test tube in a hot water bath for a few minutes to warm it up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

TESTING ALDEHYDE/KETONE WITH BENEDICT’S/FEHLING’S
what happens if it is a aldehyde

A

benedict’s and Fehling’s solution will both reduce to a brick red Cu2,O precipitate when warmed with an aldehyde
colour change from blue to red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

TESTING ALDEHYDE/KETONE WITH BENEDICT’S/FEHLING’S
what happens if it is a ketone

A

no reaction happens with ketones so the solution stays blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

reduction of copper ions in Fehling’s/benedict’s solution

A

2(Cu)2+ + 2(OH)- + 2e- = Cu2,O + H2,O
-copper(II) ions in Fehling’s/Benedict’s solution reduced
- electrons come from oxidation of aldehyde
- copper(I) ions form a brick red precipitate of copper(I) oxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does tollens’ reagent contain

A

a [Ag(NH3)2] + complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

TESTING ALDEHYDE/KETONE WITH TOLLENS’
stage 1

A
  1. put 2cm^3 of 0.1 moldm^-3 silver nitrate solution in a test tube
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

TESTING ALDEHYDE/KETONE WITH TOLLENS’
stage 2

A
  1. add a few drops of dilute sodium hydroxide solution. light brown precipitate should form
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

TESTING ALDEHYDE/KETONE WITH TOLLENS’
stage 3

A
  1. add drops of dilute ammonia solution until the brown precipitate dissolves completely - this solution is Tollens’ reagent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

TESTING ALDEHYDE/KETONE WITH TOLLENS’
stage 4

Study These Flashcards
A
  1. add a few drops of the aldehyde or ketone and warm the solution in a water bath
25
TESTING ALDEHYDE/KETONE WITH TOLLENS' result for aldehydes
silver ions in Tollens' reagent are reduced to silver metal when warmed with an aldehyde so a silver mirror forms
26
TESTING ALDEHYDE/KETONE WITH TOLLENS' result for ketones
no change
27
equation for reduction of silver ions in tollens' reagent
Ag+ + e- = Ag -silver ions in tollens' agent reduced - electrons come from the oxidation of the aldehyde -silver comes out of solution as solid silver (silver metal)
28
TESTING FOR CARBOXYLIC ACIDS stage 1
1. add 2cm^3 of the solution you want to test to a test tube
29
TESTING FOR CARBOXYLIC ACIDS stage 2
2. add 1 small spatula of solid sodium carbonate (or 2cm^3 of sodium carbonate solution)
30
TESTING FOR CARBOXYLIC ACIDS stage 3
3. if solution begins to fizz, bubble the gas it produces through some limewater in a second test tube
31
TESTING FOR CARBOXYLIC ACIDS stage 4
4. if the limewater turns cloudy it is carbon dioxide
32
TESTING FOR CARBOXYLIC ACIDS stage 5
carbon dioxide gas should be produced if the solution was a carboxylic acid
33
TESTING FOR CARBOXYLIC ACIDS why do you have to be careful with this test
this test gives a positive result with any acid
34
TESTING FOR ALKENES what is the test testing for
unsaturated - double bonds
35
TESTING FOR ALKENES stage 1
1. add 2cm^3 of the solution you want to test to a test tube
36
TESTING FOR ALKENES stage 2
2. add 2cm^3 of bromine water to the test tube
37
TESTING FOR ALKENES stage 3
3. shake the test tube
38
TESTING FOR ALKENES stage 4
4. if alkene is present solution turns colourless, no alkenes present there is no colour change (solution stays orange)
39
what can mass spectrometry be used to find
- relative isotopic masses - abundance of different isotopes of an element - relative molecular mass (Mr) of a compound
40
how to find Mr of a compound from mass spectrometry
Mr of a compound is given by the molecular ion peak on the spectrum
41
what is the m/z value of the molecular ion peak equal to (mass spectrometry)
mass to charge (m/z) value of the molecular ion peak is equal to the Mr of the molecule
42
what are high resolution mass spectrometers capable of
high resolution mass spectrometers can measure atomic and molecular masses extremely accurately (to several DPs)
43
what is high resolution mass spectrometry useful for
useful for identifying compounds that appear to have the same Mr when rounded to the nearest whole number but actually have different Mrs to several decimal places (but still very similar)
44
what happens in infrared (IR) spectroscopy
in infrared (IR) spectroscopy, a beam of IR is passed through a sample of a chemical
45
in infrared (IR) spectroscopy, what absorbs the IR radiation
the IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy
46
in infrared (IR) spectroscopy do bonds between different atoms absorb the same or different frequencies
bonds between different atoms absorb different frequencies of IR radiation
47
bonds in different places
bonds in different places in a molecule absorb different frequencies
48
wavelength number (cm^-1) for O-H (alcohols)
3230-3550
49
wavelength number (cm^-1) for O-H (acids)
2500-3000
50
wavelength number (cm^-1) for C=O
1680-1750
51
wavelength number (cm^-1) for C=C
1620-1680
52
in infrared (IR) spectroscopy where is the fingerprint region
between 1000cm^-1 and 1550cm^-1
53
in infrared (IR) spectroscopy are fingerprint regions unique
it is unique to a particular compound
54
in infrared (IR) spectroscopy how can fingerprint regions be used to help identify compounds
you can check the fingerprint region of an unknown compound's IR spectrum against those of known compounds to help identify unknown compound
55
what does the sun emit and what is re-emitted
sun emits mainly UV/visible radiation which is absorbed by the earth's surface and re-emitted as IR radiation
56
properties of greenhouse gases' bonds
molecules of greenhouse gases e.g. CO2, methane and water vapour have bonds that are really good at absorbing infrared energy
57
how do properties of greenhouse gases' bonds impact global warming
if amount of greenhouse gases in atmosphere increases, more IR radiation is absorbed which leads to global warming
58
what does it mean for a greenhouse gas to be 'effective'
the more IR radiation a molecule absorbs, the more effective they are as a greenhouse gas

Organic Chemistry (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions